# Quantum Computing Glossary — Part 3 — H-P

The glossary is too large for a single document (over 3,000 entries), so it is divided into six parts, plus the introduction:

- Quantum Computing Glossary — Introduction.
- Quantum Computing Glossary — Part 1 — A-C.
- Quantum Computing Glossary — Part 2 — D-G.
- Quantum Computing Glossary — Part 3 — H-P. This part.
- Quantum Computing Glossary — Part 4 — Q.
- Quantum Computing Glossary — Part 5 — R-S.
- Quantum Computing Glossary — Part 6 — T-Z.

# H-P

**h.**Symbolic name for the*Planck constant*. See also:*h bar*. See Wikipediaarticle.*Planck constant***h bar.**Symbolic name for the*reduced Planck constant*— the*Planck constant*divided by two times*pi*. See also:*h*. See Wikipediaarticle.*Planck constant***H.**See*H gate*.**H gate.**See*Hadamard gate*.**Hadamard gate.**A*quantum logic gate*(*operation*) which sets the*quantum state*for a*qubit*to a*superposition*of the |0> and |1>*basis states*, so that upon*measurement*it will have an equal probability of*measuring*as a |0> or a |1>. Technically, it performs two rotations: by 180 degrees around the X-axis, which flips |1> to |0> and |0> to |1>, and then a 90-degree rotation about the Y-axis, which leaves an*input*value of |0> pointing to the front of the*Bloch sphere*or an*input*of |1> pointing to the back of the*Bloch sphere*. [TBD: verify this]. It transforms an input of |0> to 1/SQRT(2)*(|0> + |1>) and an*input*of |1> to 1/SQRT(2)*(|0> — |1>). Commonly used in conjunction with a*CNOT gate*(*controlled-NOT gate*or*controlled-X gate*—*CX gate*) to*entangle two qubits*. Abbreviated as*H gate*or*H*. See the Wikipediaarticle.*Quantum logic gate***Hadamard spread.**TBD. Referenced in thepaper by Shiekh.*The role of Quantum Interference in Quantum Computing***Hadamard transform.**Perform a*Hadamard gate*in parallel on each of*n qubits*, which places the*qubits*into a*superposition*of 2^n discrete*quantum states*. Commonly used to prepare for*quantum parallelism*, to evaluate a*computation*on all 2^n*quantum states*simultaneously. Also referred to as a*Walsh-Hadamard transform*.**Hahn echo.**See*Hahn echo experiment*.**Hahn echo experiment.**Method used to measure the*T2*time (*dephasing time*) of a*qubit*. See also:*Ramsey experiment*.**Hamiltonian.**The*operator*in*quantum mechanics*which corresponds to the total energy of a*quantum system*. See the Wikipediaarticle.*Hamiltonian (quantum mechanics)***Hamiltonian simulation.**Use of a*quantum computer*to simulate the*total energy*of a*quantum system*, such as a particle or multiple bodies in physics, or atoms and molecules in chemistry. See the Wikipediaarticle.*Hamiltonian simulation***hardware**. The electrical, magnetic, mechanical, and material*components*which are used to assemble*systems*and*devices*. Collectively, a reference to a*system*or*device*which has been constructed from*hardware components*, exclusive of any*software*which may be used on or with such*systems*and*devices*. Commonly, in the context of*quantum computing*this is simply a reference to a*quantum computer*, in contrast to any*software*that might be used on that*quantum computer*. Commonly, in a more general context, this is a synonym for a*machine*or*computer*, in contrast to the*software*that might be used on that*computer*. May include*firmware*and possibly even*operating system*and*system utilities*.**hardware architecture.**The overall, high-level*hardware design*for a*machine*,*system*, or*device*, including the*instruction set architecture*if the*system*is a*computer*.**hardware component.**An*electrical*,*electronic*,*magnetic*,*mechanical*, or*material**component*, in contrast to a*software component*. See also:*device*and*subsystem*.**hardware design.**The conception and arrangement of*electrical*,*electronic*,*magnetic*,*mechanical*, and*material**components*needed to*implement*the*hardware*for a*machine*,*system*, or*device*. The work of*electrical engineers*, including and especially*computer engineers*. See also:*hardware architecture*. Alternatively, the*process*of*designing*the*hardware*.**hardware-efficient algorithm.**An*algorithm*which is carefully designed to make the most efficient use of the available*hardware*. This will generally be different between*classical computers*and*quantum computers*, and even between particular*machine architectures*of those two categories.**hardware efficient ansatz.**See*hardware-efficient ansatz*.**hardware-efficient ansatz.**TBD. A type of*hardware heuristic ansatze*. Abbreviated as*HEA*.**hardware efficient ansatzes.**See*hardware-efficient ansatzes*.**hardware-efficient ansatzes.**Plural for*hardware-efficient ansatz*.**hardware engineer.**An*electrical engineer*or*mechanical engineer*responsible for some aspect of designing the*hardware*for a*machine*,*system*, or*device*. In contrast to*software developers*.**hardware feature.**A specific*capability*or*feature*of a specific type of*hardware*.**hardware heuristic ansatze.**TBD. Abbreviated as*HHA*. In contrast to*physically-motivated ansatze*(*PMA*).**hardware layout.**How*hardware components*and their*interconnections*are arranged on a*printed circuit board*or an*integrated circuit*.**hardware native gateset.**See*hardware-native gateset*.**hardware-native gateset.**TBD.**Hartree-Fock procedure.**TBD.**Hartree-Fock wavefunction.**TBD.**Hartree-Fock wavefunction ansatz.**TBD.**HEA.**Initialism for*hardware efficient ansatz*. See also:*HHA*and*PMA*.**heat.***Energy*which has been absorbed by*matter*or lost or dissipated from one*material*to another*material*, causing*motion*or*vibration*, which is*observed*as*heat*. See the Wikipediaarticle.*Heat***heat loss.**Loss of*energy*due to dissipation of*heat*from a*system*. Alternatively, the loss of*energy*from a*system*due to the generation of*heat*.**Heisenberg interaction.**TBD. Referenced in thepaper by Nam and Maslov, et al. See also:*Low-cost quantum circuits for classically intractable instances of the Hamiltonian dynamics simulation problem**time-dependent Heisenberg interaction*.**Heisenberg’s uncertainty principle.**With certain pairs of*quantum properties*it is not possible to measure one without disturbing the value of the other. One such pair is position and momentum. See the Wikipediaarticle. Synonym for simply*Uncertainty principle**uncertainty principle*. See also:*classical uncertainty*.**heralded controlled phase gate.**See*heralded quantum controlled phase gate*.**heralded quantum controlled phase gate.**TBD. See thepaper by Qin, Wang, Miranowicz, Zhong, and Nori. See also:*Heralded quantum controlled phase gates with dissipative dynamics in macroscopically-distant resonators**controlled phase gate*and*quantum controlled phase gate*.**hermitian operator**. See*Hermitian operator*. Should be capitalized since it is based on a name, Charles Hermite.**Hermitian operator**. A*matrix*representing an*operator*for a*vector space*which yields a*real number*. It must be a*self-adjoint operator*. In a*quantum system*, an*operator*corresponding to an*observable*must be a*Hermitian operator*, returning the real*eigenvalue*for the*eigenvector*corresponding to the*observable*. See the Wolframpage or the Wikipedia*Hermitian operator*article. See also:*Self-adjoint operator**Hermitian conjugate*.**Hermitian adjoint.**See*Hermitian conjugate*.**Hermitian conjugate.**The*transposition*of the*matrix*representing a*Hermitian operator*in which each entry is replaced with the*complex conjugate*of the corresponding entry from the original*matrix*. See the Wikipediaand*Hermitian adjoint*articles. Synonym for*Conjugate transpose**Hermitian adjoint*or*Hermitian transpose*.**Hermitian transpose.**See*Hermitian conjugate*.**Hessian information.**TBD.**heuristic.**A clever*shortcut*to a*solution*to a*problem*which bypasses most complexity and alternatives without needing to explicitly evaluate them. May yield an*approximate solution*rather than the*optimal solution*, but with significantly less effort and resources than the*optimal solution*. May not work as expected in all situations or for all cases — there are no guarantees. May not scale, or may work better at larger scale than smaller scale — may perform differently at different scales. Its appropriateness must be evaluated on a case-by-case basis.**heuristic quantum algorithm.**A*quantum algorithm*which employs the use of a*heuristic*or other form of shortcut to achieve an*approximate*,*sufficient*, or*practical solution*rather than an absolutely exact, perfectly*optimal solution*. The motivation is either speed, less resources, or simplicity of the*algorithm*.**hexadecimal digit.**A single*character*representing an*integer value*in a*4-bit integer*or*nibble*. The*characters*0 to 9 represent the*integer values*0 to 9. The letters A to F or a to f represent the*integer values*10 to 15. Two*hexadecimal digits*can be used to represent the two*nibbles*of a*byte*, and four*hexadecimal digits*can be used to represent the four*nibbles*of a*16-bit integer*. And so on, for*32-bit integers*and*64-bit integers*, and for*character strings*as well.**HHA.**Initialism for*hardware heuristic ansatze*. See also:*PMA*and*HEA*.**hierarchy of classes.**In*object-oriented programming*(*OOP*), the*subclasses*and*superclasses*of all*OOP classes*define a hierarchical ordering of the*classes*. The position of an*OOP class*in that hierarchy defines which*data items*and*functions*the*class*will have access to — all (or selected)*data items*and*functions*in that*class*and from all levels of the hierarchy above that*class*. Alternatively, the concept of a hierarchy of classes applies to any form of*class*, unrelated to*object-oriented programming*(*OOP*), also referred to as a*taxonomy of classes*.**high complexity.**A level of*complexity*which indicates that it will be difficult to comprehend and control a*system*.**high connectivity between qubits.**Exact meaning unclear. General reference to*quantum entanglement*of*qubits*in a*quantum computer*. May indicate that the*qubits*of a given*quantum computer*are collectively*highly entangled*. Conceptually, it could be*high-dimension entanglement*. [TBD: clarify this]**high degree of entanglement.**TBD.**high-dimensional entanglement.**See*high-dimensional quantum entanglement*.**high-dimensional quantum entanglement.***Quantum entanglement*when there are more than two*quantum states*per*qubit*, such that there may be more than two*entanglements*between a pair of*qubits*. Research is being pursued in this area mainly for*quantum communication*, where*channel bandwidth*is more critical.*Current quantum computers*and*near-term quantum computers*are limited to a*superposition*of two*quantum states*for a single*observable*per*qubit*.**high-dimensional quantum system.**A*quantum system*of more than two*dimensions*, such as a*quantum computer*based on*qutrits*(three*dimensions*) or*qudits*(ten*dimensions*.)**high-dimensional system.**See*high-dimensional quantum system*.**high dimensionality.**A*quantum system*with more than the two*dimensions*of each*qubit*, such as a*quantum computer*based on*qutrits*with a*dimensionality*of three or*qudits*with a*dimensionality*of ten. This concept is not utilized in*current quantum computers*or projected*near-term quantum computers*, but there is research for use in*quantum communication systems*and it might be utilized in less-near*future quantum computers*. Synonym for*higher dimensionality*.**high-end quantum computer simulator.**A*quantum computer simulator*which is running on a*high-end classical computer*, typically a*high-end server*on the Internet, such as a*cloud-based quantum service*, to boost the performance of the simulation.**high-end server.**More powerful*server*based on a*classical computer*.**high-level language.**Any*programming language*which has more expressive power than the basic*instructions*of the*machine architecture*as in an*assembly language*, including*algebraic expressions*,*data structures*, and*control structures*.**high-level programming language.**See*high-level language*.**high-level quantum language.**See*high-level quantum programming language*.**high-level quantum programming language.**A*programming language*for a*quantum computer*comparable in expressive power to the*high-level languages*of a*classical computer*. Anything above the level of an*assembly language*or a*low-level quantum intermediate representation*.**high-performance.**Relating to*high performance*.**high performance.**A level of*performance*which significantly exceeds the*performance*of a typical*computer system*or*application*.**high-performance computer.**A*classical computer*, typically a*server*, whose*performance*and*capacity*is significantly greater than for average*servers*. Generally, excludes*supercomputers*since they are their own category, far beyond even the more capable*high-performance computers*. Abbreviated as*HPC*. See the Wikipediaarticle.*Supercomputer***high-performance computing.***Classical computing*based on*high-performance computers*. Abbreviated as*HPC*. See the Wikipediaarticle.*Supercomputer***high qubit coherence.**The ability of a*qubit*to maintain its*quantum state*for more than the*execution*of a few*quantum logic gates*. Generally more than 20 microseconds.**higher-dimensional quantum system.**See*high-dimensional quantum system*. See also:*lower-dimensional quantum system*.**higher-dimensional system.**See*high-dimensional system*. See also:*lower-dimensional system*.**higher dimensionality.**See*high dimensionality*. See also:*lower dimensionality*.**higher-level language.**See*high-level language*. Alternatively, may be a more modern*programming language*which has even greater expressive power than traditional*high-level languages*.**higher-level programming language.**See*higher-level language*.**highly entangled.**Most possible pairs of*qubits*of a*quantum computer*are or can be*entangled*simultaneously, in contrast with*fully entangled*, where all possible pairs of*qubits*may be entangled,*minimally entangled*, where only a few pair of*qubits*are or can be*entangled*, or*partially entangled*, where there is no requirement that most pairs are or can be*entangled*. Technically,*highly entangled*is also*partially entangled*. [TBD: verify].**Hilbert space.**A mathematical*vector space*, which for a*quantum system*corresponds to all possible*quantum states*of the*quantum system*, such as for a*quantum computer*. A very mathematical concept which is technically true and relevant to*quantum mechanics*and*quantum computing*, but not needed for the average*user*of a*quantum computer*. See Wikipediaarticle.*Hilbert space***Hilbert space dimension.**See*Hilbert space dimensionality*.**Hilbert space dimensionality.***Dimensionality*of a*Hilbert space*— the count of*dimensions*of a*vector space*. The*dimensionality*of a*quantum system*. See thepaper by Brunner, Pironio, Acin, Gisin, Methot, Scarani.*Testing the Hilbert space dimension***holonomic.**TBD.**holonomic CNOT gate.**Short for*holonomic controlled-NOT quantum logic gate*.**holonomic CNOT logic gate.**Short for*holonomic controlled-NOT quantum logic gate*.**holonomic CNOT quantum gate.**Short for*holonomic controlled-NOT quantum logic gate*.**holonomic CNOT quantum logic gate.**Short for*holonomic controlled-NOT quantum logic gate*.**holonomic controlled-NOT gate.**Short for*holonomic controlled-NOT quantum logic gate*.**holonomic controlled-NOT logic gate.**Short for*holonomic controlled-NOT quantum logic gate*.**holonomic controlled-NOT quantum gate.**Short for*holonomic controlled-NOT quantum logic gate*.**holonomic controlled-NOT quantum logic gate.**TBD. Referenced in thepaper by Nagata, Kuramitani, Sekiguchi, and Kosaka.*Universal holonomic quantum gates over geometric spin qubits with polarised microwaves***holonomic controlled-Z gate.**Short for*holonomic controlled-Z quantum logic gate*.**holonomic controlled-Z logic gate.**Short for*holonomic controlled-Z quantum logic gate*.**holonomic controlled-Z quantum gate.**Short for*holonomic controlled-Z quantum logic gate*.**holonomic controlled-Z quantum logic gate.**TBD. Referenced in thepaper by Nagata, Kuramitani, Sekiguchi, and Kosaka.*Universal holonomic quantum gates over geometric spin qubits with polarised microwaves***holonomic CZ gate.**Short for*holonomic controlled-Z quantum logic gate*.**holonomic CZ logic gate.**Short for*holonomic controlled-Z quantum logic gate*.**holonomic CZ quantum logic gate.**Short for*holonomic controlled-Z quantum logic gate*.**holonomic CZ quantum gate.**Short for*holonomic controlled-Z quantum logic gate*.**holonomic gate.**Short for*holonomic quantum logic gate*.**holonomic gate process tomography.**TBD. Referenced in thepaper by Nagata, Kuramitani, Sekiguchi, and Kosaka.*Universal holonomic quantum gates over geometric spin qubits with polarised microwaves***holonomic H gate.**Short for*holonomic Hadamard quantum logic gate*.**holonomic H logic gate.**Short for*holonomic Hadamard quantum logic gate*.**holonomic H quantum gate.**Short for*holonomic Hadamard quantum logic gate*.**holonomic H quantum logic gate.**Short for*holonomic Hadamard quantum logic gate*.**holonomic Hadamard gate.**Short for*holonomic Hadamard quantum logic gate*.**holonomic Hadamard logic gate.**Short for*holonomic Hadamard quantum logic gate*.**holonomic Hadamard quantum gate.**Short for*holonomic Hadamard quantum logic gate*.**holonomic Hadamard quantum logic gate.**TBD. Referenced in thepaper by Nagata, Kuramitani, Sekiguchi, and Kosaka.*Universal holonomic quantum gates over geometric spin qubits with polarised microwaves***holonomic logic gate.**Short for*holonomic quantum logic gate*.**holonomic quantum computation.**TBD. Abbreviated as*HQC*. Referenced in thepaper by Nagata, Kuramitani, Sekiguchi, and Kosaka.*Universal holonomic quantum gates over geometric spin qubits with polarised microwaves***holonomic quantum gate.**Short for*holonomic quantum logic gate*.**holonomic quantum logic gate.**TBD. Referenced in thepaper by Nagata, Kuramitani, Sekiguchi, and Kosaka.*Universal holonomic quantum gates over geometric spin qubits with polarised microwaves***holonomic single-qubit gate.**Short for*holonomic single-qubit logic gate*.**holonomic single-qubit logic gate.**TBD. Referenced in thepaper by Nagata, Kuramitani, Sekiguchi, and Kosaka.*Universal holonomic quantum gates over geometric spin qubits with polarised microwaves***holonomic two-qubit gate.**Short for*holonomic two-qubit logic gate*.**holonomic two-qubit logic gate.**TBD. Referenced in thepaper by Nagata, Kuramitani, Sekiguchi, and Kosaka.*Universal holonomic quantum gates over geometric spin qubits with polarised microwaves***holonomic X gate.**Short for*holonomic X quantum logic gate*.**holonomic X logic gate.**Short for*holonomic X quantum logic gate*.**holonomic X quantum gate.**Short for*holonomic X quantum logic gate*.**holonomic X quantum logic gate.**TBD. Referenced in thepaper by Nagata, Kuramitani, Sekiguchi, and Kosaka.*Universal holonomic quantum gates over geometric spin qubits with polarised microwaves***holonomic X, Y, and Z gates.**Short for*holonomic X, Y, and Z quantum logic gates*.**holonomic X, Y, and Z logic gates.**Short for*holonomic X, Y, and Z quantum logic gates*.**holonomic X, Y, and Z quantum gates.**Short for*holonomic X, Y, and Z quantum logic gates*.**holonomic X, Y, and Z quantum logic gates.**TBD. Referenced in thepaper by Nagata, Kuramitani, Sekiguchi, and Kosaka.*Universal holonomic quantum gates over geometric spin qubits with polarised microwaves***holonomic Y gate.**Short for*holonomic Y quantum logic gate*.**holonomic Y logic gate.**Short for*holonomic Y quantum logic gate*.**holonomic Y quantum gate.**Short for*holonomic Y quantum logic gate*.**holonomic Y quantum logic gate.**TBD. Referenced in thepaper by Nagata, Kuramitani, Sekiguchi, and Kosaka.*Universal holonomic quantum gates over geometric spin qubits with polarised microwaves***holonomic Z gate.