Quantum Computing Glossary — Part 2 — D-G

55 min readJul 20, 2018

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

D-G

D-CNOT. Initialism for dynamic controlled-NOT quantum logic gate.
D-CNOT gate. Short for dynamic controlled-NOT quantum logic gate.
D-CNOT logic gate. Short for dynamic controlled-NOT quantum logic gate.
D-CNOT quantum gate. Short for dynamic controlled-NOT quantum logic gate.
D-CNOT quantum logic gate. Short for dynamic controlled-NOT quantum logic gate.
DAQC. Initialism for digital-analog quantum computation.
DAQC paradigm. Short for digital-analog quantum computation paradigm.
data. Raw information to be processed by a computer or output by a computer.
data-driven quantum circuit learning. TBD. Abbreviated as DDQCL. Referenced in the A generative modeling approach for benchmarking and training shallow quantum circuits paper by Benedetti, et al.
data format. How the bits, bytes, and values of a collection of related data are arranged in a sequence or layout suitable for processing, storage, or output by a computer program. See also: common format.
data item. An individual data value, generally with an associated identifier. See also: data record and list item.
data record. A collection of related data items. All of the data items related to a particular entity.
data science. Methods, software, and software tools which focus on extracting knowledge and insight from structured information, unstructured information, and even raw data. See the Wikipedia Data science article.
data storage. The ability to maintain data values for future use. Alternatively, methods for representing data in the physical medium for the purpose of storage. A qubit is a form of data storage.
data structure. A method for organizing data to make it easy to access. The simplest data structures being a record and a list or queue.
data value. A discrete piece of information, such as a single number. See also data item.
database. A specialized organization of storage, usually mass storage but possibly main memory as well, which permits data to be structured, such as in tables, columns, and rows, and easily accessed using keys and queries. Requires database software.
database query. A method of selecting data from a database by specifying criteria which must be met. Such as an SQL query for a relational database. No equivalent for a quantum computer at this stage. See the Wikipedia SQL article.
database server. A server which offers a database service.
database service. Database software running as a software service. This will be necessary rather than the database software simply being a software library if multiple programs, or multiple processes, or multiple computers are accessing the same database at the same time. Application software will communicate with the database service using an API, possibly with a small software library which can offer simpler functions that then access the API for the database service.
database software. Software needed to create and maintain databases. Technically this could be implemented as a software library, but that would only be appropriate if only one program is accessing the database for the duration of the execution of that program. In general, if multiple programs, or multiple processes, or multiple computers are accessing the same database, it will be necessary for the database software to run as a software service in the form of a database service or database server.
DCNOT. Initialism for dynamic controlled-NOT quantum logic gate. Synonym for D-CNOT.
DDQCL. Initialism for data-driven quantum circuit learning.
decimal. See decimal numeral system.
decimal digit. A digit character, 0–9.
decimal numeral system. Method for representing numbers with ten decimal digits, powers of ten, and an integer and fractional part. Synonym for base ten. See Wikipedia Decimal article.
declare. Issue a declaration.
declaration. A non-executable statement which provides information or guidance needed for a compiler or interpreter to properly interpret the meaning of a program written in a high-level programming language, such as declaring a variable or a data structure.
decoherence. See quantum decoherence.
decoherence-avoiding strategies. TBD.
decoherence error. TBD.
decoherence and gate errors. All of the ways that an otherwise valid quantum algorithm can fail to give correct and expected results. See decoherence and quantum logic gate error.
decoherence time. See quantum decoherence time or quantum coherence time — the elapsed time before a qubit or a quantum computer loses coherence — the quantum state of qubits begins to deteriorate. Synonym for coherence time.
decouple qubits from the environment. TBD.
decrypt. See decryption.
decrypt a message. See decryption.
decrypt message. See decryption.
decryption. Decoding of cryptographic messages using cryptographic methods. See also: quantum decryption.
deep circuit. A quantum circuit with a relatively large gate count per qubit. Generally, a lot more gates per qubit than qubits. In contrast to a shallow circuit. [TBD: a number, what’s typical?]
degenerate ground state system. TBD. Referenced in the Universal holonomic quantum gates over geometric spin qubits with polarised microwaves paper by Nagata, Kuramitani, Sekiguchi, and Kosaka.
degenerate V-type qutrit system. TBD. Referenced in the Universal holonomic quantum gates over geometric spin qubits with polarised microwaves paper by Nagata, Kuramitani, Sekiguchi, and Kosaka.
degree of freedom. TBD.
degrees of freedom. TBD.
demonstration. Execution of a program or other process to showcase the capabilities of a technology or application. Not for the user to gain any insights, but for the audience to learn something. See also: experiment, in which which proof to the user and insight for the user are the goal, with no audience per se.
dense coding. TBD. see also: quantum communication.
density functional theory. TBD. See the Wikipedia Density functional theory article. Abbreviated as DFT.
density matrix. TBD.
density operator. TBD.
density operator language. TBD.
dephasing time. How long a qubit can remain in a superimposed state before decaying to a pure |0> or |1> state. Abbreviated as T2 or T2* depending on whether it is measured using the Hahn echo experiment (T2) or the Ramsey experiment (T2*). See also: amplitude coherence time (T1).
depletion mode quantum dots. TBD. See also enhancement mode quantum dots.
depth one population based measurement. TBD.
derivative removal by adiabatic gate. TBD. Abbreviated as DRAG.
derived. In object-oriented programming (OOP), a subclass may be derived from any class.
derived class. See subclass. An OOP class which is derived from another OOP class.
design. Either designing — the process of producing a design, the design process — or the design specification which results from the design process. A design is needed before coding can begin. See also hardware design.
design algorithms. See design of algorithms.
design of algorithms. The conception, construction, evaluation, characterization, and adaptation of algorithms, usually the work of either a computer scientist or a software developer.
design and code. See design and coding.
design and coding. Designing and coding are frequently done together, although they can and generally should be separated.
design goal. An explicit and accepted statement of purpose or a requirement for a system. A strong intention. May be more aspirational than an absolutely mandatory requirement — it may be an optional requirement.
design process. The processes of developing and executing a strategy for transforming an architecture specification into detail of subsystems and individual system components, or transforming a functional specification into a design specification of individual components, or selecting algorithms to accomplish features, functions, and design goals, and transforming one or more algorithms into a workable form that is ready to be transformed more directly into code, although coding itself is not part of the design process. May or may not include development of the algorithms themselves as well. Published algorithms frequently require some degree of adaptation and addition of detail before they can be transformed into code.
design of quantum algorithms. Design of algorithms applied to quantum computation. See quantum algorithm design. See also: quantum algorithm designer.
design spec. See design specification.
design specification. A document which records the result of designing a strategy for implementation of one or more algorithms. A design specification is needed before proceeding to coding of a program. See also: detailed specification, architecture specification, requirements specification, API specification, and functional specification. Commonly abbreviated as design spec.
designer of quantum algorithms. See quantum algorithm designer.
designing. See design process.
desired result. The result which is wanted or expected, in contrast to the result which actually occurred. See also: actual result and expected result.
destructive interference. TBD. In contrast to constructive interference.
detailed specification. A document which lays out in all aspects of a given matter at a very fine granular level, so that all questions are answered and so that there will be no confusion or ambiguity about the matter, such as an architecture specification, design specification, requirements specification, API specification, or functional specification.
detect. See detection.
detect errors. See error detection.
detectable quality. A quality of a system which can be detected. See also: observable quality and measurable quality. See also: detectable quantity.
detectable quantity. A quantity of a system which can be detected. See also: observable quantity and measurable quantity. See also: detectable quality.
detection. Capability of evaluating conditions to determine that some event, condition, or pattern of conditions has occurred, such as to trigger processing of some sort. Such as errors — error detection. See also: mitigation and compensation.
determinism. The quality of a system, process, algorithm, or code by which the starting conditions completely determine the final results. In contrast to nondeterministic.
deterministic. A system, process, algorithm, or code which is governed by determinism — the starting conditions completely determine the final results. In contrast to nondeterministic. See also: deterministic result.
deterministic result. The certainty that results on a classical computer will be as expected (deterministic), while on a quantum computer they will be probabilistic (nondeterministic.) see also: nondeterministic result.
Deutsch (D-theta) gate. A hypothetical three-qubit gate which is conditional on the first two qubits being in the one state. See the Wikipedia Quantum logic gate article.
Deutsch-Jozsa algorithm. TBD. See the Wikipedia Deutsch-Jozsa algorithm article.
develop. See development.
developer. See software developer and programmer.
development. The process of constructing a product or service. See also: software development, product development, and quantum development.
development of quantum applications. TBD. Referenced in National Quantum Initiative Act bill. See also: commercial development of quantum applications.
development tool. A software tool focused on the use of a programming language, such as a compiler or code analysis tool, in contrast to software tools focused on algorithms, design, architecture, and the specific logic of coding.
device. Any piece of hardware which accomplishes some function, ranging from an individual electronic component to a peripheral device to an entire computer or computer system. Generally, in the context of quantum computing it is a reference to a quantum computer.
device ansatz. TBD.
devices that operate beyond the supremacy regime. A quantum computer with a sufficiently large number of qubits, currently more than 50–55 qubits, which is capable of implementing an algorithm which cannot be reasonably implemented on even the largest existing classical computer systems or supercomputers.
DFT. Initialism for discrete Fourier transform or density functional theory.
diabatic process. A process in which environmental conditions or inputs are evolving too rapidly for the system to respond or adapt, leaving the system relatively unchanged, in contrast to an adiabatic process in which the environmental conditions or inputs change slowly enough that the system is able to respond to and adapt to the changing environment and inputs. See the Wikipedia Adiabatic process article.
diagonal. See diagonal of a matrix.
diagonal of a matrix. Either the main diagonal of a matrix or the antidiagonal of a matrix. Successive entries along the diagonal step by one row and one column. For a square matrix the diagonals run from a top corner to the opposite bottom 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 Wikipedia Main diagonal article.
diagonalisation. Alternative spelling for diagonalization.
diagonalise. Alternative spelling for diagonalize.
diagonalization. TBD. Alternatively spelled diagonalisation.
diagonalize. TBD. See diagonalization. Alternatively spelled diagonalise.
diamond vacancy. See nitrogen-vacancy center.
digit. See digit character.
digit character. Character from 0 to 9, at least for base 10. Other number bases will have fewer digit characters.
digits. Sequence of digit characters. May or may not include leading or trailing 0’s, which may or may not have significance depending on context.
digital. Synonym for discrete, in contrast to analog or quantum.