**Short for*holonomic Z quantum logic gate*.**holonomic Z logic gate.**Short for*holonomic Z quantum logic gate*.**holonomic Z quantum gate.**Short for*holonomic Z quantum logic gate*.**holonomic Z quantum logic gate.**TBD. Referenced in thepaper by Nagata, Kuramitani, Sekiguchi, and Kosaka.*Universal holonomic quantum gates over geometric spin qubits with polarised microwaves***host computer**. The*classical computer*used to control a*quantum computer*. It runs a*host program*which contains the*control logic*needed to fully*control*the*execution*of a*quantum program*.**host program.**The*code*, running on a*host computer*, a*classical computer*, which is the*control logic*which supervises, monitors, and controls the*execution*of a*quantum program*on a*quantum computer*or a*quantum simulator*. See*control logic*for details.**hosted cloud service.**See*cloud-based service*.**HPC.**Initialism for*high-performance computer*or*high-performance computing*.**HQC.**Initialism for*hybrid quantum-classical*or*hybrid quantum-classical algorithm*.**HTTP.**The*Internet protocol*for communicating over the*Internet*with a web site.**hybrid algorithm.**See*quantum hybrid algorithm*.**hybrid classical quantum algorithm.**See*quantum hybrid algorithm*and*hybrid computation*.**hybrid computation.**See*hybrid mode of operation*.**hybrid mode of operation.**A*computation*in which portions are*executed*on a*quantum computer*and portions on a*classical computer*. For example, if conditional execution, looping, function calls, or data structures and storage in files or databases are needed, such as when there is a large volume of*data*or*operations*or*logic*which are not easily represented as a*quantum logic circuit*. See thepaper by Smith, Curtis, and Zeng of Rigetti Computing.*A Practical Quantum Instruction Set Architecture***hybrid of classical computing and quantum computing.**See*hybrid mode of operation*.**hybrid quantum-classical.**An approach that uses a blend of*quantum computing*and*classical computing*, leveraging the strengths of both. Abbreviated*HQC*.**hybrid quantum-classical algorithm.**TBD. Abbreviated*HQC*.**hybrid quantum-classical algorithms for chemistry.**TBD.**hybrid quantum/classical computing.**See*quantum/classical hybrid algorithm*and*hybrid mode of operation*.**i.**Symbol used after a*real value*to indicate that it is actually an*imaginary value*.**I.**See*I gate*.**I gate.**A*quantum logic gate*which performs the*identity operation*on a*qubit*. This should not change the*quantum state*of the*qubit*, but*quantum noise*and*decoherence*may in fact change the*quantum state*.**i.i.d.**Initialism for*independent and identically distributed*. See also:*i.i.d. quantum source*.**i.i.d. quantum source.**Short for*independent and identically distributed quantum source*.**ideal logical qubit.**TBD. Referenced in thepaper by Nagata, Kuramitani, Sekiguchi, and Kosaka.*Universal holonomic quantum gates over geometric spin qubits with polarised microwaves***identical.**Two*entities*which can not be distinguished. Separate*identities*cannot be established for the*entities*.**identical matrix.**Two*matrices*which are*identical*— they have the same*dimensions*, and the same*values*for all*entries*.**identifier.**A*label*or*name*which identifies an*entity*, such as a*data item*,*function*,*variable*,*class*, or*program*. Some*identifiers*may be required to be unique, while others may be unique only within a limited*context*. See also:*proper name*.**identify.**Some*method*of determining the*identity*of an*entity*. May be via an*identifier*or by*characteristics*,*qualities*, and*attributes*.**identity.**The quality of an*entity*being*distinct*from other*entities*. May be an*individual identity*or a*group identity*. The former uniquely identifies the*individual entity*while the latter establishes*membership*in a*group*such as a*class*or*type*.**identity matrix.**The*square matrix*which when multiplied against any*square matrix*of the same*dimensions*yields that same,*identical**matrix*. Also, multiplying a*matrix*by its*inverse matrix*produces the*identity matrix*. See the Wikipediaarticle.*Identity matrix***identity operation.**Applying the*identity matrix*to the*quantum state*of a*qubit*. In theory, this should not change the*quantum state*of the*qubit*, but*quantum noise*and*decoherence*may in fact change the*quantum state*.**image.**Two-dimensional projection of a subset of a real or imaginary*physical system*as a*matrix*or*lattice*of*image elements*.**image capture.**The process of collecting all of the*image elements*for an*image*as it is*imaged*. See also:*imaging*.**image element.**The*unit*for*image capture*and*image processing*. A pixel in*classical computing*. Might*quantum computing*offer a different approach to*image elements*?**image generation.**The process of artificially constructing an*imaginary image*. See also*graphical image generation*.**image processing.***Computation*on the*image elements*of an*image*. See also:*video processing*. A very tedious and*computationally-intensive*process on a*classical computer*. Includes element-level processing, filtering, focusing, object detection and recognition, object extraction, scene recognition, feature recognition, text recognition, etc. Potential for acceleration on a*quantum computer*which could lead to whole new avenues of processing which are today unrealizable, but that would probably require a very large number of*qubits*. See also:*video processing*,*audio processing*, and*graphical image processing*.**image sensor.**A*device*(*sensor*) for capturing*images*, such as in a*digital camera*or a*digital video camera*.**imaged.***Imaging*after it has been completed.**imaginary.**See*imaginary number*.**imaginary image.**An*image*constructed or derived from human imagination, random numbers, or the output of a*model*. See also:*image generation*.**imaginary number.**A*number*which has the same form as a*real number*and a corresponding range of*values*, but is not a true*real number*. The*non-real*part of a*complex number*. It does not represent any*real quantity*. Commonly represented as a*real value*followed by the*i*symbol. See the Wikipediaarticle and the Wikipedia*Imaginary number*article.*Complex number***imaginary part.**The non-*real*portion of a*complex number*. Depending on context, this may refer to the*real value*of the*imaginary part*, or it could refer to the*imaginary part*as an*imaginary number*, which is a*real number*multiplied by the square root of minus 1 (-1). Squaring the latter would multiply the*real value*by minus 1 (-1). Unless the context is very clear, the reference is to the*real value*— the b of a + bi. See also:*real part*.**imaginary-time variational quantum simulator.**TBD.**imaginary value.**See*imaginary number*. Or an*algebraic expression*which evaluates to a*real value*, followed by the*i*symbol.**imagine.**Conceive of an*entity*independent of whether it might actually exist. See also:*contemplate*and*theorize*.**imaging.**The act of forming the two-dimensional projection for an*image*. See also:*image capture***imbalance of charge.**An*atom*which does not have a*balance of charge*— the count of*protons*is not the same as the count of*electrons*. Alternatively, the exact degree of*imbalance of charge*— the count of*protons*minus the count of*electrons*.**immunity to environmental noise.**The resilience of a*hardware circuit*or*component*in the presence of any external*electromagnetic radiation*or*magnetic fields*. May be due to*shielding*or the construction of the*device*itself. See thepaper by O’Brien, Vahidpour, Whyland, Angeles, Marshall, Scarabelli, Crossman, Yadav, Mohan, Bui, Rawat, Renzas, Vodrahalli, Bestwick, and Rigetti.*Superconducting Caps for Quantum Integrated Circuits***imperfectly implemented quantum operation.**TBD.**imperfect operation.**TBD.**imperfect quantum operation.**TBD.**implement.***Transform*an*algorithm*,*design*, or*specification*into working*code*or a*circuit*. Perform the*implementation process*.**implementation.**The result produced by the*implementation process*. Alternatively, the*implementation process*itself. The*code*is the*implementation*of the*algorithm*and*design*.**implementation process.**The*process*of*transforming*an*algorithm*,*design*, or*specification*into*code*or a*circuit*.**in silico.**Use of a*computer*to*simulate*a biological or chemical process. In contrast to a biological or chemical experiment. See the Wikipediaarticle.*In silico***in-silico VQE.**TBD.**incoherent ancilla.**TBD.**incoherent operations.**TBD.**independent and identically distributed.**TBD. Abbreviated as*i.i.d.*See also:*independent and identically distributed quantum source*.**independent and identically distributed quantum source.**TBD. Abbreviated as*i.i.d. quantum source*.**index.**Position of an*item*in a*list*, as an*integer*. Alternatively, a*data structure*which allows*data*to be*indirectly accessed*or*associatively accessed*by a*key*or*key value*.**indirect access.**A method for accessing*data*through indirect means, such as using a*key*,*index*, or*query*. See also:*associative access*.**indirectly accessed.**See*indirectly access*.**individual.**See*individual entity*.**individual entity.**An*entity**distinct*from all other*entities*, in contrast to a*group of entities*or all*entities*.**individual identity.***Identity*for an*individual entity*, as*distinct*from*group identity*.**individual member.**See*individual member of a group*.**individual member of a group.**See*individual members of a group*. An*individual*which belongs to a particular*group*.**individual members of a group.**The*individual*s who are*members*of a*group of entities*, emphasizing their*individual identity*rather than collectively as one.**individually controlled qubits.**Odd, infrequently used term, which is redundant for all*current quantum computers*, where every*qubit*can of course be individually controlled using*quantum logic gates*which can reference specific qubits.**induced error.**See*environmentally-induced error.***inductance.**Loosely, the amount of*energy*which can be stored by an*inductor*and the*frequencies*of*current*which may pass through the*inductor*.**inductor.**An*electronic component*which stores*energy*in a*magnetic field*and moderates the flow of*current*through the*device*. See the Wikipediaarticle. See also:*Inductor**inductance*and*capacitor*.**inefficiently computable function.**A*computable function*for which the length of the computation scales*superpolynomially*with the input size. In contrast to an*efficiently computable function*which scales*polynomially*with the input size.**information.***Data*which has at least some limited structure, such as*records*or*rows*in a*table*. See also:*structured information*,*semi-structured information*,*unstructured information*,*knowledge*, and*insight*. Alternatively, simply a synonym for*data*.**infrared.**See*infrared radiation*.**infrared light.**See*infrared radiation*.**infrared radiation.***Electromagnetic radiation*which is just below the threshold for visible red*light*, with a slightly lower*frequency*and slightly longer*wavelength*. People cannot directly see*infrared radiation*, but they can feel it as heat. See the Wikipediaarticle. Shortened as*Infrared**infrared*. Abbreviated as*IR*. See also:*ultraviolet radiation*.**inherent computational advantage.**For a*quantum computer*,*superposition*and*entanglement*of*quantum states*provide a degree of parallelism which is inherently superior to the capabilities of a*classical computer*. Alternatively, simply the fact that some*quantum computers*have enough*qubits*that they can no longer be simulated on a*classical computer*for a broad class of*quantum algorithms*.**inherit.**In*object-oriented programming*(*OOP*), a*subclass*is granted access to all (or some) of the*data items*and*functions*of its*parent class*and the*superclasses*of its*parent class*. It*inherits*that access.**inheritance.**In*object-oriented programming*(*OOP*), the fact that a*subclass*has access to*data items*and*functions*of its*parent class*and any*superclasses*of its parent class. Those*data items*and*functions*are*inherited*from the*superclasses*. See also:*multiple inheritance*.**inherited.**In*object-oriented programming*(*OOP*), the*data items*and*functions*of the*parent class*of a*subclass*and the*superclasses*of its*parent class*to which the*subclass*will be granted access. It*inherited*that access.**initial state.**The desired*state*of a*system*when in comes into existence or*processing*begins. See also:*final state*. There may be a*default*or the*user*may be required to specify the*state*.**initial value.**The desired*value*of a*variable*when a*program*or*object*comes into existence or when*processing*begins. There may be a*default*or the*user*may be required to specify the*value*.**initialization.***Processing*which must be performed before a*system*can begin its normal*processing*, such as to*initialize*both*state*and*variables*.**initialize.**To provide the*initial value*for a*variable*or the*initial state*of a*system*.**inner degree of freedom.**TBD. Referenced in thepaper by Nagata, Kuramitani, Sekiguchi, and Kosaka.*Universal holonomic quantum gates over geometric spin qubits with polarised microwaves***inner product.**TBD. See also:*dot product*. See the Wolfram MathWorldpage.*Inner Product***inner product space.**A*vector space*which provides an*inner product*. See the Wikipediaarticle.*Inner product space***inner-product space.**See*inner product space*.**input.**See*input value*. Alternatively,*input data*— all*input values*to be provided to an*entity*so that it can*process*them, as well as*configuration parameters*. See also:*output*.**input data.**All*input values*to be provided to an*entity*so that it can*process*them. Synonym for*input*. See also:*configuration parameter*and*output data*.**input value.**A*data value*or*signal*to be provided to a*system*,*application*,*component*,*device*,*process*,*function*,*mapping*, or*code*so that it can perform its processing. See also:*argument*and*output value*.**insight.**A deep, intuitive, nuanced, and enlightening understanding of some matter, especially if it unlocks doors and sheds light on other matters, in contrast to simply superficial*knowledge*. Can*quantum computers*help us gain*insight*?**instruction.**The*classical computing*equivalent of a*quantum operation*or a*quantum logic gate*. The equivalent of a*sequence of instructions*for a*classical computer*would be a*quantum circuit*on a*quantum computer*.**instruction set.**See*instruction set architecture*.**instruction set architecture.**A*detailed specification*of the set of*operations*or*instructions*that a*computer*can*execute*, including any internal data and control resources, such as*registers*and*memory*which can be*accessed*by those instructions, as well as any*data formats*which are relevant to both*instructions*and internal data and control resources. Either a*classical instruction set architecture*or a*quantum instruction set architecture*. Both overview and details for an*instruction set architecture*would be found in a*principles of operation*document.**insulating substrate.**The surface on which the*electronic components*and*interconnections*of an*integrated circuit*are*fabricated*. This surface is*electrically neutral*, an*insulator*, assuring that*electric charge*can only move between electronic components via explicit*interconnections*. Can be abbreviated simply as*substrate*.**insulator.**A*material*which is*electrically neutral*and inhibits the transmission of*electric charge*, with the exception of a*Josephson junction*which permits the*tunneling of electrons*through an*insulator*, but in a controlled fashion. In contrast to a*conductivity*, which facilitates*transmission*of*electric charge.***integer.**The normal mathematical meaning — a*whole number*, a*number*without a*fraction*. See also:*real*,*complex number*. See the Wikipediaarticle.*Integer***integer factorization.**See*integer factorization problem*.**integer factorization problem.**The*problem*of finding the collection of*integers*whose product is a given*integer*. The values in that collection are are not necessarily*prime numbers*(other than the degenerate sequence of 1 and the number itself.) See the Wikipediaarticle. Required for*Integer factorization**cryptography*which is based on*keys*which are large*prime numbers*. See also:*prime factorization problem*.**integer number.**A*number*which is an*integer*. It has no*fractional digits*.**integer value.**A*value*which is an*integer*.**integrated circuit.**One or more*electronic circuits*whose*electronic components*and*interconnections*have been*fabricated*onto an*insulating substrate*, in contrast to a*printed circuit board*containing*discrete electronic components*— and*integrated circuits*as well. The*substrate*will then be placed in some type of*chip package*which can then be inserted or otherwise fastened onto a*printed circuit board*. Abbreviated as*IC*. Commonly referred to as a*chip*. See the Wikipediaarticle.*Integrated circuit***integrated fabric of programmable quantum devices.***Qubits*arranged in a*grid*or*lattice*(*fabric*) which facilitates*coupling*between*qubits*. The*qubits*themselves may be arranged in a*grid*, or they may be lined on the edges of the*grid*and it is the*interconnections*which comprise the*grid*. Marketing term used by D-WAVE Systems in their.*The D-Wave 2000Q™ Quantum Computer Technology Overview***interconnections.**The*connections*between*electronic components*of an*electronic circuit*, especially on an*integrated circuit*, but on a*printed circuit board*as well. Alternatively, references or includes*cables*,*wiring*,*waveguides*, and*wireless connections*as well when considered a larger*system*, multiple*systems*, or*remote devices*.**interference.**See*quantum interference*. TBD.**intermediate format.**A*data format*between a*source format*and a*final format*. There may be any number of such*intermediate formats*, such as one for each*step*or*stage*of*transformation*or*processing*, each of which performs a*transformation*of*data*,*information*, or*code*to either a different*data format*or a modified version of the same*data format*. Synonym for*intermediate representation*.**intermediate measurement.***Measurement*performed before the completion of a*quantum circuit*. The*outcome*of the*intermediate measurement*may be used to influence the choice of what*quantum logic gates*will follow. See also:*quantum intermediate measurement*.**intermediate representation.**A*data format*which is a*transformation*of an original,*source format*of*data*or*code*, but not the*final format*which can be directly*processed*by its intended destination — it will need to be*transformed*again before it can be directly*processed*. Abbreviated as*IR*. An*IR*can be used as a*common format*so that a variety of different*tools*can operate on the*IR*without knowledge of the final*format*, which may be too esoteric or*machine-specific*to present an opportunity for wide sharing of the tool. For example, a*programming language compiler*could be applicable to more than one type of*machine*by*transforming*the*source code*for the*program*into an*intermediate representation*which is independent of the type of*machine*, which can then be*transformed*by other*tools*into the*code format*needed for*executable code*for the*target machine*.**Internet protocol.**A*protocol*for communicating with an*Internet service*, such as*HTTP*for web sites.**interpreter.**See*virtual machine*.*Software*which can*execute*a*program*without the need to*compile*it into*machine language*. Common for more*specialized programming languages*which are either too complex for direct*compilation*to*machine language*or used for purposes where the raw speed of*machine language*is not strictly needed. See also:*simulator*.**inter-process communication.**See*interprocess communication*.