digital-analog quantum algorithm. TBD. See also: digital-analog quantum computation.
digital-analog quantum computation. TBD. Abbreviated as DAQC.
digital-analog quantum computation paradigm. TBD. Abbreviated as DAQC paradigm.
digital camera. A camera which captures photographic images using an image sensor. See also: digital video camera.
digital computer. A computer which processes data as discrete values made up of binary bits, 0 and 1, and collections of binary bits such as bytes, characters, and numbers. It is vague and a matter of debate whether a quantum computer is still a digital computer, especially since the binary bit is generally considered the basis for digital computing. See classical computer, in contrast to quantum computer.
digital circuitry. Hardware, electronic circuitry, which processes and operates on digital signals in the form of classical binary values of 0 and 1, as well as other circuitry needed to transform analog signals to digital signals and to transform digital signals to analog signals.
digital computing. Computing using a digital computer, using discrete data values based on binary bits, 0 and 1.
digital device. See digital computer. Or any device which has a digital interface.
digital electronic component. An electronic component which performs digital logic. See classical digital logic component.
digital Hamiltonian simulation. TBD.
digital interface. A device which is capable of communicating with other devices using digital signals, such as a digital protocol.
digital logic. Logic which uses discrete values, in contrast to analog or quantum logic. See Boolean logic.
digital logic circuit. An electronic circuit using classical digital logic components.
digital protocol. See protocol. For the most part, all protocols involving computers are digital protocols.
digital quantum computation. TBD. In contrast to analog quantum computation (AQC). Abbreviated as DQC.
digital quantum simulation. TBD. In contrast to analog quantum simulation.
digital quantum simulation of chemistry problems. TBD. Not all digital quantum simulation is applied to chemistry problems.
digital quantum simulator. See programmable quantum simulator. Shortened as DQS. see the A digital quantum simulator in the presence of a bath paper.
digital signal. An electronic, magnetic, mechanical, or optical signal which is interpreted as the classical binary values of 0 and 1, in contrast to an analog signal.
digital video. Video which is represented in a digital format, in contrast to traditional video tape analog formats.
digital video camera. A video camera for capturing digital video as a sequence of images using an image sensor, as well as capturing audio in a digital format. See also: video capture and audio capture.
dilution refrigerator. Device for maintaining intense ultra-cold using a mix of two isotopes of liquid helium. The equivalent of a combination of a car’s radiator and air conditioning system for a quantum computer, the part that keeps the chips super-cold. See the Wikipedia Dilution refrigerator article. Synonym for cryostat, but it is really only a portion of the whole cryostat.
dimension. One of the dimensions of a system, such as a quantum system or a vector space, such as a Hilbert space. Essentially, a single vector, which can be scaled to different lengths or magnitudes, but with no change in direction, other than a change in sign.
dimension witness. A method for testing the dimensionality of a quantum system, or more precisely, the dimensionality of the Hilbert space which models the quantum states of a quantum system. See the Testing the Hilbert space dimension paper by Brunner, Pironio, Acin, Gisin, Methot, Scarani.
dimensions. In quantum mechanics and quantum computing, the number of coordinates needed to represent a state (quantum state) in the linear vector space, called a Hilbert space, which models the state space (quantum states, plural) of the quantum system. A single qubit with two quantum states which can be superimposed is modeled with a two-dimensional Hilbert space. Quantum systems can be composed to form larger quantum systems, so that a single qubit is a quantum system and a quantum computer of n qubits is a quantum system as well. When quantum systems are composed in this manner, the dimensionality of the larger quantum system is the product of the dimensionality of the smaller quantum systems of which it is composed. Two qubits are modeled with a four-dimensional Hilbert space (two times two), and a quantum computer with n qubits is modeled with a Hilbert space with 2 to the n dimensions. Higher-dimensionality is possible for individual, small quantum systems, such as a qutrit which is a three-state equivalent of a qubit and has three dimensions, and a qudit which has ten quantum states, all of which can be superimposed for ten dimensions. n qutrits would have a dimensionality of three to the n. n qudits would have a dimensionality of ten to the n. Alternatively, a synonym for dimensionality — the number of dimensions of a system, such as a quantum system. alternatively, a table or matrix has two dimensions — the vertical dimension of rows and the horizontal dimension of columns. See also: higher-dimensional.
dimensional. See dimensions.
dimensionality. Count of dimensions for a system, such as a quantum system.
Dirac notation. Standard notation in quantum mechanics for describing the quantum state of a quantum system. See the Wikipedia Bra–ket notation article. See also: bra and ket. Synonym for bra-ket notation.
direct current. The primary form of electricity used by electronic circuits within computers and other electronic devices, in contrast to alternating current (AC) the primary form of electricity delivered from the power grid to computer systems. Abbreviated as DC. See the Wikipedia Direct current article.
direct embedding. TBD. A programming model for the D-Wave quantum computer. See the Programming with D-Wave: Map Coloring Problem whitepaper and the Solving Set Cover with Pairs Problem using Quantum Annealing paper by Cao, Jiang, Perouli, and Kais. See also: chimera graph.
directed edge. In graph theory, an edge which has a direction. See also: directed graph.
directed graph. In graph theory, a graph whose edges are directed edges. See also: tree.
direction. The orientation of an object or other entity in space. Distinct from the direction of motion component of velocity. See also: position, distance, and velocity.