**interprocess communication.**A m*ethod*for passing*information*between two*processes*. See also:*process synchronization*. See the Wikipediaarticle.*Inter-process communication***interval.**A gap or*period*of*time*or*space*. May be a*discrete interval*or a*continuous interval*.**interval of time.**A gap or*period*of time. Generally, of fixed length. Generally, repeated. Alternatively, a particular*period*in*time*. Either a*discrete interval of time*or a*continuous interval of time*.**intractable.**Current*methods*and*technologies*are unable to cope. See also:*intractable problem*.**intractable problem.**A*problem*for which current*methods*and*technologies*are unable to arrive at a*solution*. Alternatively, a*solution*can be found, but the cost or other criteria might make it unacceptable.**introduction to quantum computing.**See*first introduction to quantum computing*.**ion.**A*particle*, either an*atom*or*molecule*, which acts as a*charged particle*as a result of losing one or more of its*electrons*or gaining extra*electrons*, such that the number of*protons*and*electrons*of the*particle*are not equal. It may have a*net positive charge*or a*net negative charge*, depending on whether it has a deficit or surplus of*electrons*. See the Wikipediaarticle.*Ion***ion trap.**Any*method*of capturing and containing a*charged particle*(*ion*) using*electrical or magnetic fields*. Can be used to construct a*qubit*for a*quantum computer*. See Wikipediaarticle. Also known as*Ion trap**trapped ion*. See*trapped Rydberg ion*.**ion trap quantum computer.**Any*quantum computer*whose*qubits*are based on*ion traps*. See the Wikipediaarticle. Also known as*Trapped ion quantum computer**trapped-ion quantum computer*. See*trapped Rydberg ion quantum computer*.**ion trap quantum computing.***Quantum computing*on an*ion trap quantum computer*. Technically, algorithms should not be so different from algorithms on any other*gate-based quantum computer*.**ion trap qubit.**A*qubit*based on an*ion trap*. See*trapped Rydberg ion qubit*.**ion-trapped quantum computer.**See*ion trap quantum computer*.**IPEA.**Initialism for*iterative quantum phase estimation algorithm*.**IR.**Initialism for*intermediate representation*,*infrared*, or*infrared radiation.***Ising coupling.**TBD. See thepaper.*Robust Ising Gates for Practical Quantum Computation***Ising (XX) gate.**TBD. See thepaper. See the Wikipedia*Robust Ising Gates for Practical Quantum Computation*article, but even it is vague.*Quantum logic gate***Ising (zz) coupling gate.**TBD. See thepaper.*Robust Ising Gates for Practical Quantum Computation***Ising interaction.**TBD. See thepaper.*Robust Ising Gates for Practical Quantum Computation***isolation.**Quality of a*system*that its*state*is not dependent on or impacted by the*surrounding environment*. This quality is achieved and maintained by*shielding from stray electromagnetic radiation*, physical separation, and low*energy*and low*temperature*.**item.**An*object*or*value*. See*data item*or*list item*. Synonym for*element*.**Iteration.**A repetition of something, such as*execution*of*code*or*execution*of a*quantum logic circuit*, or any arbitrary*process*. Alternatively, the general process of*iterating*or repeating some sort of*processing*.**isolated.**Not in direct contact with or affected by the*surrounding environment*.**isolated quantum system.**Redundant term — all*quantum systems*are presumed to be*isolated*, otherwise they would not be considered true, complete*systems*. The un-isolated*system*would need to be expanded until it was essentially*isolated*from any*surrounding environment*. See*quantum system*.**iSwap.**See*ISWAP*.**ISWAP.**See*ISWAP gate*.**iSwap gate.**See*ISWAP gate*.**ISWAP gate.**A*quantum logic gate*which swaps the*quantum state*of two*qubits*plus a*phase shift*— applying a minus*i**phase shift*to the first*qubit*if it is in the |1>*basis state*and applying a minus*i**phase shift*to the second*qubit*if it is in the |0>*basis state*. Abbreviated as*ISWAP*. Use the*PSWAP gate*to apply a more specific*phase shift*angle. [TBD: 1) is it a shift of phase or a setting of phase and 2) is the condition before the swap or of the state being swapped in?] Referenced infrom Rigetti Computing. See also:*Source Code Documentation — pyquil.api**SWAP gate*,*CSWAP gate*, and*PSWAP gate*.**iterative quantum phase estimation algorithm.**TBD. Abbreviated as*IPEA*.**joint state.**TBD.**Jordan-Wigner encoding.**TBD.**Jordan-Wigner mapping.**TBD.**Jordan-Wigner representation.**TBD.**Jordan-Wigner transform.**TBD.**Jordan-Wigner transformation.**TBD.**Josephson effect.**The effect of*quantum mechanics*which enables*electrons*to*tunnel*across an*insulator*placed between two*superconductors*.*Josephson junctions*are*electronic devices*which exploit this effect. See the Wikipediaarticle. See also:*Josephson effect**quantum transistor*.**Josephson junction.**An*electronic component*which exploits the*Josephson effect*. Commonly used to construct a*superconducting quantum computer*. Commonly a*pi Josephson junction*. See the Wikipediaarticle.*Pi Josephson junction***KAK coefficients.**TBD.**KAK form.**TBD.**KAK interaction coefficients.**TBD.**ket.**Used to describe a*quantum state*. The*Hermitian conjugate*of the*bra*of a*bra-ket*. Represents a*column vector*. See*bra-ket notation*. See also:*bra*and*Dirac notation*. For example, |0> and |1> are*kets*, as are |101> and |001011>.**ket notation.**See*ket*and*bra-ket notation*. Those are the two proper terms — there is no separate*ket notation*.**key.**May be an*encryption key*to control access to*data*or a*key value*used to indirectly access*data*. See also:*cryptographic key*and*public-key cryptography*.**key value.**A*value*which uniquely*identifies*a particular collection of*data items*in a larger collection of*data*, permitting the*data items*to be indirectly accessed.**keyword.**A simple*natural language word*, although the exact*syntax*may be more specialized than simply letters. Alternatively, a subset of*words*which have special or at least more significant*meaning*than most other*words*.**keyword search.***Search*that is optimized for*words*,*keywords*, and*phrases*in*natural language text*or in any*textual value*which has a*syntax*which represents*words*or*keywords*. See also:*search engine*.**KLM quantum computation.**Short for*Knill-Laflamme-Milburn quantum computation*.**Knill-Laflamme-Milburn type quantum computation.**See*Knill-Laflamme-Milburn-type quantum computation*.**Knill-Laflamme-Milburn-type quantum computation.**See*Knill-Laflamme-Milburn quantum computation*.**Knill-Laflamme-Milburn quantum computation.**TBD. Read thepaper by Knill, Laflamme, and Milburn.*Efficient Linear Optics Quantum Computation***knowledge.**Understanding of some matter, from basic facts, to simple and complex*relationships*, to general principles, in contrast to simply*data*and simple*information*. See also:*insight*. Can*quantum computers*help us expand our*knowledge*? Can*quantum computers*consume and express*knowledge*, in contrast to simply*data*?**Kronecker product.**The*outer product*of two*matrices*, which produces a larger*matrix*with*dimensions*which are the product of the original*dimensions*— m x n times p x q produces an mp x nq*matrix*. See Wikipediaarticle. Synonym for*Kronecker product**tensor product*.**label.**A*name*used to*identify*an*entity*, possibly to indicate its*type*, ownership, or other association.**language.**The*class*of*expressions*which can be constructed according to the*syntax rules*of a*grammar*, such that an*automaton*or*state machine*constructed according to the*syntax rules*of the*grammar*is capable of recognizing the structure, detail, and meaning of those*expressions*. Includes*natural languages*,*programming languages*, and*specialized languages*.**large problem.**Vague notion of a*problem*of significant size. Size is in the eye of the beholder. Simply in contrast to tiny, small, modest, and moderate or medium size. Towards the higher end of the spectrum of*problem*sizes.**large-scale quantum computer.**May simply be a synonym for a*general purpose quantum computer*, with emphasis on it’s*capacity*to handle*large problems*. Could conceivably be a*fixed-function quantum computer*, emphasizing its*capacity*but not its*range of function*. Alternatively, simply a synonym for*large-sized quantum computer*, based on*qubit count*.**large-scale quantum computing.***Computing*using a*large-scale quantum computer*.**large-scale quantum processor.**TBD.**large-scale universal quantum computer.***Large-scale quantum computer*with emphasis on its ability to be applied to a wide*range of problems*, in contrast to a*fixed-function quantum computer.*A*general purpose quantum computer*, with emphasis on it’s*capacity*to handle*large problems*. If the terms are being used properly,*universal*emphasizes the ability to perform any*operation*of a*classical computer*, again in contrast to a*fixed-function quantum computer*. See also:*large-sized quantum computer*.**large-scale quantum information network.***Quantum communication*with a significant number of*stations*over an extended geographical area.**large-sized quantum computer.**Vague definition of the usability of a*quantum computer*in terms of its*qubit count*. Currently, 50*qubits*would be considered a*large-sized quantum computer*. Less than that would be a*medium-sized quantum computer*,*modest-sized quantum computer*, or a*small-sized quantum computer*. Different individuals and organizations might quibble over these numbers and characterizations. These numbers will rise each year as more*qubits*become available. In two years, 50 to 100*qubits*will likely be considered a*medium-sized quantum computer*and 128, 192, or 256*qubits*would be considered a*large-sized quantum computer*. In five years, the number for large-sized might be 1024, 2048, 4096, or even 8192, depending on the pace of*hardware*advances.**lattice.**A two or three-dimensional*regular*arrangement of objects of any type, commonly*atoms*,*ions*, and*molecules*. See also:*crystal*and*crystalline structure*. See the Wikipediaarticle. Alternatively, such an arrangement of larger objects, such as*Lattice (group)**computer systems*or*processors*within a*multiprocessor computer system*. See also:*grid*and*fabric*.**lattice problem.**TBD. See the Wikipediaarticle.*Lattice problem***LC.**Initialism for*local Clifford*.**LC equivalence.**Short for*local Clifford equivalence*.**LC equivalent.**Short for*local Clifford equivalent*.**LC group.**Short for*local Clifford group*.**LC operations.**Short for*local Clifford operations*.**leaf.**See*leaf node*.**leaf node.**A*node*in a*graph*, especially a*tree*, which has no relationship to other*nodes*as subsidiary*nodes*, in contrast to a*branch node*. A*leaf node*is subsidiary to a*branch node*or the*root node*.**leakage.**TBD.**leakage error.**TBD.**learning.**The*process*of acquiring*knowledge*about a*technology*, typically through*training*, reading, and*experimentation*.**leaves.**See*leaf node*.**library.**See*software library*.**lifting.**TBD. Referenced in thepaper by Smith, Curtis, and Zeng of Rigetti Computing.*A Practical Quantum Instruction Set Architecture***light.***Electromagnetic radiation*which is visible to the unaided human eye. In some contexts, it may also include*infrared*and*ultraviolet*. Alternatively, simply a reference to*photons*.**linear algebra.**A*mathematical framework*which is the core*mathematics*required to model*quantum mechanics*, and hence*quantum computers*, including*vector spaces*and*linear combinations*that model*superposition*.*Quantum states*are modeled with*eigenstates*,*linear combinations*of*eigenvalues*and*eigenvectors*. Not to be confused with*elementary, basic high school algebra*. See the Wikipediaarticle.*Linear algebra***linear combination.**In*linear algebra*, two or more*vectors*can be combined into a single*vector*by adding the*vectors*, each multiplied by a*constant*or*weight*. The*vectors*are also known as*eigenvectors*or*basis vectors*. The*weights*are also known as the*eigenvalues*for the*eigenvectors*. Alternatively, each*vector*can be decomposed into a*linear combination*of the*basis vectors*for the*vector space*and then the two*vectors*can be added by adding the two*linear combinations*of*basis vectors*, weighted as desired. In*quantum mechanics*, two or more*quantum states*(*vectors*) can be combined into a single*quantum state*(*vector*) by adding the*quantum states*(*vectors*), each multiplied by a*constant*or*weight*. Alternatively, each*quantum state*can be decomposed into a*linear combination*of the*basis states*of the*quantum system*and then the two*quantum states*can be added by adding the two*linear combinations*of*basis states*, weighted as desired. The*weights*for a*quantum system*will be the*amplitude*or*probability amplitude*for the*basis state*or*eigenvector*. The*weight*is the*eigenvalue*for the*eigenvector*(*basis state*.) The*probability*for the*basis state*is the square of the*modulus*of the*amplitude*(*probability amplitude*) — the sum of the squares of the*real part*and the*imaginary part*of the*complex number*representing the*probability amplitude*. See also:*superposition*and*eigenvalues and eigenvectors*.**linear complexity.**An*algorithm*whose*computational complexity*is proportional to the size of its*input*—*O(n)*. See also*polynomial complexity*,*exponential complexity*, and*quadratic speedup*.**linear ion chain.**TBD. Relevant to a*trapped-ion quantum computer*.**linear momentum.**Product of the*velocity*and*mass*of an*object*. See the Wikipediaarticle. Commonly shortened as*Momentum**momentum*. See also:*angular momentum*.**linear optical quantum computing.**A theoretical approach to*quantum computing*based on*photons*for*qubits*. Abbreviated as*LOQC*. See the Wikipediaarticle and read the*Linear optical quantum computing*paper by Knill, Laflamme, and Milburn. See also:*Efficient Linear Optics Quantum Computation**Knill-Laflamme-Milburn quantum computation*,*KLM quantum computation*, and*boson sampling*.**linear optics quantum computation.**See*linear optical quantum computing*.**linear space.**See*vector space*.**linear vector space.**See*vector space*.**linguistic element.**One of the*elements*used to define a*language*with a*grammar*. Either a terminal symbol or a non-terminal symbol. The former can be a*word*,*term*,*token*,*number*,*punctuation*, or a*character sequence*. The latter is the*name*or*identifier*which*identifies*a*syntax rule*in the grammar. See the Wikipediaarticle.*Backus–Naur form***liquid.***Matter*which flows freely. See also:*liquid*,*gas*, and*plasma*.**liquid matter.**See*liquid*. See also:*solid matter*,*gaseous matter*, and*plasma matter*.**liquid medium.**A*medium*comprised of*liquid*, in contrast with*solid medium*,*gaseous medium*, or*plasma medium*. See also:*liquid matter*.**list.**A*data structure*representing a sequence of*data items*—*list items*, in order, each having an*index*, with the first*item*being at*index*0 and the last*item*being at*index**n*minus 1, where*n*is the number of*items*in the*list*. Alternatively, some*systems*,*software*, or*programming languages*may use*indexes*in the range of 1 to*n*. A*list*may be a*fixed length list*or a*dynamic list*. In the case of a*dynamic list*, there will be special*functions*to*query*the current size of the*list*, to add a new*item*to the end of the*list*, to insert an*item*in the middle of the*list*, and to remove an*item*from any position in the*list*. See also:*list item*.**list item.**An*item*, a*data item*, in a*list*or*queue*. Generally, an*object*or*value*. Synonym for*element*.**local Clifford.**TBD. Abbreviated as*LC*. See also:*local Clifford group*and*local Clifford equivalence*.**local Clifford equivalence.**TBD. Shortened as*LC equivalence*. See*local Clifford group*.**local Clifford equivalent.**TBD. Shortened as*LC equivalent*. See*local Clifford group*.**local Clifford group.**TBD. See thepaper by Van den Nest, Dehaene, and De Moor*An efficient algorithm to recognize local Clifford equivalence of graph states***local Clifford operations.**TBD. Shortened as*LC operations*. See*local Clifford group*.**local gradient.**TBD.**local hidden variables.**See*local hidden variable theory*.**local hidden variable theory.**An attempt to explain*quantum mechanics*without the need for*probability*by presuming that there is additional*state*, the*local hidden variables*, which accounts for the apparent*probabilities*of*quantum states*. See the Wikipediaarticle. See also:*Local hidden variable theory**quantum nonlocality*.**local simulator.**See*local quantum simulator*.**local quantum simulator.**A*quantum simulator*running on the*user*’s*computer*. See also:*remote quantum simulator*.**local unitary.**TBD. Abbreviated as*LU*. See also:*local unitary equivalence*.**local unitary equivalence.**TBD. Shortened as*LU equivalence*. See thepaper by Kraus.*Local unitary equivalence and entanglement of multipartite pure states***local unitary equivalent.**TBD. See*local unitary equivalence*.**local unitary operations.**TBD. See also:*local unitary equivalence*.**logic.**May be*algorithm*,*software code*,*code*, or*quantum logic*. Alternatively,*Boolean logic*.**logic gate.**See*quantum logic gate*. Alternatively, a*digital electronic component*, such as in a*classical computer*.**logic gate execution.**See*quantum logic gate execution*.**logic gate instruction set.**See*quantum instruction set*.**logical gate.**See*logic gate*.**logical qubit.**See*quantum logical qubit*. An ideal*qubit*as seen from the perspective of a*quantum instruction set architecture*,*quantum program*,*programmer*, or*user*, in contrast to a*physical qubit*in the underlying*hardware*.*Error correction schemes*may require multiple*physical qubits*to implement each*logical qubit*. See also:*quantum logical gate*. Synonym for*computational qubit*.**longitudinal coherence time.**TBD.**LOQC.**Initialism for*linear optical quantum computing*.**low-depth quantum circuit.**A*quantum circuit*with only a relatively small*gate count*. Synonym for*short-depth quantum circuit*and*shallow circuit.***low-dimensional quantum system.**See*lower-dimensional quantum system*.**low-dimensional system.**See*lower-dimensional quantum system*.**low dimensionality.**See*lower-dimensionality*. In contrast to*high dimensionality*.**low-level quantum intermediate representation.**See*intermediate representation*, in contrast to a*high-level quantum programming language*. Referenced in thepaper by Smith, Curtis, and Zeng of Rigetti Computing. Shortened as*A Practical Quantum Instruction Set Architecture**low-level quantum IR*. The*QUIL*language, as described in that same paper, refers to itself as a*low-level quantum IR*with*classical*control.**low-level quantum IR.**Shorthand for*low-level quantum intermediate representation*.**low-noise quantum computer.**TBD. In contrast to*noisy intermediate-scale quantum computer*. See also:*lower noise solid state quantum computer*. See thepaper by Nersisyan, Poletto, Alidoust, Manenti, et al of Rigetti Computing.*Manufacturing low dissipation superconducting quantum processors***lower-dimensional quantum system.**A*quantum system*with*lower dimensionality*. Relative concept, simply to suggest fewer*dimensions*than a*higher-dimensional quantum system*. Alternatively, a reference to a two-*state**quantum system*, such as a*qubit*, or a*quantum computer*constructed with*qubits*.**lower-dimensional system.**See*lower-dimensional quantum system*.**lower dimensionality.**A relative concept, simply to suggest fewer*dimensions*than*higher dimensionality*. Alternatively, a*dimensionality*of two.**lower noise solid state quantum computer.**TBD. In contrast to*noisy intermediate-scale quantum computer*. See also:*low-noise quantum computer*. See thepaper by Nersisyan, Poletto, Alidoust, Manenti, et al of Rigetti Computing.