direction of motion. The direction component of the velocity of an object or other entity in space. Independent of the orientation of the object or entity. See also: direction, distance, and velocity.
discrete. A discrete interval of time, an individual item without any connection to its context, or a physical quantity, such as an energy level, which can only take on a finite number of discrete levels due to the quantum nature of quantum mechanics.
discrete atom. An individual atom, in contrast to material or a device comprised of a significant number of atoms.
discrete Fourier transform. TBD. See the Wikipedia Discrete Fourier transform article. See also: quantum Fourier transform. Abbreviated as DFT.
discrete interval of time. Proceeding in steps in time or at intervals of time, in contrast to continuous. Alternatively, a particular interval of time.
discrete level. One of a finite number of levels of some quantity, in contrast to continuous levels.
discrete logarithm. TBD. See the Wikipedia Discrete logarithm article.
discrete molecule. An individual molecule, in contrast to material or a device comprised of a significant number of molecules.
discrete period of time. See discrete interval of time.
discrete process. See discrete processing.
discrete processing. Processing which occurs at at discrete intervals of time, in contrast to continuous processing which occurs at all moments of time.
discrete steps. See discrete processing.
discrete-time quantum walk. TBD. In contrast to a continuous-time quantum walk. See the Wikipedia Quantum walk article.
discrete value. A specific value. Alternatively, a discrete variable.
discrete variable. A quantity which takes on only a limited number of values, with distinct gaps between the values, in contrast to a continuous value. See also: discrete value.
dispersive qubit readout. See quantum measurement. [TBD: detail, significance] See also: quasi-lumped element resonator.
dispersive readout of a qubit. See dispersive qubit readout.
display. Show information and images to a user. Alternatively, a device for showing information and images to a user.
distance. Spatial separation of two objects or other entities in space. See also: position, direction, and velocity.
distance-based classifier. TBD.
distance-based machine learning model. TBD.
distillable entanglement. TBD.
distillation. TBD.
distinct. A quality or state which can be discerned as separate or different from other qualities or states. Alternatively, an entity which can be discerned as different from other entities.
distinct physical system. TBD.
distributed quantum computation. TBD.
DiVincenzo’s criteria for a quantum computer. Five requirements to fulfill the promise of quantum computation: reliable qubits, ability to initialize qubits — to provide input data, long coherence of qubits, a universal set of instructions for operating on qubits, and a way to retrieve the final state of the qubits after execution of the program has completed. See the The Physical Implementation of Quantum Computation paper by DiVincenzo of IBM.
DMFT. Initialism for dynamical mean-field theory.
domain. See domain of a function. See also: range.
domain of a function. The full set of possible input values for a function. See the Wikipedia Domain of a function article. See also: range of a function.
dot product. TBD. See also: inner product. See the Wolfram MathWorld Dot Product page and the Wikipedia Dot product article.
double-precision floating point. Representation of a real value in 64 bits on a classical computer. Covers values of magnitude from approximately 2.225 times 10 to the minus 308 to approximately 1.798 times 10 to the 308. See the Wikipedia Double-precision floating-point format article. See also: single-precision floating point and extended-precision floating point.
DQC. Initialism for digital quantum computation.
DQS. Initialism for digital quantum simulator.
DRAG. Acronym for derivative removal by adiabatic gate.
DRAG pulse. TBD.
Draper adder. TBD.
dynamic CNOT. Short for dynamic controlled-NOT quantum logic gate.
dynamic CNOT gate. Short for dynamic controlled-NOT quantum logic gate.
dynamic CNOT logic gate. Short for dynamic controlled-NOT quantum logic gate.
dynamic CNOT quantum gate. Short for dynamic controlled-NOT quantum logic gate.
dynamic CNOT quantum logic gate. Short for dynamic controlled-NOT quantum logic gate.
dynamic controlled-NOT gate. Short for dynamic controlled-NOT quantum logic gate.
dynamic controlled-NOT logic gate. Short for dynamic controlled-NOT quantum logic gate.
dynamic controlled-NOT quantum gate. Short for dynamic controlled-NOT quantum logic gate.
dynamic controlled-NOT quantum logic gate. TBD. Abbreviated as D-CNOT. Shortened as dynamic CNOT gate and D-CNOT gate, or dynamic CNOT logic gate, dynamic CNOT quantum gate, dynamic CNOT quantum logic gate, D-CNOT logic gate, D-CNOT quantum gate, and D-CNOT quantum logic gate. Referenced in the Universal holonomic quantum gates over geometric spin qubits with polarised microwaves paper by Nagata, Kuramitani, Sekiguchi, and Kosaka.
dynamic list. See list. In contrast to a fixed-length list.
dynamic system. See dynamical system.
dynamical mean-field theory. TBD. Abbreviated as DMFT.
dynamical system. A system whose behavior changes as a function of time, in contrast to a static system which does not change as a function of time. See the Wikipedia Dynamical system article. See also: chaos theory and quantum chaos theory.
e. Symbolic name for Euler’s number. See the Wikipedia e (mathematical constant) article.
EASE. Initialism for efficient, arbitrary, simultaneously entangling, typically referring to a gate (quantum logic gate), as in an EASE gate.
EASE-based implementation. TBD.
EASE gate. Short for efficient, arbitrary, simultaneously entangling gate.
EASE gate count. TBD.
EASE-gate protocol. TBD.