*Manufacturing low dissipation superconducting quantum processors***LU.**Initialism for*local unitary*.**LU equivalence.**Short for*local unitary equivalence*.**LU-equivalence.**Short for*local unitary equivalence*.**LU equivalent.**Short for*local unitary equivalent*.**LU-equivalent.**Short for*local unitary equivalent*.**LU operations.**Short for*local unitary operations*.**machine.**Synonym for*computer*, but emphasizing the*hardware*.**machine architecture.**Overall*architecture*and*design*for a*machine*or*computer*. Includes or may specifically refer to the*instruction set architecture*for the*machine*, although an*instruction set architecture*may apply to more than one*machine architecture*, in whole or in part. For example, two or more*machine architectures*in a*family of machine architectures*may have identical*instruction set architectures*, with the exception of the number of*qubits*, or additional or less specific*hardware features*, even though the*logic gates*(*instructions*) supported by the*instruction set*are identical.**machine language.**See*instruction set architecture*. The*instructions*or*operations*which can be directly*executed*by a*computer*, in contrast to the*higher-level programming languages*which most*software developers*use to write*programs*. See also:*assembly language*, which is commonly used as a synonym.**machine language instruction.**See*instruction.*Redundant —*instruction*always means at the level of*machine language*, in contrast to*operations*,*expressions*, and*statements*which are at the level of*source code*for a*high-level language*.**machine learning.**See the Wikipediaarticle. See also:*Machine learning**artificial intelligence*and*quantum machine learning*.**machine learning algorithm.***Algorithm*focused on*machine learning*. See also:*quantum machine learning algorithm*.**machine level programming.**See*machine-level programming*.**machine-level programming.***Coding*in*assembly language*at the level of individual*instructions*or*operations*. For a*quantum computer*, in a*quantum assembly language*at the level of individual*quantum logic gates*.**machine-specific.**Some element of*code*,*data*, or*machine architecture*which applies to a particular type of*machine*and is not shared by other types of*machines*.**magnetic field.**TBD. see the Wikipediaarticle. See also:*Magnetic field**electric field*and*electromagnetic field*.**magnetic quanta.**TBD.**magnitude.**Size of a*quantity*or*absolute value*of a*number*, independent of*sign*or*direction*.**main diagonal.**See*main diagonal of a matrix*.**main diagonal of a matrix.**The*entries*of a*matrix*along the*diagonal*from the upper-left corner, in contrast to the*antidiagonal*which are*entries*along the*diagonal*from the upper right corner. If the*matrix*is not square,*entries*on the*diagonal*which would be outside the*matrix*will be treated as if they were zero. See the Wikipediaarticle. See also:*Main diagonal**diagonal of a matrix*.**main memory.**The primary*memory*which is used to store*data*during*execution*of a*computer program*. See also:*mass storage*. At the present,*quantum computers*have no*main memory*.**main processor.**The primary*processor*on a*computer*where*application programs*are*executed*. There may be*secondary processors*,*auxiliary processors*, and*coprocessors*as well, but they are for use by specialized*software*rather than for*programs*developed by*users*. In a*multiprocessor computer system*, one of the*processors*will be the*main processor*, controlling the overall*computer system*, and*application programs*can be*executed*on any of the other*processors*in addition to the*main processor*. See also:*central processing unit*,*multiprocessor*,*coprocessor*,*adjunct processor*,*auxiliary processor*,*secondary processor*,*parallel processor*, or*graphics processor*.**Majorana.**TBD. See also:*Majorana-based quantum computer*.**Majorana-based fermionic quantum computation.**TBD. See also:*Majorana-based quantum computer*.**Majorana-based quantum computer.**TBD.**Majorana bound state.**TBD. See also:*Majorana-based quantum computer*.**Majorana fermion.**TBD. See also:*Majorana-based quantum computer*.**Majorana fermion bound state.**TBD. See also:*Majorana-based quantum computer*.**Majorana mode.**TBD. See also:*Majorana-based quantum computer*.**Majorana particle.**TBD. See also:*Majorana-based quantum computer*.**Majorana quantum computer.**TBD. See also:*Majorana-based quantum computer*.**Majorana quantum computing.**TBD. See also:*Majorana-based quantum computer*.**Majorana quasiparticle.**TBD. See also:*Majorana-based quantum computer*.**Majorana zero mode.**TBD. See also:*Majorana-based quantum computer*.**majorization.**TBD.**management.**Middle-level and senior-level leadership within an*organization*. Responsible for direction, strategy, decisions, budgeting, and hiring.**management approval.**The*process*of getting*management*to sign off on the*concept*of an*acquisition*of a*product*or*service*, after a*management review*. See also:*budget approval*.**management review.**The*process*of*management*studying and analyzing a proposal for the*acquisition*of a*product*or*service*, to be followed, if successful, by*management approval*. See also:*budget approval*.**mandatory requirement.**A*requirement*for a*system*which must be met, in contrast to an*optional requirement*which is preferred and encouraged, but not strictly mandatory.**manifestations of quantum theory.**TBD.**manufacturing process.**The*technology*and*processes*needed to*produce*a*system*,*product*,*component*, or*material*.**many-body localization.**TBD. Abbreviated as*MBL*.**many-body quantum systems.**TBD. Such as molecules.**map.**To perform a*mapping*. Alternatively, a*table*which*maps*or*transforms*from an*input value*to an*output value*.**mapping.**The process of*transforming*an*input value*to an*output value*. Similar to a*function*but the set of*input values*is very limited so that a simple*table*can perform the*transformation*rather than requiring*computation*and*code*. Alternatively, the*table*itself.**mark.**A visual indication of some significance, intended to indicate either a*location*, an*entity*, or some*meaning*, generally*symbolic*. Might be one or more*characters*, possibly even Greek, or some*graphical symbol*which is not a*character*. See also:*symbol*and*symbolic mark*.**mass.**The*quality*of an*object*which relates to the degree or extent to which it responds to*force*or*gravity*, in contrast to*photons*which have no*mass*and are unaffected by*force*and*gravity*. See also:*matter*and*massless*. Alternatively, simply a characterization of something as being large or plentiful, such as*mass storage*.**mass storage.***Memory*used to store*data*that either will not fit in*main memory*or which will be needed either by another*computer program*or by a*computer program**executing*at some future time. Generally capable of storing a very large amount of*data*, generally many times greater than that which will fit in*main memory*. For a*classical computer*, disk drives and tape drives were used for this purpose. In more recent years,*flash storage*(*solid-state drive*) has become more popular even though having a lesser capacity. At the present,*quantum computers*have no*mass storage*.**massless.**Having no*mass*.**matchcircuit.**TBD.**matchgate.**TBD.**material.**Quantities of*atoms*and*molecules*which can be assembled in forms which allow*objects*to be constructed. Roughly a synonym for*matter*, but with emphasis on being in a form which has utility, such as construction materials, rather than the purely abstract, occurring at too small a scale to have utility, or being in a non-*solid**state*(gas, liquid, or plasma.)**mathematical.**Having some connection to*mathematics*.**mathematical calculation.**The use of*mathematical operations*to*calculate*some*quantity*from given*values*. Shortened as*calculation*. See also:*formula*and*algebraic calculation*.**mathematical constant.**A*value*or a*symbolic name*for the*value*which has a conceptual significance in*mathematics*or a scientific field such as*physics*or*quantum mechanics*, such as*e*,*pi*,*i*, or*h*.**mathematical formula.**An expression of a*mathematical calculation*, using*values*and*mathematical operations*. See also:*mathematical function*.**mathematical framework.**A portion of*mathematics*which defines an*approach*to a modeling and working with a significant set of*problems*.**mathematical function.**A*mapping*of any number of*input values*to an*output value*, from a*domain*to a*range*. In a*programming language*the*mapping*is performed by*code*. See the Wikipediaarticle. See also:*Function (mathematics)**domain of a function*and*range of a function*.**mathematical matrix.**See*matrix*.**mathematical operation.**Any*operation*used in a*mathematical formula*, including addition, subtraction, multiplication, division, square root, exponential, and modulus or remainder, producing a*real value*,*complex value*or an*integer value*. The operands of a*mathematical operation*can be*values*,*variables*,*special values*such as*e*and*pi*,*functions*, or parenthesized*mathematical formulas*. See also:*mathematical formula*and*algebraic expression*.**mathematics.**The study, theory, concepts, and practice of*numbers*, shapes,*calculation*, structure, space,*symbols*, relationships, and*logic*, as distinct from the actual*real world*,*science*, and*applications*of those concepts. See the Wikipediaarticle.*Mathematics***matrix.**A*mathematical framework*used to represent*operators*in*quantum mechanics*. See the Wikipediaarticle. See also:*Matrix (mathematics)**column matrix*,*column vector*,*row matrix*,*row vector*,*bra*,*ket, unitary matrix*. Alternatively, any two-dimensional or*tabular*format of*model*or presentation of*data*or*information*.**matrix product state (MPS) tomography.**See*matrix product state tomography*.**matrix product state tomography.**TBD. See thepaper by Lanyon, Maier, et al. Abbreviated as*Efficient tomography of a quantum many-body system**MPS tomography*.**matter.***Physical bodies*,*material*, and*particles*which have*mass*, in contrast to*photons*which have no*mass*. May be in a*solid*, liquid, gas, or plasma state.**maximally entangled basis.**TBD.**maximally entangled state.**TBD.**maximally entangled two-qubit states.**TBD.**maximally entangling XX gate.**TBD.**maximum coherent depth.**The*quantum circuit depth*after which*quantum coherence*declines to an unacceptable degree. Approximately the ratio of the*coherence time T2*over the*gate time*.**MBL.**Initialism for*many-body localization*.**McWeeny purification.**TBD.**measurable quality.**A*quality*of a*system*which can be*measured*. See also:*observable quality*and*detectable quality*. See also:*measurable quantity*.**measurable quantity.**A*quantity*of a*system*which can be*measured*. See also:*observable quantity*and*detectable quantity*. See also:*measurable quality*.**measure.**An attempt to*observe*or measure the*quantum state*of a*quantum system*or*qubit*. See*measurement*. See also:*observe*,*final results*, and*collapse of wave function*.**measure of coherence.**TBD.**measurement.**See*quantum measurement*. Synonym for*readout*. See also:*intermediate measurement*.**measurement in the computational basis.**TBD. See also:*computational basis*.**measurement in the standard basis.**TBD.**measurement logic gate.**See*quantum measurement logic gate*.**measurement noise.**TBD.**measurement phase.**See*quantum measurement phase*.**measured state**. The*quantum state*of one or more*qubits*, as captured by*quantum measurement*.**the measurement problem.**The fact that the act of capturing the*quantum state*of a*qubit*via*measurement*returns only a single*real eigenvalue*of the*quantum state*and causes the*quantum state*of that*qubit*to*collapse*, causing the rest of the*quantum state*to be lost.**measurement results.**The collection of individual*results*or*measurements*of the*quantum states*of the*qubits*of interest upon completion of*execution*of a*quantum logic circuit*or*quantum program*. The*results*, collectively. May simply be referred to as the*measurements*.**mechanical.**Relating to*motion*and*mechanical force*.**mechanical force.**Any*force*which*causes*or results in a*motion*,*mechanical pressure,*or*mechanical stress*.**mechanical movement.**A change in the*position*of a*material*or*object*as the result of the application of*mechanical force*. Synonym for*motion*.**mechanical pressure.**A*detectable*or*measurable*degree of*mechanical force*on a*material*. Commonly compression.**mechanical stress.**See*mechanical pressure*. May be compression, tension, or shear. May lead to*mechanical strain*.**mechanical strain.**A*detectable*or*measurable*degree of compression, expansion, or deformation of a*material*due to*mechanical stress*.**mechanical wave.**A*wave*propagated through a*medium*(*solid*,*liquid*,*gaseous*, or*plasma*, but not a*vacuum*) as a*result*of*mechanical pressure*. See also:*sound*.**mechanics.**The branch of*physics*concerned with motion and behavior of*physical bodies*under the influence of forces and interactions with other*physical bodies*. Subfields include*classical mechanics*(*Newtonian mechanics*),*quantum mechanics*, and*statistical mechanics*(e.g., thermodynamics.) See the Wikipediaarticle.*Mechanics***medium.**Any*material*or*state of matter*capable of*transmitting*either*matter*or*energy*, including*heat*,*sound*, and*electromagnetic radiation*. See also:*solid medium*,*liquid medium*,*gaseous medium*, or*plasma medium*. [TBD: does a vacuum constitute a medium even though it has no matter, but can transmit both matter and energy?].**medium-sized quantum computer.**Vague definition of the usability of a*quantum computer*in terms of its*qubit count*. Currently, 20*qubits*would be considered a*medium-sized quantum computer*. Less than that would be a*modest-sized quantum computer*or a*small-sized quantum computer*. Currently, 50 or more qubits would be considered a*large-sized quantum computer*. Different individuals and organizations might quibble over these numbers and characterizations. These numbers will rise each year as more*qubits*become available. In two years, 50 to 100*qubits*will likely be considered a*medium-sized quantum computer*and 128, 192, or 256*qubits*would be considered a*large-sized quantum computer*. In five years, the number for medium-sized might be 512, 1024, 2048, 4096, or even 8192, depending on the pace of*hardware*advances.**member.**Belong to a*group*.**membership.**See*member*.**memory.***Storage*for*data*which can be accessed very rapidly, in contrast to*mass storage*. Generally a synonym for*main memory*, although*classical computers*have a variety of forms of*memory*.**message.**Any amount of*information*which is to be transmitted between two locations — from a*sender*to a*recipient*, which may be*people*or*processes*(*computer programs*.) It may consist of readable,*natural language text*, such as an email or social media message, or arbitrary technical symbols,*raw data*, or*binary data*, including*executable programs*. See also:*cryptographic message*and*interprocess communication***method.**Generally a synonym for*algorithm*. May be a rather informal process, while an*algorithm*will generally be rather formal. Generally, a*process*for achieving a*goal*.**millikelvin.**One-thousandth (1/1,000) of a degree*kelvin*(*K*). Ultra-cold temperature only a small fraction of a single degree above*absolute zero*. See the Wikipediaarticle. Abbreviated as*Orders of magnitude (temperature)**mK*.**microcode.**See*firmware*. Specialized*code*within a*processor*which is used to implement some or all of the*functions*or*instructions*of the*processor*.**microwave.**High*frequency*short*wavelength**radio waves*(*electromagnetic radiation*) which travel in a straight line. Higher*frequency*than normal*radio waves*and lower frequency than*visible light*or*infrared*. In the context of*quantum computing*they can be used to control*qubits*. See the Wikipediaarticle. See also:*Microwave**microwave circulator*,*microwave pulse*, and*microwave signal*.**microwave circulator.**A*device*for controlling the flow of a*microwave signal*. See the Wikipediaarticle. In a*Circulator**quantum computer*this is referred to as a*quantum circulator*. See the Physicsarticle (synopsys.)*Synopsis: Quantum Circulators Simplified**Microwaves*are used to control*qubits*, so careful control of the flow of*microwaves*is needed to minimize*quantum decoherence*.**microwave drive.**TBD. Use of*microwaves*to control a*qubit*, commonly with a*resonator*, such as for*execution*of a*quantum logic gate*. See also:*resonator port*and*flux bias line*. Referenced indoc from Rigetti Computing.*The Quantum Processing Unit (QPU)***microwave pulse.**A*microwave signal*of very short duration. Technique for controlling or manipulating the*quantum state*of a*quantum system*(even a single*qubit*) using an external*microwave*source. See also:*coherent control*. See the.*IBM Q FAQ***microwave signal.**See*microwave*or*microwave pulse*.**middleware.**See*middleware software*.**middleware software.***Software libraries*,*software frameworks*, and*software services*which provide a foundation for*development*of*application software*. This includes*database software*. It is positioned in the middle, between the*operating system*and*application software*.**minimal quantum latency.**TBD.**minimally connected.**See*minimally entangled.***minimally entangled.**Only at most a few possible pairs of*qubits*of a*quantum computer*may be*entangled*simultaneously, in contrast to*fully entangled*, where all possible pairs of*qubits*may be*entangled*,*highly entangled*where most pairs of*qubits*are*entangled*, or*partially entangled*, where more than a few but not all possible pairs of qubits may be*entangled*at the same time.**mitigate.**See*mitigation*.**mitigation.***Capability*of modifying*conditions*to counteract some*event*or*conditions*which have been*detected*, to make it appear as if they hadn’t occurred. Such as*errors*—*error detection*and*error correction*. See also:*detection*and*compensation*.**mitigation of errors.**See*quantum error correction*. See also:*mitigation*.**mixed state.**A*quantum state*which is a*superposition*of the two*basis states*, |0> and |1>. This reduces the*amplitude*(*probability amplitude*) of each of the*complex vectors*representing the*basis states*, such that the squares of the*modulus*(*magnitude*) for each*amplitude*sum to 1.0 as required for unitarity. Since the*modulus*for each*complex vector*is no longer 1.0, the*complex vectors*are inside of the*Bloch sphere*rather than on its surface. In contrast to*pure state*which is either a*basis state*or a rotation of a*basis state*, so that the*modulus*of the*amplitude*of the*basis vector*is 1.0, putting it on the surface of the*Bloch sphere*, rather than on the interior as for a*mixed state*. [TBD: verify] See the Wikipediaarticle.*Quantum state***mixed state entanglement.**TBD.**mK.**Initialism for*millikelvin*.**modest-sized quantum computer.**Vague term which could refer to a*quantum computer*which: 1) has a relatively small number of*qubits*, 2) has more than a relatively small number of*qubits*, 3) has more than a few*qubits*but not a lot of*qubits*, a dozen of so, in the range of 8 to 16, or 4) is relatively small in size, closer to a smartphone or desktop computer, or at least no bigger than a filing cabinet, compared to room-size*quantum computers*of 2018. See also:*small-sized quantum computer*,*medium-sized quantum computer*, and*large-sized quantum computer*..**mod function.**See*modulo operation*.**modular exponentiation.**TBD.**modular multiplication.**TBD. Referenced in thepaper by Beauregard.*Circuit for Shor’s algorithm using 2n+3 qubits***modulo operation.**The remainder after performing an*integer*division between two*numbers*(*integer*or*real*.) See the Wikipediaarticle.