ECC. Initialism for error-correcting code. See also: ECC memory.
ECC memory. Initialism for error-correcting code memory. See also: quantum error-correction code (QECC) for the equivalent for a quantum computer.
edge. In graph theory, a connection or relationship between two nodes in a graph. Edges can be directed or undirected — directed edge or undirected edge. A graph based on directed edges is a directed graph, and a graph based on undirected edges is an undirected graph. See also: root, branch, and leaf.
edge case. An outlier or fringe condition of a phenomenon, in contrast to normal conditions. A situation where normal conditions may not necessarily apply, and where algorithms and code may either fail or produce unexpected or unacceptable results.
EDSL. Initialism for embedded domain-specific language.
effect. The result of a cause or action, such as a force acting on an object.
effective XX-Ising interaction. TBD.
efficient algorithms for computationally difficult tasks. TBD.
efficient, arbitrary, simultaneously entangling. TBD. Abbreviated as EASE. Typically used as efficient, arbitrary, simultaneously entangling gate or EASE gate. Referenced in the Efficient Arbitrary Simultaneously Entangling Gates on a trapped-ion quantum computer paper by Grzesiak, et al.
efficient, arbitrary, simultaneously entangling gate. TBD. Abbreviated as EASE gate. Referenced in the Efficient Arbitrary Simultaneously Entangling Gates on a trapped-ion quantum computer paper by Grzesiak, et al.
efficient quantum algorithm. A quantum algorithm whose cost or complexity grows at no worse than a polynomial rate as the number of qubits grows, in contrast to growing at an exponential rate for a classical computer.
efficiently computable function. A computable function for which the length of the computation scales polynomially with the input size. In contrast to an inefficiently computable function which scales superpolynomially with the input size.
eigenenergy. TBD.
eigenfunction. TBD.
eigenphase. TBD.
eigenspace. TBD.
eigenspectrum. TBD.
eigenstate. The mathematical concept in quantum physics of a quantum state for a quantum system which is defined based on linear algebra, represented as a linear combination of eigenvectors, each of which has an eigenvalue. In quantum mechanics, the wave function of a quantum system is a linear combination of eigenstates. In a quantum system, a quantum state is an eigenstate, with the eigenvalue representing the amplitude (probability amplitude), a complex number, the square of whose modulus (magnitude or absolute value) is the probability of the quantum system being in the quantum state represented by its associated eigenvector. In a quantum computer, the quantum state of a qubit is an eigenstate, with distinct eigenvectors for the |0> and |1> basis states. See also: eigenvalues and eigenvectors. Alternatively, a non-superimposed quantum state — a single basis state. [Confirm-TBD?]
eigenvalue. See eigenvalues and eigenvectors. Models the probability that a quantum system (qubit) will be the basis state modeled by the eigenvector associated with the eigenvalue. It models the probability, but is not the actual probability. Rather, it is the amplitude or probability amplitude for the associated eigenvector (basis state), a complex number, the square of whose modulus (magnitude or absolute value) is the actual probability — the square root of the probability is the modulus (absolute value) of the amplitude (probability amplitude.) According to the principle of unitarity, the sum of the probabilities for all of the basis states (basis vectors, modeled as eigenvectors) must be 1.0 — the quantum system must be in some quantum state even if we don’t know which. Measurement of a qubit will produce exactly a single value, one of the basis states, based on the associated eigenvalue, but not in a strictly deterministic manner since it is only a probability, not a certainty. See also: eigenvalue and eigenstate.
eigenvalue estimation. See quantum eigenvalue estimation.
eigenvalues and eigenvectors. The quantum state of a quantum system is modeled as a wavefunction which is a linear combination of the basis states or simplest quantum states of the quantum system, |0> and |1> for a typical quantum computer, each of which is a vector in the vector space for the quantum system, a Hilbert space. Each basis state is modeled by an eigenvector with an associated constant, an eigenvalue, which is the probability amplitude (or simply amplitude) for the quantum system to be in that particular quantum state (basis state.) The amplitude (probability amplitude) is a complex number whose modulus (absolute value) is the square root of the probability that the quantum system is in the quantum state represented by the basis state in the form of its eigenvector — the probability is the sum of the squares of the real part and the imaginary part of the amplitude. The central concept of unitarity requires that the sum of all of the probabilities for each basis state (eigenvector), the value of the modulus (absolute value) of the associated amplitude (probability amplitude) squared, is by definition 1.0. In other words the quantum system has to be in some quantum state, even if we don’t know exactly which one. Each eigenvector corresponds to a measurable quantity or observable quantity of the quantum system. For a quantum computer, each qubit will have two observable quantities, the two basis states of the qubit, |0> and |1>. An operator is defined for each such observable quantity. You cannot observe or measure the actual amplitudes (probability amplitudes), except on a quantum simulator. Rather, measurement will cause the wave function for that observable to collapse, to the value of one of the basis states (eigenvectors) based on the probability (amplitude) at the moment of measurement, but probability will not necessarily produce a deterministic result. The probability for a particular basis state may be 0.0, 1.0, 0.5, or any other value between 0.0 and 1.0. Quantum logic gates are used to initialize (preparation), manipulate (execution), and measure (measurement) the quantum state of qubits. The ultimate value or result of measurement will in fact be one of the basis states, |0> or |1>, but the exact value will be driven by the value of the amplitude associated with the eigenvector for each basis state at the moment of measurement. See the Wikipedia Eigenvalues and eigenvectors article.
eigenvector. See eigenvalues and eigenvectors. Models a basis state, |0> or |1>, for the quantum state of a quantum system, such as a single qubit. See also: eigenvalue and eigenstate.