*Modulo operation***modulus.**See*absolute value*. Alternatively, the*modulo operation*for*integer*and*real numbers*.**molecule.**Two or more*atoms*which have formed one or more*chemical bonds*which cause them to persist in close physical proximity and to act as an integrated unit. The*atoms*may or may not be of the same*element*.**Mølmer-Sørensen gate.**TBD.**Molmer-Sorensen gate.**See*Mølmer-Sørensen gate*.**Mølmer-Sørenson interaction.**TBD.**Molmer-Sorensen interaction.**See*Mølmer-Sørensen interaction*.**Mølmer-Sørensen XX entangling gate.**TBD.**Molmer-Sorensen XX entangling gate.**See*Mølmer-Sørensen XX entangling gate*.**Mølmer-Sørensen XX gate.**TBD.**Molmer-Sorensen XX gate.**See*Mølmer-Sørensen XX gate*.**moment of time.**A particular point in*time*. May be either a*discrete moment of time*or part of a*continuous period of time*.**moments of time.**Two or more discrete points in*time*, or all of the*moments*during some*continuous period of time*.**momentum.**See*linear momentum*.**monogamy of entanglement.**TBD.**Moore’s Law.**Proposition that the density of*transistors*on an*integrated circuit*will double every two years. May now have slowed down to doubling every two and a half to three years. A continued deceleration is a negative for*classical computers*and an argument in favor of*quantum computing*. See the Wikipediaarticle. See also:*Moore’s Law**post-Moore’s Law era*.**motion.***Mechanical movement*. See also:*mechanical force*.**motional modes of the linear ion chain.**TBD. relevant to a*trapped-ion quantum computer*.**MPS.**Initialism for*matrix product state*. See also:*MPS tomography*and*matrix product state tomography*.**MPS tomography.**Abbreviation for*matrix product state tomography*.**multi-byte character code.**For*character codes*in*Unicode*which do not fit in a single*8-bit byte*,*Unicode*defines several methods for representing those larger values as multiple*bytes*, most notably*UTF and UTF-8*. See the Wikipediaarticle, specificialy the*Unicode*section. See also:*Unicode Transformation Format and Universal Coded Character Set**UTF-8*,*UTF-16*and*UTF-32*.**multi-degree-of-freedom multiplexed solid-state quantum memory.**TBD. Referenced in thearticle. Shortened as*Researchers achieve multifunctional solid-state quantum memory**multiple-DOF memory*.**multipartite entanglement.***Quantum entanglement*of of three or more*qubits*, in contrast to*bipartite entanglement*which is limited to only a*pair of qubits*. Alternatively, the*quality*of a*quantum computer*of supporting*entanglement*of three or more*qubits*in a particular*entanglement*at a time. Although*multipartite entanglement*does cover the case of exactly three*qubits*in a single*entanglement*, the term*tripartite entanglement*refers specifically to the case of*entanglement*of exactly three*qubits*. At present, here in August 2018,*current quantum computers*support only*bipartite entanglement*, no more than*pairs of qubits*. [TBD: Whether or to what extent*simulators*support multipartite entanglement].*Quantum communication*has a more pressing need for*multipartite entanglement*. See the Wikipediaarticle and the*Multipartite entanglement*paper by Qu, Dong, Wang, Bao, Song, and Song. see also:*Bipartite entanglement in AJL’s algorithm for three-strand braids**bipartite entanglement*and*tripartite entanglement*.**multiple-DOF memory.**Short for*multi-degree-of-freedom multiplexed solid-state quantum memory*.**multiple-DOF memory with high multimode capacity.**TBD. Referenced in thearticle. See*Researchers achieve multifunctional solid-state quantum memory**multi-degree-of-freedom multiplexed solid-state quantum memory*.**multiple inheritance.**In*object-oriented programming*(*OOP*), an*OOP class*can be*derived*from more than one*parent class*, meaning that it*inherits*access to the*data items*and*functions*of all of its*parent classes*.**multiplexed quantum repeater.**TBD. Referenced in thearticle.*Researchers achieve multifunctional solid-state quantum memory***multiprocessor.**See*multiprocessor computer system*.**multiprocessor computer system.**A*computer system*with more than one*processor*. This can be any combination of*secondary processors*and*parallel processors*. Generally, it’s not the*secondary processors*(such as*coprocessors*or*GPUs*) which make it a*multiprocessor system*, but the*parallel processors*, each of which is capable of*executing*a full*program*for a*user*, in contrast to the*specialized software*which*executes*on a*secondary processor*. See also:*main processor*,*coprocessor*,*adjunct processor*,*auxiliary processor*,*secondary processor*,*parallel processor*, or*graphics processor*.**multiprocessor system.**See*multiprocessor computer system*.**multistate, contracted variational quantum eigensolver.**TBD. Abbreviated as*multistate, contracted VQE*or*MC-VQE*.**multistate, contracted VQE.**Abbreviation for*multistate, contracted variational quantum eigensolver*.**mutually orthogonal entangled states.**TBD.**n.**Generally the count of*values*in some set or collection of*values*or*data structure*.**n-bit value.**Any*value*on a*classical computer*which is represented as*n*contiguous*bits*, which can represent only a single*value*out of a range of 2 to the*n*distinct*values*, in contrast to an*n-qubit quantum value*, which can represent any or all 2 to the*n**values*simultaneously.**n-qubit Clifford operation.**A*Clifford operation*which operates on*n**qubits*. A sequence of one or more*quantum logic gates*operating on*n**qubits*whose effect on the*quantum state*of those*qubits*can be expressed as a sequence of*Clifford gates*. TBD. Referenced in thepaper by Jozsa and Van den Nest.*Classical simulation complexity of extended Clifford circuits***n-qubit quantum register.**A*sequence*of*n**qubits*considered as a single*unit*. Comparable to a*register*of a*classical computer*. Or, comparable to an*n-bit value*of a*classical computer*. Except that an*n-qubit quantum register*can hold 2 to the*n**quantum states*simultaneously.**n-qubit value.**See*n-qubit quantum value*.**n-qubit quantum value.**The collection of*values*represented in a collection of*n**qubits*, which can be any number of*values*up to and including 2 to the*n**values*, using*quantum superposition*, in contrast to an*n-bit value*of a*classical computer*which can represent only a single*value*out of 2 to the*n*possible*values*.**N-representability.**TBD.**N-representability conditions.**TBD.**N-representable manifold.**TBD.**name.**See*identifier*and*label*, in contrast to a*word*from a dictionary, a*number*, or a*symbol*. Technically, a*name*could be a*word*or a*number*, or possibly even a*symbol*, but it would*function*as an*identifier*of*label*rather than have the usual*meaning*of a*word*,*number*, or*symbol*. May be a*proper name*.**narrow-band quantum Fourier transform.**A*banded quantum Fourier transform*where the m or b*bandwidth*parameter is relatively small compared to the total number of bits in the input number, commonly 8 qubits. Transform entries which are very small will be discarded since they will have very little impact on the final results but consume a lot of computational resources. In contrast to a*full quantum Fourier transform*.**narrow-purpose.**See*narrow purpose*.**narrow purpose.**Suitable only for a relatively narrow range of uses, limiting*application*, in contrast to the even narrower range of use of*fixed purpose*, or the wide range of uses of*general purpose*.**nascent technology.**A*technology*which is relatively new and unproven.**National Quantum Coordination Office.**TBD. Referenced inbill.*National Quantum Initiative Act***National Quantum Initiative.**A proposal in 2018 for the U.S. government to fund research in*quantum information science*for ten years. Seepress release and text of*SST Committee Approves the National Quantum Initiative Act*bill.*National Quantum Initiative Act***National Quantum Initiative Act.**See*National Quantum Initiative*and text ofbill.*National Quantum Initiative Act***National Quantum Initiative Advisory Committee.**See*National Quantum Initiative*. Referenced inbill.*National Quantum Initiative Act***National Quantum Initiative Program.**See*National Quantum Initiative*. Referenced inbill.*National Quantum Initiative Act***natural language.**A*language*used by people, homo sapiens. Both spoken and written.**natural language word.**A representation of a*word*from a*natural language*as*text*, simply the literal*characters*.**natural language text.***Text*which is a sequence of*natural language words*and*punctuation*rather than simply a raw*sequence of characters*.**nanoscale thermodynamics.**TBD.**near-term device.**See*near-term quantum computer*. Technically, a*device*could be any type of*computer*, including a*classical computer*, but in the context of*quantum computing*it is safe to presume that it is a reference to a*quantum computer*, but it could also be a reference to a single*qubit*, or a*chip*within a*quantum computer*.**near-term intermediate scale quantum.**See*near-term intermediate-scale quantum*.**near-term intermediate-scale quantum.**See*near-term intermediate-scale quantum computer*.**near-term intermediate scale quantum computer.**See*near-term intermediate-scale quantum computer*.**near-term intermediate scale quantum computer.**See*near-term intermediate-scale quantum computer*.**near-term intermediate-scale quantum computer.**See*noisy intermediate-scale quantum computer*.**near-term intermediate scale quantum device.**See*near-term intermediate-scale quantum device*.**near-term intermediate-scale quantum device.**See*noisy intermediate-scale quantum device*.**near-term quantum computer.***Quantum computer designs*for which*quantum computers*are available today, off the shelf, for actual use by real*developers*. Commonly a reference to*near-term intermediate-scale quantum computer*or*noisy intermediate-scale quantum computer*. Alternatively, limited to*commercial availability*, excluding*machines*which are only operating in research labs. Alternatively, includes*machines*which are operating in research labs. Alternatively, includes*designs*which are expected to be built in the near term, the next few months to a year or so. But excludes*designs*which are not expected to be built for more than a year or so. See also:*current quantum computer*and*future quantum computer*.**near-term quantum device.**See*near-term quantum computer*.**near-term quantum processor.**See*near-term quantum computer*.**nearest-neighbor matchgate.**TBD.**neighboring qubits.***Qubits*which are capable of being*coupled*(*entangled*). This typically means that they are physically adjacent on a*quantum chip*, but that is not an absolute requirement. The key requirement is that there be an*interconnection*between the*qubits*, such as a*resonator*which permits*coupling*to be initiated.**net charge.**See*net electric charge*.**net electric charge.**The exact degree of imbalance between the number of*protons*and the number of*electrons*of an*ion*or*charged particle*. The number of*protons*minus the number of*electrons*. +1 means a deficit of one*electron*. -2 means a surplus of two*electrons*. See also*balance of charge.***net negative charge.**The quality of an*ion*or*charged particle*having a net surplus of electrons — more*electrons*than*protons*. The exact number of the surplus of*electrons*. See also:*net electric charge.***net positive charge.**The quality of an*ion*or*charged particle*having a net deficit of electrons — fewer*electrons*than*protons*. The exact number of the deficit of*electrons*. See also:*net electric charge.***network.**Two or more*computer systems*which are*connected*. Also known as*nodes*. The*connection*may be physical, such as with*cabling*,*wirelessly*, or over a*communication network*. They may be in relatively close proximity, a*local area network*, or be widely dispersed, a*wide area network*. Whether near or far, the systems can constitute the*Internet*if they use standard*Internet protocols*for*communication*. Alternatively, synonym for a*graph*in*graph theory*.**networking quantum computers.**See*quantum network*.**neural network.**TBD. See the Wikipediaand*Neural network*articles. See also:*Artificial neural network**quantum neural network (QNN)*and*artificial intelligence*.**Newtonian mechanics.**The subfield of*physics*,*mechanics*, associated with the motion and interactions of macroscopic*physical bodies*, larger than*atoms*but traveling much slower than the speed of light. The world of everyday*objects*, machinery, vehicles, billiard balls, planets, moons, satellites, stars, and galaxies. In contrast to*quantum mechanics*, which is associated with motion and interactions at the*atomic*and*subatomic*level, where the distinction between*particles*and*waves*overlaps and is more about*probability*than*certainty*and*determinism*. Synonym for*classical mechanics*.**next quantum revolution.**Vague hyperbole for any upcoming major advances in the field of*quantum computing*. See the NSFweb page. See also:*The Quantum Leap: Leading the Next Quantum Revolution**quantum revolution*.**nibble**. On a*classical computer*, may be interpreted either as a*4-bit integer*or as simply four*bits*. Alternatively half a byte. Alternatively a*hexadecimal digit*.**niche application.**An*application*category which is relatively narrow and specialized. Alternatively, any*application*, in the sense that that is what*applications*are all about — each of them focuses on a particular niche, in contrast to being truly*general-purpose*.**niobium.**A metallic*element*which becomes a*superconductor*below 9.2 K. Used to create a*superconducting loop*which in conjunction with a*Josephson junction*is used to construct a*qubit*, such as a*superconducting transmon qubit*. See the Wikipediaarticle.*Niobium***NISQ.**Initialism for*noisy intermediate-scale quantum*or*noisy intermediate-scale quantum device*. Refers to*noisy intermediate scale quantum computer*. Some interpret it as*noisy intermediate stage quantum*— scale vs. stage. Alternatively, initialism for*near-term intermediate-scale quantum*,*near-term intermediate-scale quantum computer*, or*near-term intermediate-scale quantum device*.*Current quantum computers*and*near-term quantum computers*which have a moderate number of*qubits*(10 to 128 or so) supporting a moderate*circuit depth*of*quantum logic gates*(20 to 100 or so) which are fairly reliable but not*fault-tolerant*per se.**NISQ algorithm.***Algorithm*which has been*designed*and*optimized*to exploit*noisy intermediate scale quantum computers*(*NISQ computer*or*NISQ*for short) —*current quantum computers*and*near-term quantum computers*, which have a moderate number of*qubits*(50 to 100) supporting a moderate*circuit depth*of*quantum logic gates*(40 to 50 or so) which are fairly reliable but not*fault-tolerant*per se.**NISQ chemistry.**TBD.**NISQ chemistry computation.**TBD.**NISQ computer.**See*noisy intermediate scale quantum computer*.*Quantum computer*based on*noisy intermediate scale quantum technology*.**NISQ device.**Short for*noisy intermediate-scale quantum device*. Generally*NISQ computer*.**NISQ era.**The*stage*of the*quantum computing market*when*NISQ computers*are common. The stage that we are on the verge of entering, as of July 2018.**nitrogen-vacancy center.**Exploiting the*physics*of defects in diamonds for construction of*qubits*. Also referred to as*diamond vacancy*. See the Wikipediaarticle.*Nitrogen-vacancy center***NMR.**Initialism for*nuclear magnetic resonance*.**NMR quantum computer.**See*nuclear magnetic resonance quantum computer*.**no-cloning theorem.**A*quantum circuit*or*quantum algorithm*cannot make an exact copy of the full*quantum state*of another*qubit*, since that would be comparable to*measuring*the*qubit*which would cause its*wave function*to*collapse*. Instead,*quantum algorithms*utilize*quantum entanglement*, such as with the*controlled-NOT gate*. See the Wikipediaarticle.*No-cloning theorem***no net charge.**An*atom*with a*balance of charge*— the count of*protons*is the same as the count of*electrons*. The quality of an*insulator*.**node.**A representation of*data*in a*graph*, in*graph theory*. Alternatively, a*computer system*in a*network*. A*network*is a*graph*.**noise.**See*quantum noise*.**noise model.***Parameters*for*simulated noise*so that a*quantum simulator*can produce*results*more closely aligned with those of a*real quantum computer*. Otherwise, a*quantum simulation*executed on a*classical computer*would tend to be*deterministic*rather than*probabilistic*. The*noise model*needs to be tuned to reflect the behavior of a particular*design*of*quantum computer*and*architecture*.**noisy.***Execution*of*quantum logic gates*is prone to*quantum errors*due to either*quantum decoherence*or*environmental factors*.**noisy intermediate-scale quantum.**See*noisy intermediate scale quantum technology*. Abbreviated as*NISQ*.**noisy intermediate scale quantum computer.**See*noisy intermediate-scale quantum computer*.**noisy intermediate-scale quantum computer.***Quantum computer*based on*noisy intermediate scale quantum technology*. Shortened as*NISQ computer*.**noisy intermediate scale quantum device.**See*noisy intermediate-scale quantum device*.**noisy intermediate-scale quantum device.**Generally a*noisy intermediate-scale quantum computer*. Abbreviated as*NISQ device*or simply*NISQ*.**noisy intermediate scale quantum technology.**See*noisy intermediate-scale quantum technology*.**noisy intermediate-scale quantum technology.***Quantum circuits*with an intermediate number of*qubits*(10 to 128 or so) and an intermediate*circuit depth*of*quantum logic gates*(10 to 100 or so) will be somewhat*noisy*but not so noisy that the*results*are completely unusable, and will be reasonably satisfactory for some*applications*. Smaller*circuits*may not encounter significant*quantum errors*, and larger*circuits*may encounter too many*quantum errors*for the*results*to be usable See thepaper by John Preskill. Abbreviated as*Quantum Computing in the NISQ era and beyond**NISQ*. See also:*NISQ computer*and*noisy intermediate scale quantum computer*.**noisy intermediate stage quantum.**See*noisy intermediate-scale quantum*.**noisy physical gate.**A*quantum logic gate*applied to a*quantum physical qubit*which causes a*quantum error*, even if*quantum error correction*(*QEC*) is able to correct the*error*using other*quantum physical qubits*, which collectively comprise a*quantum logical qubit*. See thepaper by Abu-Nada, Fortescue, and Byrd.*Optimizing the Frequency of Quantum Error Correction using the [[7,1,3]] Steane Code***noisy quantum computer.**A*quantum computer*constructed with*noisy qubits*— they do not have*quantum error correction*(*QEC*), so that they are prone to a non-trivial*quantum error rate*.**noisy quantum device.**See*noisy quantum computer*. Alternatively, a*noisy qubit*.**noisy quantum hardware.**TBD.**noisy qubit.**A*qubit*which is*noisy*— it does not have*quantum error correction*(*QEC*), so that it is prone to a non-trivial*quantum error rate*.**non-adiabaticity.**TBD.**non-adaptive Clifford circuit.**A*Clifford circuit*in which*operations*are fixed and will not vary in response to any*intermediate measurements*, in contrast to a*non-adaptive Clifford circuit*in which the*operations*may be chosen based on*intermediate measurements*of the*outcomes*of previous*operations*. TBD. Referenced in thepaper by Jozsa and Van den Nest.*Classical simulation complexity of extended Clifford circuits***non-clifford gate.**A*quantum logic gate*whose effect on the*quantum state*of a*qubit*cannot be expressed as a sequence of*basic Clifford gates*. TBD. Referenced in thepaper by Jozsa and Van den Nest.*Classical simulation complexity of extended Clifford circuits***non-clifford operation.**A sequence of one or more*quantum logic gates*whose effect on the*quantum state*of a*qubit*cannot be expressed as a sequence of*basic Clifford gates*. TBD. Referenced in thepaper by Jozsa and Van den Nest.*Classical simulation complexity of extended Clifford circuits***non-computable function.**TBD. In contrast to a*computable function*.**non-executable statement.**A*statement*in a*high-level programming language*which will not perform any action when the program is*executing*, such as a*declaration*, in contrast to an*executable statement*. It is possible that a*non-executable statement*could cause some action, such as*evaluating an expression*to*initialize*a*variable*.**non-nearest-neighbor matchgate.**TBD.**non-numeric.**See*non-numeric value*.**non-numeric value.***Data*which is not in the form of a numeric value —*real number*,*complex number*, or*integer number*. This can include*boolean values*,*characters*,*text*or*strings*,*composite values*such as pairs or lists of values, or*user-defined values*. Whether a*rational number*, expressed by a*numerator*and*denominator*which are*integers*should be considered a*numeric value*or a*non-numeric value*is unclear and debatable — it works both ways.**non-numeric data.**See*non-numeric value*.**non-planar quantum integrated circuit.***Quantum integrated circuit*based on a*non-planar quantum integrated circuit architecture*.**non-planar quantum integrated circuit architecture.**An*architecture*for*quantum integrated circuits*utilizing three-dimensional*cavities*for*resonators*. See thepaper by O’Brien, Vahidpour, Whyland, Angeles, Marshall, Scarabelli, Crossman, Yadav, Mohan, Bui, Rawat, Renzas, Vodrahalli, Bestwick, and Rigetti.*Superconducting Caps for Quantum Integrated Circuits***non-quantum hardware.***Hardware*whose function is focused on processing of*digital signals*or*analog signals*, in contrast to*quantum hardware*whose function is focused on processing of*quantum states*. The*hardware of a quantum computer*outside of the*qubits*, including*quantum control*.**non-real.**A*number*which is not a*real number*. An*imaginary number*. The*imaginary*part of a*complex number*. Alternatively, a*non-numeric*.**nonadiabatic and non-abelian holonomic quantum gates.**TBD. Referenced in thepaper by Nagata, Kuramitani, Sekiguchi, and Kosaka.*Universal holonomic quantum gates over geometric spin qubits with polarised microwaves***nondeterministic.**A*system*,*process*,*algorithm*, or*code*which is*not*governed by*determinism*— the starting conditions*do not*completely determine the*final results*. In contrast to*deterministic*.**nondeterministic polynomial time.**TBD. Abbreviated as*NP*. See also:*polynomial time*.**nondeterministic result.**The*uncertainty*and*probabilistic*nature of*results*on a*quantum computer*which tends to make them at least somewhat*nondeterministic*, in contrast to the*certainty*and*deterministic*nature of*results*on a*classical computer*. See also:*deterministic result*.**nonlocal property.**See*quantum nonlocality*.**nonlocality.**See*quantum nonlocality*.**nontrivial circuit.**A*quantum logic circuit*with more than simply a very few*quantum logic gates*. See also:*trivial circuit*.**NP.**Initialism for*nondeterministic polynomial time*. See also:*P*.**nuclear magnetic resonance.**Shortened as*NMR*.**nuclear magnetic resonance quantum computer.**A*quantum computer*which utilizes*molecules*for*qubits*, using*nuclear magnetic resonance (NMR)*to control the*spin state*of*atoms*in the*molecule*. See the Wikipediaarticle. See the*Nuclear magnetic resonance quantum computer*paper by J. A. Jones.*Quantum Computing and Nuclear Magnetic Resonance***number.***A symbol*for a*value*(*numeric value*) which is a count, measure, or simply a label. See the Wikipediaarticle. The*Number**meaning*is clear on a*classical computer*, but not so clear on a*quantum computer*, which has only*quantum states*, such that*measuring*a*qubit*will return a binary 0 or 1.**numeric.**The quality of*numbers*and*numeric values*, including absolute*numbers*and differences or distances between*numbers*. Alternatively,*text*or a*character string*which is in fact a*representation*of a*number*. See*numeric value*.**numeric value.**A*real value*,*complex value*, or*integer value*. See also:*non-numeric value*and*rational number*.**numerical.**See*numeric*.**numerical calculation.**See*numerical computation*.**numerical computation.***Computation*with*algebraic calculations*with an emphasis on obtaining*numerical results*.**numerical gradient.**TBD. In contrast to an*analytical gradient*.**numerical results.**The*results*of*numerical computation*which produce some set of*real values*,*complex values*, and*integer values*.**OAM.**Initialism for*orbital angular momentum*.**OAM states.**Short for*orbital-angular-momentum states*.**object.**A localized thing,*hardware*,*physical system*,*software*, or*data*, which might be referenced, acted upon, or act on other*objects*. It may or may not have a*type*. It may or may not have a*name*. See also:*entity*. Alternatively, the basic unit of*structured information*in the*object-oriented programming*(*OOP*) paradigm of*design*and*coding*.**objective.**Synonym for*goal*. Alternatively, the*objective value*for an*objective function*for given*input values*.**objective function.**A*mathematical function*which an*algorithm*seeks to minimize, maximize, or otherwise optimize. See*quantum annealing*. See the Wikipediaarticle and the D-Wave*Mathematical optimization*whitepaper. See also:*Programming with D-Wave: Map Coloring Problem**objective value*and*objective*.**objective value.***Value*of the*objective function*for given*input values*. Shortened as*objective*.**object-oriented programming**. A paradigm or approach to organizing*code*and*data structures*based on the definition of a*hierarchy of classes*of*objects*, each of which has a well-defined set of*functions*which operate only on*objects*of that*class*or its*subclasses*. Abbreviated as*OOP*. No obvious way that this would fit into the*quantum world*at this time. But the question remains how*algorithms*and*code*based on the OOP paradigm can be migrated to the*quantum world*. See the Wikipediaarticle. See also:*Object-oriented programming**OOP object*and*OOP class*.**oblivious amplitude amplification.**TBD.**observe.**Same as*measure*. An attempt to observe or measure the*quantum state*of a*quantum system*or*qubit*. See*measurement*. See also:*final results*. See also:*collapse of wave function*.**observable.**A physical*quantity*of a system which can be*observed*or*measured*, such as the two*quantum states*of a*qubit*. In*quantum mechanics*an*observable*is an*operator*, which yields a*basis state*corresponding to an*eigenvector*based on the*probability*that the*quantum system*is in that*quantum state*, a*basis state*, which is a*basis vector*. The*probability*is the square of the*modulus*of the*eigenvalue*associated with that*eigenvector*. The*eigenvalue*is a*complex number*representing the*amplitude*(*probability amplitude*) for that*eigenvector*. The*basis states*for*current quantum computers*are |0> and |1>. Each*qubit*will have those two*basis states*as*observables*and their associated*eigenvectors*and associated*eigenvalues*. The*wave function*for a*quantum system*is the sum or*linear combination*of all of the*eigenvectors*of the*observables*and their*eigenvalues*. That*linear combination*permits*superposition*of more than one*eigenvector*(*basis state*.)*Current quantum computers*commonly have a pair of*observables*for each*qubit*, which are the two*spin states*. See the Wikipediaarticle. See also:*Observable**quantum operator*.**observable and measurable quality.**A*quality*of a*system*which can be*observed*and*measured*. See also:*observable quality*,*measurable quality*and*detectable quality*. See also:*observable and measurable quantity*and*observable or measurable quantity*.**observable and measurable quantity.**A*quantity*of a*system*which can be*observed*and*measured*. See also:*observable quantity*,*measurable quantity*and*detectable quantity*. See also:*observable and measurable quality*and*observable or measurable quantity*.**observable or measurable quality.**A*quality*of a*system*which can be*observed*or*measured*. See also:*observable quality*,*measurable quality*and*detectable quality*. See also:*observable and measurable quantity*and*observable and measurable quality*.**observable or measurable quantity.**A*quantity*of a*system*which can be*observed*or*measured*. See also:*observable quantity*,*measurable quantity*and*detectable quantity*. See also:*observable and measurable quality*and*observable and measurable quantity*.**observable quality.**A*quality*of a*system*which can be*observed*. See also:*measurable quality*and*detectable quality*. See also:*observable quantity*.**observable quantity.**A*quantity*of a*system*which can be*observed*. See also:*measurable quantity*and*detectable quantity*. See also:*observable quality*.**observation.**See*observe*.**on-chip quantum photonic processor.**A*quantum photonic processor*completely contained on a single*integrated circuit*, including the*qubit*itself.**one-dimensional Fermi-Hubbard model.**TBD. Abbreviated*1D FHM.***one-particle reduced density matrix.**TBD. Abbreviated as*1-RDM*.**one-qubit gate.**See*one-qubit quantum logic gate*. Abbreviated as*1Q gate*or*1Q*. Synonym for*single-qubit gate*.**one-qubit logic gate.**See*one-qubit quantum logic gate*. Abbreviated as*1Q gate*or*1Q*. Synonym for*single-qubit logic gate*.**one-qubit quantum logic gate.**A*quantum logic gate*which operates on only a single*qubit*. Abbreviated as*1Q gate*or*1Q*. Synonym for*single-qubit gate*,*one-qubit logic gate*, and*one-qubit gate*. See also:*two-qubit quantum logic gate*.**one state.**The*quantum state*of a*qubit*is |1>, equivalent to a binary value of 1, in contrast to the*zero state*, which is equivalent to a binary value of 0. Note that a*qubit*can be in*both*the*zero state*and*one state*at the same time due to*superposition*.**ongoing evolution of quantum computing.**Progress is being made on every front of*quantum computing*on a fairly frequent basis, including theory, foundation technology, research, hardware technology, system construction, commercial offerings, software tools, applications, and adoption for use.**OOP.**Initialism for*object-oriented programming*.**OOP class.**The definition of a*class*for a type of*object*according to the*object-oriented programming*(*OOP*) paradigm by which each*object*in the*class*has a defined set of*data items*as well as a defined set of*functions*which operate on those*data items*. A*hierarchy of classes*may be defined such that*subclasses*of a*class*may use*data items*and*functions*of both that*parent class*and any of its*superclasses*. See the Wikipediaarticle.*Object-oriented programming***OOP object.**An*object*of a*class*in*object-oriented programming*. See also:*OOP class*.**OpenQASM.**Short name for*Open Quantum Assembly Language*. Alternatively,*OPENQASM*.**Open Quantum Assembly Language.**A*quantum assembly language*offered as part of the IBM Q Experience. See thepaper. See the IBM QISKit OPENQASM web page. See the*Open Quantum Assembly Language*Github repository for both*QISKit/openqasm**code*and*specifications*.**open quantum system.**TBD. See the Wikipediaarticle. See also:*Open quantum system**quantum bath*.**operand.**An*argument*for an*operator*or*function*. In a*high-level programming language*this can be a*data value*or an*algebraic expression*.**operate beyond the supremacy regime.**TBD.**operating system.**Special*software*on a*computer system*which is responsible for managing*system*resources and scheduling*processes*for*execution*.*Application software*typically requires some significant degree of*middleware software*and*software tools*rather than running directly on the bare*operating system*. This concept is primarily for*classical computers*, including the*classical computer*which directly controls a*quantum computer*, but the*quantum computer*itself has no built-in*software*and certainly no*operating system*, just raw*hardware*. See also:*system software*and*system utilities*.**operation.**See*quantum logic operation*. In*classic computing*, an*operator*and its*operands*or*arguments*. Alternatively, the activity and functioning of a*system*,*device*,*computer*, or*organization*.**operational connection.**TBD.**operational resource.**TBD.**operational quantum hardware.**An*existing quantum computer*, in contrast to a*future quantum computer*. A*quantum computer*which has actually been built, in contrast to a*quantum computer*which is planned or only theorized.**operator.**In*classical computation*, an*operator*is a*function*of one or more*operands*, such as the plus*operator*(+) which adds two*numbers*. In*quantum mechanics*, an*operator*corresponds to an*observable*— see*observable*and*quantum operator*.**opinionated quantum instruction language.**Term used by Rigetti Computing for their*Quantum Instruction Language*(*Quil*) to indicate their expectation that the near-term usage of*quantum computers*will be as a*coprocessor*for a*classical computer*. Referenced indoc from Rigetti Computing.*The Quantum Virtual Machine (QVM)***opportunity.**A*situation*which can be exploited to attain a more advantageous*situation*by applying a*solution*. See also*problem*.**optical.**Relating to*visible light*. May or may not include*infrared light*and*ultraviolet light*.**optical crosstalk.**TBD.**optical fiber.**See*optical fiber cable*.**optical fiber cable.**A*cable*capable of transmitting and receiving*signals*(*data*) using*visible light*. See the Wikipediaarticle. Synonym for*Optical fiber cable**fiber optic cable*.**optical quantum computer.**TBD. See*linear optical quantum computing*.**optimal solution.**See*exact solution*. See also:*approximate solution*and*practical solution*.**optimization.**The*process*of*designing*an*algorithm*or*code*so as to make the most effective use of*system resources*, such as to minimize*circuit depth*, minimize use of the*processor*, or minimize use of*memory*(or*qubits*). Alternatively, an*optimization problem*.**optimization problem.**An*application*which seeks to optimize the use of resources in the*real-world*. See*quantum annealing*.**optional requirement.**A*requirement*for a*system*which is preferred and encouraged, even strongly encouraged, but still not absolutely required, in contrast to a*mandatory requirement*which must be met.**oracle.**TBD.**oracle function.**TBD.**oracle qubit.**TBD.**orbital-angular-momentum states.**TBD. Shortened as*OAM states*. Referenced in thearticle.*Researchers achieve multifunctional solid-state quantum memory***order-finding.**TBD. See also:*ordering problem*and*phase estimation*.**ordering problem.**TBD.**organization.**A formalized*group*of individuals who have a common interest and pursue common goals, such as a business or business unit, a government agency, or a non-profit. They have interests, needs, and*goals*, a budget to meet those*goals*, and create*projects*and engage in ongoing*operations*in pursuit of those goals. They use their budget to hire staff for*teams*in both*projects*and*operations*and to buy or lease*products*and*services*for those*projects*and*operations*.**orthonormal.***Vectors*which are all*unit vectors*and all*orthogonal*to each other.**orthonormal bases.**TBD. See also*orthonormal basis vectors*.**orthonormal basis vectors.***Basis vectors*which are*orthonormal*— each is a*unit vector*and they are all*orthogonal*to each other. See the Wikipediaarticle.*Orthonormal basis***outcome.**A future*value*or*situation*, such as the*result*of some*process*which may or may not be under the control of the*user*or*program*expecting that*outcome*. Alternatively, synonym for*result*or*measurement*— a particular*basis state*, |0> or |1>. See also:*expected outcome*,*prediction*, and*outcome basis states*.**outcome basis states.**The possible*outcomes*for a*measurement*, which are the*basis states*, |0> and |1> for a*qubit*.**outcome probabilities.**The*probabilities*for each possible*outcome*for a*measurement*of a*qubit*, one*probability*for each*basis state*, |0> and |1>. The*probability*for an*outcome*is the square of the*modulus*(*magnitude*or*absolute value*) of the*amplitude*(*probability amplitude*) for that*basis state*in the*wave function*for the*quantum state*for the*qubit*. The sum of the*outcome probabilities*for all possible*outcomes*is 1.0, by definition, due to the*principle of unitarity*.**output.**See*output value*. Alternatively,*output data*— all*output values*produced by an*entity*. See also:*input*.**output data.**All*output values*produced by an*entity*. Synonym for*output*. See also:*input data*.**output state tomography.**TBD. See also:*quantum process tomography*and*quantum state tomography*.**output value.**A*data value*or*signal*to be produced by a*system*,*application*,*component*,*device*,*process*,*function*,*mapping*, or*code*. See also:*input value*.**overlapping qubits.**TBD.**P.**Initialism for*polynomial time*. See also:*NP*.**packaging aspects of a quantum computer.**Issues related to the physical construction of a*quantum computer*. How all of the*hardware components*are physically assembled and connected, including the materials used and their thermal characteristics, especially when ultra-cold*superconductors*are being used.**pair.**See*pair of qubits*. Alternatively, two of anything which are closely associated, possibly even*entangled*, such as a*Bell pair*,*Cooper pair*, or*EPR pair*.**pair of qubits.**Two qubits, which may or may not be*connected*(*entangled*.) Generally, indicates that they*are*in fact*connected*(*entangled*.)**pairs.**See*pairs of qubits.***pairs of qubits.**Any number of*pairs*of*connected qubits*(*entangled qubits*.)**parallel processor.**In addition to a*main processor*, a*multiprocessor computer system*may have any number of*parallel processors*, each of which is capable of the*executing*the same types of*programs*as the*main processor*of a*computer system*without*parallel processors*. See also:*secondary processors*, which can*execute*only*specialized software*rather than arbitrary*programs*as can be done by a*main processor*.**parameter.**See*function parameter*. Alternatively, a*configuration parameter*.**parameterized ansatz circuit.**TBD.**parametric gates.**TBD. See thepaper by Didier, Sete, da Silva, Rigetti. See also:*Analytical modeling of parametrically-modulated transmon qubits**parametrically-activated entangling gates*.**parametrically-activated entangling gates.**TBD. See thepaper by Didier, Sete, da Silva, Rigetti. See also:*Analytical modeling of parametrically-modulated transmon qubits**parametrically-modulated transmon qubits*.**parametrically-modulated transmon qubits.**TBD. See thepaper by Didier, Sete, da Silva, Rigetti. See also:*Analytical modeling of parametrically-modulated transmon qubits**parametrically-activated entangling gates*.**parametrized ansatz state.**TBD.**parent class.**The*OOP class*from which a*subclass*was*derived*. Also its*superclass*.**partial output state tomography.**TBD.**partial trace.**TBD.**partially connected.**See*partially entangled*.**partially entangled.**Some but not all possible*pairs of qubits*of a*quantum computer*may be*entangled*simultaneously, in contrast with*fully entangled*, where all possible*pairs of qubits*may be entangled. Technically,*minimally entangled*is also*partially entangled*, but the latter indicates more extensive*entanglement*, and the former indicates how limited the*entanglement*is.*Partially entangled*will also be*highly entangled*if most*pairs of qubits*are indeed*entangled*.**particle.**An extremely small, localized*object*. Can range in size from a*subatomic particle*(*elementary particle*),*photon*,*free electron*,*atom*or*ion*, or*molecule*, to fine powders. Generally, in the context of*quantum computing*and*quantum mechanics*,*particle*will refer to an*electron*,*photon*,*ion*, or an*atom*or*molecule*in some cases.**particle swarm optimization.**TBD. Abbreviated as*PSO*.