Einstein-Podolsky-Rosen paradox. An ongoing philosophical dispute among physicists as to whether quantum mechanics with wave functions, without local hidden variables is an adequate account of reality. Not everyone is a believer, but the general consensus is that quantum mechanics is indeed an adequate account of reality. Many consider Bell’s theorem as sufficient proof. See the Wikipedia EPR paradox article. Also referred to as the EPR paradox.
elapsed time. The difference between two moments of time, in contrast to a single moment of time. The amount of time which has passed or passes between two moments of time.
elastic scattering time. TBD.
electric charge. The net electric charge of a particle — the number of protons minus the number of electrons. Synonym for electrical charge.
electric circuit. See electrical circuit or electronic circuit.
electric current. The flow of electric charge in an electric circuit or an electronic circuit. The unit of current being the ampere or coulomb per second. See the Wikipedia Electric current article.
electric field. TBD. See the Wikipedia Electric field article. See also: magnetic field and electromagnetic force.
electric or magnetic field. Either an electric field or a magnetic field, or both — an electromagnetic field. See the Wikipedia Electric field, Magnetic field, and Electromagnetic field articles. Synonym for electrical or magnetic field.
electrical. The subset of electronics related to the use of electrons as a source of power, to power consumer, commercial, and industrial devices, including computers and associated devices. Alternatively, anything involving electrons in any way. See also: electrical device and electrical power.
electrical charge. See electric charge.
electrical circuit. An assembly of electrical components or electronic components and the wiring or other connections among those components.
electrical component. Any hardware component which uses or controls the flow of electrons. See also: electrical device and electronic component.
electrical device. Any device which requires electrons for power — electrical power.
electrical or magnetic field. See electric or magnetic field.
electrical power. The generation or use of electrons to power electrical devices and electronic devices. Shortened as power.
electrical power grid. A network of electrical power plants which produce and deliver electrical power to customers.
electrical power plant. An industrial facility which generates electricity, electrical power for use by its customers.
electrical power source. A supply of electrical power. A battery, electrical outlet, power grid, power plant, generator, solar cell, or any other source capable of supplying a flow of electrons to supply electrical power. Shortened as power source. See also: power supply.
electrical power supply. A device which transforms electrical power from the form delivered by an electrical power source to the form needed by a particular system, such as for the electronic circuits of a computer. See the Wikipedia Power supply article. Shortened as power supply.
electrically neutral. An atom or material, which has a balance of charge or no net charge, making it an insulator, in contrast to a conductor, which is not electrically neutral.
electricity. See electrical power.
electromagnetic field. A combination of an electric field and a magnetic field. See the Wikipedia Electromagnetic field article.
electromagnetic force. See electromagnetism.
electromagnetic radiation (EMR). Energy which is transmitted via photons, having both an electric field and a magnetic field, where the energy of a single photon is proportional to the frequency of the photon, in contrast to matter or particles which have mass, such as electrons. Photons behave according to the principles of quantum mechanics, having both particle and wave qualities, including a wave function. See the Wikipedia Electromagnetic radiation article. Quantum computers may make use of EMR, such as microwaves to control qubits, but generally the primary concern is to shield the quantum computer, the qubits, from stray electromagnetic radiation from the environment which may disrupt the quantum state of the qubits, which is nominally rather fragile and easily disturbed by EMR. Shortened as radiation.
electromagnetic signal. The use of electromagnetism to transmit energy used for either control or data. See electromagnetic radiation (EMR).
electromagnetism. The propagation of photons, such as light, radio waves, microwaves, and other forms of electromagnetic radiation (EMR). See the Wikipedia Electromagnetism article. See also electric field and magnetic field. Synonym for electromagnetic radiation (EMR).
electron. The elementary particle associated with holding and transmitting charge. See the Wikipedia Electron article. See also: electronic, electronic circuit, electrical.
electron−nucleus entanglement. TBD. Referenced in the Universal holonomic quantum gates over geometric spin qubits with polarised microwaves paper by Nagata, Kuramitani, Sekiguchi, and Kosaka.
electronic. Anything related to the flow of electrons, including simply as a source of power, but generally more focused on information and control. See electrical and electronic circuit. See the Wikipedia Electronics article.
electronic circuit. An assembly of electronic components and the wiring or other connections among those components.
electronic circuitry. See electronic circuit. May be shortened as circuitry. See also: digital circuitry.
electronic component. An individual device which facilitates the control of electrons. Used to construct electronic circuits. Includes resistors, capacitors, inductors, diodes, transistors, crystals, switches, antennas, sensors, integrated circuits, vacuum tubes, relays, batteries, lamps, terminals, and connectors. See the Wikipedia Electronic component article. See also: electrical component.
electronic device. Any device which utilizes electronic components. See also: electrical device. Alternatively, synonym for an individual electronic component.
electronic structure. TBD.
electronic structure Hamiltonian. TBD.
element. Either a chemical element or an item in a collection of items, such as an element of a set. Synonym for item.
element name. The name given to a chemical element. See also: chemical symbol. Alternatively, a name, identifier, or label associated with an element which is an item.