**passive error suppression.**TBD.**password.**A secret*character sequence*used as a*security measure*to provide*security*for*data*and*systems*. See also:*cryptographic key*.**pattern recognition.**TBD.**pattern recognition tasks in machine learning.**TBD.**pauli.**See*Pauli*— should be capitalized since it is a person’s*proper name*.**Pauli.**Wolfgang Pauli — physicist, pioneer in*quantum mechanics*, discoverer of the*exclusion principle*— now known as the*Pauli exclusion principle*. See the Wikipediaarticle.*Wolfgang Pauli***Pauli correction.**TBD.**Pauli error.**TBD.**Pauli error rate.**TBD.**Pauli exclusion principle.**Loosely, and somewhat inaccurately, two*particles*with*mass*(excludes*photons*) can not be in the same place at the same time. It’s a little more complicated than that, but it differentiates a lot of the behavior of*electrons*,*protons*,*neutrons*,*atoms*, and*molecules*from*photons*— again, loosely and a bit inaccurately. Synonym for*exclusion principle*. See the Wikipediaarticle for a more accurate but difficult description.*Pauli exclusion principle***Pauli frame.**TBD.**Pauli gate.**TBD.**Pauli gate error.**TBD.**Pauli generator.**TBD. See*Pauli generators of the Clifford group*.**Pauli generators of the Clifford group.**TBD. Referenced in thepaper by Reagor, et al.*Demonstration of Universal Parametric Entangling Gates on a Multi-Qubit Lattice***Pauli group.**TBD. See thepaper by Helsen, Wallman, Wehner.*Representations of the multi-qubit Clifford group***Pauli measurement.**TBD. See theweb page from Microsoft.*Pauli measurements***Pauli operator.**TBD.**Pauli principle.**See*Pauli exclusion principle*.**Pauli resetting.**TBD.**Pauli sequence.**TBD.**Pauli twirling.**See*Pauli twirling approximation*.**Pauli twirling approximation.**TBD. Abbreviated as*PTA*. See thepaper by Geller and Zhou.*Efficient error models for fault-tolerant architectures and the Pauli twirling approximation***Pauli-X gate.***Quantum logic gate*(*operation*) which reverses the states of |0> and |1> for a single*qubit*. This is accomplished by a rotation of the*Bloch sphere*about the X-axis by*pi*radians. This is comparable, to the Boolean*NOT*operation. Abbreviated as*X*or*X gate*. See the Wikipediaarticle.*Quantum logic gate***Pauli-Y gate.***Quantum logic gate*(*operation*) which rotates a single*qubit*by*pi*radians about the Y-axis. This is accomplished by a rotation of the*Bloch sphere*about the Y-axis by*pi*radians. Abbreviated as*Y*or*Y gate*. See the Wikipediaarticle.*Quantum logic gate***Pauli-Z gate.***Quantum logic gate*(*operation*) which rotates a single*qubit*by*pi*radians about the Z-axis. This is accomplished by a rotation of the*Bloch sphere*about the Z-axis by*pi*radians. Abbreviated as*Z*,*Z gate*, or*R-pi*. See the Wikipediaarticle.*Quantum logic gate***PCB.**Initialism for*printed circuit board*.**PEA.**Initialism for*phase estimation algorithm*. See also*QPE*.**performance.**How much work a*computer*can accomplish in a given*unit*of time. See also:*high performance*and*capacity*.**period finding.**TBD. See also:*order-finding*and*phase estimation*.**period of time.**See*interval of time*.**peripheral device.**A*device*which is attached to a*computer*and performs some secondary*function*other than actual*computation*, including*storage*, display, output, input, or communication.**PFCQC.**Initialism for*Practical Fully-Connected Quantum Computer Challenge*.**phase.**Generally, stages of a sequence of activities or*processing steps*. Also, in the physics of*waves*, refers to both the*frequency*of a wave and the timing of the*zero-crossing*of the wave, which can be expressed either as*time*or the angle in radians which the wave would transit in that time. Also referred to as*sign*. See the Wikipediaarticle. See also*Phase (waves)**phase difference*and*phase shift*. Alternatively, a fraction of a full circle — an angle in radians divided by two pi, so that a phase of 1.0 would correspond to an angle of two pi radians or 360 degrees and a 90-degree angle would be a phase of 0.25. Alternatively, particularly if written in all caps as*PHASE*, see*PHASE gate*.**PHASE.**See*PHASE gate*.**phase coherence time.**TBD.**phase damping.**TBD.**phase difference.**The difference between the*phases*of two*waves*. Can be expressed either as the*time*distance between their*zero crossings*, or as the angle in radians that the wave would transit during that time to account for the difference in the*zero crossings*of the two waves.**phase estimation.**TBD. See also:*period finding*and*order-finding*.**phase estimation algorithm.**See*quantum phase estimation algorithm*. Abbreviated as*PEA*.**phase flip error.**A*quantum error*where the*phase*or*sign*of a*qubit*is*flipped*. [TBD: vague, technical, more detail] See the Wikipediaarticle.*Quantum error correction***PHASE gate.**Synonym for the*RZ gate*. A*quantum logic gate*which rotates a*qubit*about the Z-axis by a specified angle, in radians. Abbreviated as*PHASE*.**phase kickback.**TBD. See theWeb page from Quora.*What is phase kickback and how does it occur?***phase shift.**A change in the*zero crossing*of a*wave*. Generally a shift in*time*to move the*zero crossing*, which can also be expressed as the angle in radians that the*wave*would transit during that*time*to shift the*wave*. Alternatively, a change in the angle of rotation about the vertical, Z axis of the Bloch sphere, commonly known as phi, measured in radians or degrees.**phase shift gate.**A quantum logic gate which shifts the*phase of a qubit*— the angle of rotation about the vertical, Z axis of the Bloch sphere, commonly known as phi, measured in radians or degrees, commonly known as*phi*. See*phase shift (R-phi) gates*.**phase shift (R-phi) gates.**A family of q*uantum logic gate*(*operation*) which modify the*phase*of a single*qubit*. [TBD: vague, technical more detail] See the Wikipediaarticle.*Quantum logic gate***phase of a qubit.**The angle of rotation of the state of a qubit about the vertical, Z axis of the Bloch sphere, commonly known as phi, measured in radians or degrees, commonly known as*phi*.**phase qubit.**A*qubit*based on the*phase*difference between two*superconductors*. [TBD: vague, technical, more detail] See the Wikipediaarticle. See the*Phase qubit*paper. Other types of*Quantum behavior of the dc SQUID phase qubit**qubit*include*charge qubit*,*flux qubit*, and*spin qubit*.**phase term.**TBD. Commonly written as (-1)^x.**phenomena.**More than one instance of a*phenomenon*or more than one type of*phenomenon*.**phenomenon.**An*event or activity*of a*system*that is interesting in some way.**phi.**Refers to the*phase of a qubit*, the angle of rotation of the*quantum state*of a*qubit*about the vertical, Z axis of the*Bloch sphere*, measured in radians or degrees. See also*theta*.**photon.**The smallest*unit*of*visible light*and*electromagnetic radiation*in general.The*elementary particle*which is the fundamental*unit*for transfer of*energy*via*electromagnetic radiation*. A*photon*is a*boson*. A*photon*is*massless*. A*photon*behaves more like a*wave*than a*particle*, but it is both. The energy of a*photon*is proportional to its*frequency*. See the Wikipediaarticle.*Photon***photographic image.**An*image*which was*captured*using a*camera*, either a*digital camera*of a scan of a hard-copy photograph. See also:*graphical image*.**photonic.**Relating in some way to*light*and*photons*.**photonic quantum computation.**TBD.**photonic quantum computer.**TBD.**photonic quantum computing.**TBD. Synonym for*quantum photonic computing*. See also:*quantum photonic processor*.**photonic quantum computing chip.**TBD.**photonic quantum processor.**TBD.**phrase.**A*pattern*which is a sequence of*words*,*keywords*,*numbers*, or other semantically significant*entities*, usually within a*textual value*. Usually excludes*punctuation*.**physical.**Relating to*entities*and*conditions*in the*real world*, in contrast to*entities*and*conditions*in a*computational environment*. See also:*physical environment*.**physical body.**A localized*object*, having some distinction from surrounding*matter*.**physical classical computer.**The hardware for a*classical computer*, in contrast to a*simulated classical computer*or a*virtual machine*. See also*physical classical system*.**physical classical system.**Generally, a reference to a*physical classical computer*. See also:*real classical system*.**physical computer.**The*hardware*for a*computer*. See*physical system*. An*actual computer*, in contrast to a*simulated computer*.**physical computer system.**Either a synonym for*physical computer*or a*physical computer*combined with any additional*devices*or equipment needed to support the operation of the*computer*. May or may not include the*computer software*which may be needed to use the*computer*in order to solve*problems*.**physical connection.**A*connection*between two or more*devices*using some*solid medium*, such as*wiring*,*cabling*,*fiber optic cable*, or a*waveguide*, in contrast with*wireless connection*(or no*connection*.)**physical entity.**Any*object*, structure, or*phenomenon*in the*physical world*, in contrast to a*computational entity*.**physical environment.**The physical*conditions*immediately surrounding and near a*physical entity*, including location, altitude, orientation, temperature, air pressure, humidity, wind, weather,*electromagnetic radiation*, solar radiation, cosmic radiation, background radioactive decay, vibration, and movement of other*physical entities*, any of which may have a physical impact or influence.**physical error rate.**The percentage of the*time*that a given*quantum logic gate*will be compromised by a*quantum error*, such as*noise*from the environment or*decoherence*in general. 1% is common today. See also:*quantum error correction (QEC)*and*quantum error mitigation*.**physical gate.**See*physical logic gate*.**physical logic gate.**See*quantum physical logic gate*, for the purpose of*quantum error correction*. Otherwise, the reference is simply to the physical hardware, such as the*silicon semiconductor*which performs a*logic operation*, either*classical*or*quantum*— a*classical logic operation*or a*quantum logic operation*. Alternatively, a*classical logic gate*on an*integrated circuit*or*printed circuit board*.**physical object.**An*object*which exists in the*real world*, in contrast to a*computational environment*.**physical operation.**An*operation*which can be performed on a*physical qubit*, including*preparation*,*logic gate execution*, and*measurement*.**physical quantum bit.**The*hardware*which implements a*qubit*. Alternatively, a*qubit*on an*actual quantum computer*, in contrast to a*quantum computer simulator*. See also:*logical qubit*. Alternatively, one of a collection of*qubits*which collectively represent a single*quantum logical qubit*for the purpose of*quantum error correction*(*QEC*).**physical quantum machine.**See*physical quantum computer*,*physical quantum system*, or*physical quantum computer system*.**physical quantum computer.**The*hardware*for a*quantum computer*. Alternatively, an actual*quantum computer*, both*hardware*and*software*, in contrast to a*simulated quantum computer*.**physical quantum computer system.**Either a synonym for*physical quantum computer*or a*physical quantum computer*combined with any additional*devices*or equipment needed to support the operation of the*quantum computer*. May or may not include the*computer software*which may be needed to use the*quantum computer*in order to solve*problems*.**physical qubit.**A*qubit*on a*physical quantum computer*, in contrast to a*simulated quantum computer*. Alternatively, one of a collection of*qubits*which collectively represent a single*logical qubit*for the purpose of*quantum error correction*(*QEC*).**physical qubit calibration.**Testing and tuning of the*hardware*parameters for*hardware*control of a*physical qubit*. This needs to be done on a fairly frequent and fairly regular basis. See thepaper by Kelly, O’Malley, Neeley, Neven, Martinis of Google. IBM says they calibrate their*Physical qubit calibration on a directed acyclic graph**Q Experience**quantum computer*twice a day. See also:*recalibration*.**physical machine.**See*physical computer*or*physical system*.**physical medium.**The*material*(*medium*) in which*matter*,*energy*, or*information*is*transmitted*or*stored*.**physical quantity.***Quantity*or*quality*of a*physical system*.**physical quantum system.**Generally, a reference to a*physical quantum computer*or*physical quantum computer system*. Alternatively, a reference to a collection of*physical bodies*,*particles*,*waves*, gases, and liquids which are to be analyzed or modeled according to the principles and methods of*physics*, either*classical mechanics*for*bodies*,*quantum mechanics*for*particles*and*waves*, or*statistical mechanics*for gases and liquids. See also:*real physical system*and*real quantum system*.**physical system.**Generally, a reference to a*physical computer*, such as a*classical computer*or a*quantum computer*. Alternatively, especially in the context of a*programmable quantum simulator*, a reference to a collection of*physical bodies*,*particles*,*waves*, gases, and liquids which are to be analyzed or modeled according to the principles and methods of*physics*, either*classical mechanics*for*bodies*,*quantum mechanics*for*particles*and*waves*, or*statistical mechanics*for gases and liquids. See also:*real physical system*,*real classical system*,*real quantum system*.**physical world.**Anywhere in the universe, in contrast to a*computational environment*. Synonym for*real world*.**physically-motivated ansatze.**TBD. Abbreviated as*PMA*. In contrast to*hardware heuristic ansatze*(*HHA*).**pi.***Value*of*pi*. Or at least an approximation. The*mathematical constant*which is the ratio of the circumference of an ideal circle to its diameter.**pi Josephson junction.**A*Josephson junction*in which the*phase*is*pi*.**planar.**On the same flat, two-dimensional plane, in contrast to three-dimensions or multiple planes.**planar lattice design.**An arrangement of*hardware components*, such as*devices*on an*integrated circuit*, in the same flat, two-dimensional plane, in an approximately*grid-like*configuration. A style of*chip layout*.**Planck constant.**The smallest increment of*energy*in a*photon*. [TBD: verify] Or, the*energy*of a*photon*divided by its*frequency*. The*energy*of a*photon*being its*frequency*, in*hertz*or cycles per second, times the*Planck constant*. See Wikipediaarticle. Denoted by*Planck constant**h*. See also:*reduced Planck constant*.**Planck’s constant.**See*Planck constant*.**plasma.**Hot,*ionized gaseous matter*. See also:*solid*,*liquid*, and*gas*.**plasma matter.***Matter*in the form of*plasma*. See also:*solid matter*,*liquid matter*, and*gaseous matter*.**plasma medium.**A*medium*comprised of*plasma*, in contrast with*solid medium*,*liquid medium*, or*gaseous medium*. See also:*plasma matter*.**PMA.**Initialism for*physically-motivated ansatze*. See also:*HHA*.**polarised microwave.**TBD. Referenced in thepaper by Nagata, Kuramitani, Sekiguchi, and Kosaka. See also:*Universal holonomic quantum gates over geometric spin qubits with polarised microwaves**circularly polarised microwave*.**polycephalic quantum computer.**A particular characterization of*quantum computers*by physicist Stephen Blaha. See thepaper. Polycephaly simply mean having more than one head, suggestive of a multi-tape, multi-head Turing machine.*A Quantum Computer Foundation for the Standard Model and SuperString Theories***polynomial.**See*polynomial time*and*polynomially*.**polynomial rate.**See*polynomial time*.**polynomial time.**An*algorithm*whose*cost*or*complexity*grows*polynomially*as its*input*grows, in contrast to*exponential time*. A key goal and benefit of*quantum computers*is that*algorithms*take only*polynomial time*for*problems*which the best*algorithms*on a*classical computer*take*exponential time*. Class of*problems*which can be solved by*algorithms*having a number of steps polynomial in the input size. Abbreviated as*P*. See also:*nondeterministic polynomial time*. See the Wikipediaarticle.*Time complexity***polynomially.**A*number*raised to a relatively small power, in contrast to*exponentially*— a relatively small*number*raised to the*nth*power. It grows much slower, which is much better, and the hallmark of the*quantum advantage*. In contrast to*superpolynomially*.**position.**Location of an*object*or other*entity*in*space*. See also:*direction*,*distance*, and*velocity*.**positive operator-valued measure.**TBD. Abbreviated as*POVM*.**post-classical computing.**Any form of*computing*which is more advanced than*classical computing*. Such as*quantum computing*.**post-Moore’s Law era.**The period following the breakdown or deceleration of*Moore’s Law*, when the density of*transistors*on an*integrated circuit*is no longer doubling every couple of years. That’s a negative for*classical computing*, but an opportunity for*quantum computing*. We may be in a transition period where doubling of*transistor density*has slowed from every two years to between two and a half years to three years. What the future holds out three to five to ten years is quite murky at this stage.**post-processing.**See*post-processing of final results*.**post-processing of final results.**Processing of*measurement results*on a*classical computer*after execution of a*quantum circuit*which occurred on a*quantum computer*, either a*physical quantum computer*or a*simulated quantum computer*.**post-processing phase.**See*post-processing of final results*.**post-quantum cryptography.**In the*post-quantum cryptography era*, new methods are needed which cannot be cracked with a*quantum computer*. Although, such methods do not exist, yet. See also:*quantum-proof cryptography*,*quantum-resistant cryptography*,*quantum-safe cryptography*,*quantum-proof*,*quantum-safe*, and*quantum-resistant*. See the Wikipediaarticle. See the NIST*Post-quantum cryptography*web page. Abbreviated as*Post-Quantum Cryptography**PQC*.**post-quantum cryptography era.**The era when*traditional modern cryptographic methods*can be readily cracked using a*quantum computer*, so new methods are needed which cannot be cracked with a*quantum computer*. See also:*quantum-proof*,*quantum-safe*, and*quantum-resistant*. See the Wikipediaarticle. See the NIST*Post-quantum cryptography*web page.*Post-Quantum Cryptography***post-quantum cryptography standardization.**TBD. See*post-quantum cryptography*and the NISTweb page. Abbreviated as*Post-Quantum Cryptography**PQC standardization*.**post-quantum cybersecurity.***Cybersecurity*in the era of*post-quantum cryptography*, when*traditional modern cryptographic methods*can be cracked by*quantum computers*and newer methods of cryptography are needed, which are*quantum-proof*,*quantum-resistant*, and*quantum-safe*.**post-selected ancilla.**TBD.**post-selection.**TBD.**post-selection (ancilla verification).**TBD.**post-selection and purification.**TBD.**PostBQP.**Short for*postselected bounded-error quantum polynomial time*.**postselected bounded-error quantum polynomial time.***Bounded-error quantum polynomial time*(*BQP*) with*postselection*. Any*problem*which can be*solved*on a*quantum computer*in*polynomial time*correctly at least two-thirds of the time — errors are bounded to no more than one-third of the time — and which has an additional*output qubit*which can be selected (*measured*) for the |1>*basis state*. Abbreviated as*PostBQP*. See the Wikipediaarticle and the*PostBQP*paper by Aaronson. See also:*Quantum Computing, Postselection, and Probabilistic Polynomial-Time**postselected bounded-error quantum polynomial time*or*PostBQP*.**postselection.**See*postselection qubit*and*PostBQP*.**postselection qubit.**An additional*output qubit*of a*quantum circuit*which can be*measured*for the |1>*basis state*. See also:*postselected bounded-error quantum polynomial time.