element of a set. One of the items which comprise a set.
elementary gate. See elementary quantum gate.
elementary operation. The most basic quantum logic gates into which most [TBD: all?] other gates can be decomposed into as a sequence — the CNOT gate and the U gate (or RZ gate and RY gate).
elementary particle. The subatomic particles which compose matter and hold and transmit electrical current. Most simply, electrons, protons, and neutrons. Photons are also considered elementary particles. At a deeper level, there are hadrons, fermions, leptons, bosons, quarks, and a whole zoo of other elementary particles. See the Wikipedia Elementary particle article.
elementary quantum gate. See elementary operation. [TBD: Need to be more explicit].
embedded domain-specific language. The ability to embed a quantum program or quantum circuit in a high-level language. Technically, this should be for an application domain, rather than targeting a machine language such as for a quantum computer, but the term has been used with respect to quantum computing in the A Practical Quantum Instruction Set Architecture paper by Smith, Curtis, and Zeng of Rigetti Computing. Abbreviated as EDSL. See Language-Integrated Quantum Operations: LIQUi|> from Microsoft.
empty string. A string or sequence of characters which contains no characters.
encoded quantum states. TBD.
encrypt. See encryption.
encrypt a message. See encryption.
encrypt message. See encryption.
encryption. Encoding of cryptographic messages using cryptographic methods. See also: quantum encryption. See the Wikipedia Encryption article.
encryption key. See cryptographic key.
end-user. A person who is not a computer professional or at least not a software developer, typically using application software. The main point is that they are not concerned with what happens inside of the system and certainly not the code or hardware in the system. They simply want to know only the minimum about the computer and software absolutely necessary for them to do their job. They may have a curiosity about further details, but their role as an end-user does not require any such knowledge.
energy. Information and a source of power.
energy level. See quantum energy level.
energy relaxation time. How long a qubit can be expected to remain in the |1> state before decaying to the |0> state. Also known as amplitude coherence time or amplitude damping time. Abbreviated as T1. See also: dephasing time (T2).
enhancement mode quantum dots. Or enhancement quantum dots. Or enhancement QD. TBD. See the Scalable Quantum Computing With “Enhancement” Quantum Dots paper. See also depletion mode quantum dots.
ensemble average fidelity. TBD.
ensemble of pure states. TBD.
ensemble of quantum states. TBD.
ensemble of states. TBD.
entangle. To cause the quantum state of two quantum systems (such as two qubits) to become entangled — the same, a single quantum state.) See quantum entanglement. See also: entangle two qubits.
entangle three qubits. See tripartite entanglement.
entangle two qubits. The process of causing the quantum states of two qubits to become entangled — the same. Commonly by applying a Hadamard gate (H gate) on one of the qubits and then applying a controlled-NOT gate (CNOT gate) on the other qubit using the first qubit after execution of the H gate as the control qubit. See quantum entanglement.
entangled. The quantum states of two qubits are entangled — the same. See quantum entanglement.
entangled particles. Two or more particles whose quantum state has become entangled. See the Wikipedia Quantum entanglement article.
entangled qubits. Two qubits whose quantum states are entangled. See quantum entanglement. Alternatively, one or more pairs of qubits which are connected (entangled.) See connectivity between qubits. Also referred to as pair of qubits or qubit pair.
entangled quantum dots. Quantum entanglement when the qubits are implemented as quantum dots.
entangled signals. TBD.
entangled state. The fact that two quantum systems, such as two qubits, are entangled. Alternatively, the quantum state of two quantum systems, such as two qubits, which are entangled. In contrast to separable state and product state.
entangled system. TBD.
entangled systems. TBD.
entanglement. See quantum entanglement.
entanglement catalysis. TBD.
entanglement detection. See quantum entanglement detection.
entanglement dilution. TBD.
entanglement distillation. TBD.
entanglement distillation and dilution. Either entanglement distillation or entanglement dilution. See also: entanglement transformation.
entanglement distillation protocol. TBD.
entanglement entropy. TBD.
entanglement fidelity. TBD.
entanglement of distillation. TBD.
entanglement of formation. TBD.
entanglement theory. See quantum entanglement.
entanglement transformation. TBD. See also: entanglement dilution and entanglement distillation.
entanglement verification. See entanglement verification procedure.
entanglement verification procedure. See quantum entanglement.
entanglement witness. See quantum entanglement witness.
entity. Any object, system, or phenomenon, real or imaginary, which might be referenced in some way. It may or may not have a type. It may or may not have a name.
entry of a matrix. The value of a column in a row of a matrix.
entry. May be an item of a list or a value in a matrix (entry of a matrix).
environment. All environmental conditions of any significance to an entity.
environmental condition.Condition immediately surrounding and near an entity. May be physical environment or computational environment.
environmentally-induced error. A quantum error due to physical or electromagnetic conditions in the environment around a quantum computer, such as stray electromagnetic radiation or a problem with the refrigeration unit.
epoch. TBD.
EPR. Initialism for Einstein–Podolsky–Rosen paradox.
EPR paradox. See Einstein–Podolsky–Rosen paradox.
EPR pair. See Bell state. The reference to EPR is to suggest that Bell’s theorem does indeed resolve the EPR paradox.