***POVM.**Initialism for*positive operator-valued measure*.**power.**See*electrical power*. Alternatively, synonym for*high performance*.**power grid.**See*electrical power grid*.**power plant.**See*electrical power plant*.**power source.**See*electrical power source*.**power supply.**See*electrical power supply*.**powerful.**See*high performance*.**PQC.**Initialism for*post-quantum cryptography*.**PQC standardization.**Short for*post-quantum cryptography standardization*.**practical.**Relates to*real-world problems*. Alternatively, relates to a level of effort and resources which is considered reasonable and not excessive. See also:*practical problem*,*practical solution*,*practical needs*,*practical cost*, and*practical project*.**practical application.**An*application*which addresses a*practical problem*at a*practical cost*.**practical cost.**The financial and lost-opportunity cost of a project is considered acceptable and not excessive. It won’t break the budget or put other projects at risk.**practical fully-connected quantum computer.**A*fully-connected quantum computer*which is not only theoretically possible, but can be*practically*constructed today, emphasizing that any*qubit*can be*entangled*with any other*qubit*, rather than being limited to to only certain*pairs of qubits*.**Practical Fully-Connected Quantum Computer Challenge.**An NSF project for a*practical fully-connected quantum computer*. Abbreviated as*PFCQC*.**practical problem.**A*problem*which is of*practical interest*to an organization or individual, in contrast to a*theoretical problem*, a*research problem*, or an*experimental problem*. Its*solution*meets needs of*users*and the organization. See also:*real-world problem*and*practical, real-world problem*.**practical interest.**Relating to the reasonable and pressing needs and interests of a*user*or organization, and for which a*solution*is considered*practical*.**practical need.**See*practical problem*and*practical interest*.**practical project.**A*project*which is*technically feasible*, has a reasonable cost, and addresses a significant*real-world problem*of*practical interest*to the organization. See also:*practical problem*and*practical cost*.**practical quantum computer.**See*viable quantum computer*, with emphasis on the extent to which real,*practical problems*can be solved using the*quantum computer*. Alternatively, a*theoretical quantum computer*which would be a*viable quantum computer*if it were to be built, eventually. Alternatively, a*quantum computer*which is both a*viable quantum computer*and a*current quantum computer*.**practical quantum computing.***Computing*with a*practical quantum computer*. Active use of a*practical quantum computer*. Using a*quantum computer*to produce*practical solutions*to*practical problems*.**practical quantum supremacy test.**There is no universally agreed upon benchmark test for what exactly constitutes*quantum supremacy*. This paper,, is one proposal for a*Characterizing Quantum Supremacy in Near-Term Devices**quantum supremacy test*.**practical, real-world problem.**Redundant, but emphasizes the need to focus on*practical problems*and*real-world problems*, coupled with*practical, real-world solutions*.**practical, real-world solution.**Redundant, but emphasizes the need to focus on*practical solutions*and*real-world solutions*— for*practical, real-world problems*.**practical-scale quantum computer.**See*practical quantum computer*, emphasizing sufficient*capacity*(*qubit count*) for*real-world problems*.**practical solution.***Solution*which satisfies*practical needs*and requires only a practical level of effort, resources, and cost even if not an*optimal solution*. It’s good enough. See also:*approximate solution*,*exact solution*,*practical cost*,*real-world solution*, and*practical, real-world solution*.**precise solution.**See*exact solution*.**prediction.**Either*speculation*or the use of a*theory*to deduce an expected*outcome*.**preparation.**See*quantum logic circuit preparation*.**preparation logic.**See*quantum logic circuit preparation*.**preparation phase.**See*quantum preparation phase*. See also*execution phase*and*measurement phase*.**preparation steps.**See*quantum logic circuit preparation*.**present-day quantum hardware.**See*current quantum computer*or*current general purpose quantum computer*.**primary control logic.**See*control logic*and*host program*.**prime.**See*prime number*.**prime number.**An*integer*for which there is no collection of*integers*other than 1 and itself which can be multiplied together to produce the original*integer*. See also:*encryption key*and*prime factorization*.**prime factorization.**See*prime factorization problem*. See thepaper by Shor. See also:*Polynomial-Time Algorithms for Prime Factorization and Discrete Logarithms on a Quantum Computer**factoring integers*.**prime factorization problem.**The subset of the*integer factorization problem*where the collection of of*integers*whose product is the original*integer*has exactly two integers, both of which are*prime*. This is the essence of cracking an*encryption key*, which is a very large*integer*which is the product of two reasonably large*prime numbers*. See the Wikipediaarticle. See also:*Integer factorization**crack a cryptographic key*.**primitives.**TBD.**principle of unitarity.**See*unitarity*. The sum of the*probabilities*for all possible*outcomes*for a*quantum system*is 1.0, by definition.**principles of operation.**A general and*detailed specification*and description of everything that a*software developer*needs to know to work with a*system*directly, without any intervening layers of*software*, not even an*operating system*. This does not detail the internal*implementation*of the*system*, only the details that the*software developer*can observe, detect, and control. An*architecture specification*will typically include more of the internal detail. For a*software system*, the*functional specification*and*API specification*should be sufficient. For a*hardware system*, such as a*computer*, the*principles of operation*would be equivalent to the*functional specification*and*API specification*for*software*. See also:*programming model*.**principles of quantum computing.**See*quantum computing principles*.**principles of quantum mechanics.**The principles of*quantum mechanics*, especially*superposition*,*entanglement*, and*quantum decoherence*.**printed circuit board.**Flat, non-conductive sheet of*material*upon which the*electronic components*, including both*discrete electronic components*and*integrated circuits*, and their*interconnections*for an*electronic circuit*can be etched and fastened, in contrast to an*integrated circuit*. See the Wikipediaarticle. Abbreviated as*Printed circuit board**PCB*.**probabilistic result.**The*quality*of*measurement*and*results*on a*quantum computer*, which gives them at least somewhat of a*nondeterministic quality*, due to the underlying nature of*quantum mechanics*, upon which*quantum computers*are based. See also:*probability amplitude*,*deterministic result*, and*nondeterministic result*.**probability.**Chance or likelihood of a given*outcome*or of a*quantum system*being in a particular*quantum state*. A*real number*which is the square of the*modulus*of the*probability amplitude*of a*quantum state*— the sum of the squares of the*real part*and*imaginary part*of the*probability amplitude*. A*number*between 0.0 and 1.0. The sum of the*probabilities*of all possible outcomes or all possible*quantum states*is, by definition, 1.0. See also:*probability amplitude*.**probability amplitude.**A*complex number*which is the representation in the*wave function*of a*quantum system*, such as a single*qubit*or collection of*qubits*, of the*probability*that the*quantum system*is in a particular*quantum state*. It is not the actual*probability*, but the square of the*modulus*of the*probability amplitude*is the actual*probability*— the*modulus*of the*probability amplitude*is the square root of the*probability*. The sum of the*probabilities*(not*amplitudes*) for all possible*quantum states*of the*quantum system*(a single*qubit*or collection of*qubits*) is, by definition 1.0. See the Wikipediaarticle. See also:*Probability amplitude**eigenvalues and eigenvectors*and*quantum amplitude*.**probability distribution.**The*probability*of each possible outcome or*quantum state*over some*interval*of all or a subset of all possible outcomes or*quantum states*. See the Wikipediaarticle.*Probability distribution***problem.**A*situation*which is considered undesirable or otherwise problematic for some reason and in need of a*solution*, to transform the*situation*to a more optimal*situation*. A*problem*may be a*practical problem*, a*research problem*, or a*theoretical problem*. See also*opportunity*and*solution*.**process.**A*computer program*which is*executing*has its own*state*independent of other*processes*which are*executing*on the same*computer*. The*operating system*is responsible for scheduling the*execution*of*processes*, especially when there are more*processes*or*programs*than*processors*on the*computer*, and also responsible for saving and restoring or switching*state*when*execution*switches between*processes*. This concept exists only on*classical computers*at this time — there is no equivalent concept on a*quantum computer*. Alternatively, some sequence of*steps*required to accomplish some*task*or to achieve some*goal*, with a beginning, middle, and end. Alternatively, a reference to*processing*.**process communication.**See*interprocess communication*.**process fidelity.**TBD.**process synchronization.**The ability of two*processes*to*synchronize their execution*, either to assure that they*execute*at the same time, or to assure that they do not.**processed measurement results.**See*post-processing*.**processing.**The act or activity of sequencing through the*steps*of a*process*. See also:*processing step*.**processing step.**One of the series of*steps*in a*process*.**processor.**The main, central portion of a*computer*, where the bulk of*computation*is performed. Alternatively, a*secondary processor*or*parallel processor*of a*multiprocessor computer system*. See also:*central processing unit*(*CPU*).**processor chip.**A*processor*which is fully implemented using a single*integrated circuit**chip*.**product.**A*physical object*which a*vendor*is offering for*customers*to purchase or lease, in contrast to a*research project*or*technology*which is not yet fully*developed*and available for purchase. See also*service*.**product development.**The*process*of constructing a*product*. See also:*software development*and*product development stage*.**product development process.**The*process*which is to be used to construct a*product*. See also:*product development*,*software development,*and*product development stage*.**product development stage.**The stage in the*development*of*product*based on a*technology*where the*research stage*and the*experimental stage*have been completed and there is no question about the practicality of*products*based on the*technology*. Upon completion of the*product development stage*, the*technology*and*product*will re ready for the*commercial availability stage*. Alternatively, any of the numerous stages of*product development*, stages or steps in the*product development process*.**product form.**TBD.**product formula algorithm.**TBD.**product state.**TBD. See the Wikipediaarticle. See also:*Separable state**separable state*and*entangled state*.**production.**Actual use of a*technology*,*product*,*service*, or*system*in the*real world*, serving*end-users*with*real-world applications*. See*production deployment*.**production deployment.**The stage after*development*where a*technology*,*product*,*service*, or*system*is not only*production-ready*, but is actually put into*production*, use, serving*end-users*with*real-world applications*, in contrast to*experimentation*and*testing*.**production-ready.**A*technology*,*product*,*service*, or*system*is ready to be put into*service*(*production*) serving*end-users*for*real-world applications*, in contrast to*experimentation*and*testing*. Implies that*experimentation*and*testing*have been completed.**program execution.***Execution*of a*computer program*. See*quantum program execution*. Alternatively,*execution*of a*classical computer program*.**programmer.**An individual who engages in*programming*. A*computer programmer*or a*quantum programmer*. Also a*software developer*.**programmable quantum simulator.**A*quantum program*which implements*programmable quantum simulation*to*simulate*the*quantum physics*of a*physical system*.**programmable quantum simulation.**The use of a*quantum computer*to*simulate*the*quantum mechanics*of a*physical system*— the actual*physics*. Technically the*quantum computer*could be a*quantum computer simulator*running on a*classical computer*, but the raw computational power needed to*simulate quantum physics*would tend to require the raw*power*of a*physical quantum computer*. See thepaper by Hayes, Flammia, and Biercuk, and the*Programmable Quantum Simulation by Dynamic Hamiltonian Engineering*paper by Brown, Munro, and Kendon.*Using Quantum Computers for Quantum Simulation***programming.**The*development*of*computer programs*, either for a*classical computer*or a*quantum computer*. Both*design*and*coding*. The process of implementing*algorithms*. May or may not include*design*and*development*of the*algorithms*themselves. See also:*software development*. Also*computer programming*and*quantum programming*.**programming language.**The*language*used to express a*computer program*. May range from*assembly language*to*high-level languages*, even to*higher-level languages*. See also:*specialized programming language*.**programming language compiler.**A*software tool*which can*transform*the*source code*for a*computer program*into a form more suitable for*execution*, either the final*executable code format*or an*intermediate representation*. May be shortened to*compiler*.**programming model.**A*detailed specification*of the*features*of a*computer*or*system*which the*developer*may use and the*rules*which they must follow, as well as guidance for how*real-world problems*can be mapped into use of the*capabilities*of the*computer*and its*software*. In short, how the*programmer*can*program*the*computer*effectively. Alternatively, a brief summary of the*features*and*rules*. See also:*quantum abstract machine*,*instruction set architecture*, and*principles of operation*.**programming of quantum computers.***Programming*with the intent of executing the*program*on a*quantum computer*.**project.**A*group*of*professionals*and other*individuals*who have been brought together for a*purpose*, to achieve a*goal*or to pursue an*interest*, such as to*develop*a*product*. See also:*team*and*organization*. Alternatively, as a verb, to*project*— see*projecting*and*projection*.**projecting.**The*process*of mapping (*projecting*) the*wave function*for a*quantum state*to a particular*basis state*, such as |0> or |1> for a*qubit*. See*projection*. See also:*measurement*,*result*, and*outcome*.**projection.**The act of*projecting*the*wave function*for a*quantum state*to a particular*basis state*, such as |0> or |1> for a*qubit*. Alternatively, the*result*of*projecting*the*wave function*for a*quantum state*to a particular*basis state*, such as |0> or |1> for a*qubit*. Synonym for*measurement*or*result*. The*probabilities*, represented as the*amplitudes*or*probability amplitudes*, of the*basis vectors*which comprise the*quantum state*will influence the*result*of the*projection*, but will not guarantee a particular*outcome*, unless the*quantum state*is a*pure state*— not a*superposition*of two*basis states*.**projection postulate.**See*projection postulate of quantum physics*.**projection postulate of quantum physics.**TBD.**projective measurement.**TBD. See also:*general measurement*and*projection*.**projector.**TBD.**promise of quantum computing.**Vague notion of a perceived advantage of*quantum computing*over*classical computing*for both*performance*and*capacity*. Has yet to be*quantified*. In theory it will be significant, but this has yet to be proven as much more*research*and*development*remains needed.**proper name.**Formal*name*for an*individual*, either for a person, place, or a non-person as if they were a person, intending to acknowledge their social significance rather than being a strictly arbitrarily assigned*identifier*.**property.**An aspect of an*entity*which can be observed, measured, detected, or modeled, directly or indirectly. Synonym for*characteristic*,*quality*, and*attribute*.**proposal.**An effort and*document*advocating for either a new*project*or the*acquisition*of a*product*or*service*, seeking*management approval*after*management review*.**protocol.**A collection of*data formats*,*rules*, and*processes*for*communicating*between two or more*devices*, such as*computers*. See also:*digital protocol*and*Internet protocol*.**prototype.**A subset or approximation of a*product*implemented for the purpose of*experimentation*and*demonstration*of a*nascent technology*or*conceptual approach*. Feedback from working with a*prototype*can then be used to firm up plans for the*real product*. See also:*working prototype*.**prototyping.**The*process*of*validating*,*testing*,*evaluating*, and*demonstrating*proposals for a*product*or*service*by building a*prototype*which can actually*function*as desired, or at least*approximate*the desired*function*. See also:*working prototype*.**PSO.**Initialism for*particle swarm optimization*.**PSWAP.**See*PSWAP gate*.**PSWAP gate.**A*quantum logic gate*which swaps the*quantum state*of two*qubits*plus a specified (parameterized)*phase shift*, in radians. The*phase shift*is applied to the first*qubit*if it is in the |1>*basis state*and applied to the second*qubit*if it is in the |0>*basis state*. Abbreviated as*PSWAP*. [TBD: 1) is it a shift of phase or a setting of phase and 2) is the condition before the swap or of the state being swapped in?] Referenced infrom Rigetti Computing. See also:*Source Code Documentation — pyquil.api**SWAP gate*,*CSWAP gate*, and*ISWAP gate*.**PTA.**Initialism for*Pauli twirling approximation*.**public-key.**See*public key*.**public key.**See*traditional modern public key*.**public-key cryptographic algorithm.**See*traditional modern public-key cryptographic algorithm*. See also:*quantum cryptographic algorithm*.**public-key cryptographic method.**See*traditional modern public-key cryptographic method*. See also:*quantum cryptography*.**public-key cryptography.**See*traditional modern public-key cryptography*. See also:*quantum cryptography*.**punctuation.***Characters*used to separate*words*,*numbers*,*names*, or any other semantically significant*entities*in*text*, in an*expression*in some*language*, including both*natural language*and*programming languages*.**pure state.**A*quantum state*which is either a*basis state*, |0> or |1>, or a rotation of a*basis state*. Its*complex vector*will be on the surface of the*Bloch sphere*. In contrast to a*mixed state*, whose*complex vectors*each have an*amplitude*less than 1.0, so that they are now inside rather than on the surface of the*Bloch sphere*. [TBD: verify] See the Wikipediaarticle.*Quantum state***pure state entanglement distillation and dilution.**TBD.**pure-state N-representability conditions.**TBD.**pure-state N-representable manifold.**TBD.**pure-state projection.**TBD.**purity.**TBD.**purity limit.**TBD.**purity measurement.**TBD.

To browse other parts of the glossary:

- Quantum Computing Glossary — Introduction.
- Quantum Computing Glossary — Part 1 — A-C.
- Quantum Computing Glossary — Part 2 — D-G.
- Quantum Computing Glossary — Part 3 — H-P. This part.
- Quantum Computing Glossary — Part 4 — Q.
- Quantum Computing Glossary — Part 5 — R-S.
- Quantum Computing Glossary — Part 6 — T-Z.