EPR state. TBD. See EPR pair.
equipment. Additional apparatus or hardware required to use or operate a system.
error. An unexpected condition, state, value, or result. Something went wrong. Execution of an operation does not yield a correct or expected result. See quantum error.
error-correcting code. See error-correcting code memory. Abbreviated as ECC.
error-correcting code memory. Memory technology for classical computer systems which utilizes extra bits to detect multiple errors and to even automatically correct many of them. See the Wikipedia ECC memory article. Quantum error correction codes (QECC) is the equivalent in quantum computing. Abbreviated as ECC memory or even simply ECC.
error correction. See quantum error correction.
error correction scheme. An approach or method for error correction. Such as using extra bits and redundancy.
error-correction code. See quantum error-correction code.
error-correction scheme. See quantum error-correction scheme.
error detection. Ability to detect errors. Commonly requires some sort of redundancy and comparison.
error mitigated variational relaxation. TBD.
error mitigation. See quantum error mitigation.
error mitigation in quantum simulation. Need to perform error mitigation when using quantum computing to simulate complex physical systems, such as chemistry simulation.
error mitigation scheme. See quantum error mitigation scheme.
error mitigation strategy. See error-mitigation strategy.
error-mitigation strategy. TBD.
error mitigation technique. See quantum error mitigation technique.
error operation. TBD.
error rate. See quantum error rate.
error twirling. TBD. See also: Pauli twirling.
Euler’s number. Mathematical constant which has applications in mathematics and physics, especially quantum mechanics. See the Wikipedia e (mathematical constant) article. Symbolized as e.
Euler’s totient function. The count of positive integers from 1 up to a specified number which are relatively prime to that number, meaning that the greatest common divisor (GCD) of each integer and the specified number is 1. The integers which meet the criterion to be counted are known as totatives. Commonly written as phi(n), where phi is the Greek symbol for phi. See the Wikipedia Euler’s totient function article.
evaluate. Perform an evaluation.
evaluation. The process of considering a technology, product, service, or proposal. May include experimentation and testing. Alternatively, to execute an expression or code, to obtain results. Either way, also includes a review of the results.
event. A relatively discrete change in the state of a system. A change that is detectable or noticeable even if not especially significant or noteworthy. Alternatively, a sequence of changes or smaller events, possibly over an extended period of time, but still having a relatively discrete nature, at least at a higher level, which are noteworthy as a unit at the semantic level, at least for a human observer. See also: activity.
evolution. The process of changing or advancing over time, sometimes incrementally and sometimes by more dramatic leaps. A system evolves over time as its state changes as time progresses.
evolution in quantum computing. An approach to incrementally searching for solutions to a problem based on evolution, inspired by natural evolution (selection.) Genetic programming (GP) on quantum computers. See also: evolutionary algorithm (EA). May be intended as a reference to evolution of quantum computing.
evolution of quantum computing. The stages of advancement of quantum computing, sometimes by leaps and bound, but commonly by slower, incremental improvements. Frequently referred to as generations. Alternatively, a reference to evolution in quantum computing or genetic programming (GP) on quantum computers.
evolutionary algorithm. An algorithm which uses mutation and a fitness function to search for solutions to a problem. Inspired by biological evolution and natural selection. See also: genetic algorithm (GA). See the Wikipedia Evolutionary algorithm article.
evolve. To change or advance over time, sometimes incrementally and sometimes by more dramatic leaps. See evolution.
Ewinization. The use of a quantum-inspired classical algorithm to achieve a speed-up over a classical algorithm to the point where a quantum algorithm no longer has a true and substantial exponential speedup compared to the quantum-inspired classical algorithm. Name is a reference to Ewin Tang, author of the A quantum-inspired classical algorithm for recommendation systems paper.
ex situ optimization. TBD.
exact method. An approach to a problem for which an exact method is known and is not too difficult for a particular computer to solve, in contrast to a hard problem for which only an approximate method is appropriate, even for a quantum computer. See Approximation Methods in QM.
exact QFT. Abbreviation and initialism for exact quantum Fourier transform.
exact quantum Fourier transform. Synonym for full quantum Fourier transform, in contrast to an approximate quantum Fourier transform. Abbreviated as exact QFT.
exact solution. Solution when an exact method is used to solve a problem. Synonym for absolutely precise solution. See also: approximate solution, optimal solution, practical solution
excited state. The various quantum energy levels above the ground state of a quantum system, in contrast to the ground state. In a qubit there is one excited state which represents the basis state |1>, while the ground state represents the basis state |0>. [TBD: verify] See the Wikipedia Excited state article.
exclusion principle. See Pauli exclusion principle.
executable code. Code that is in a format (code format) which can be directly executed. See also: executable code format. See also: intermediate representation. Synonym for binary code. See also: executable program.
executable code format. The data format (code format) which is required for a computer program to be executed on a computer. Commonly output by a programming language compiler. See also: intermediate representation and executable program.
executable program. A computer program which is in a form ready for execution on a computer, such as having been compiled by a compiler from source code.
executable statement. A statement in a high-level programming language which will perform some action when the program is executing, in contrast to a non-executable statement, such a declaration.
execute a quantum algorithm. Technically, the user must code the algorithm in the form of a quantum program or quantum circuit, which can then be executed. See execute a quantum program or execute a quantum circuit.
execute a quantum circuit. See quantum logic circuit execution.
execute a quantum program. See quantum program execution.
executing a quantum logic circuit. See quantum logic circuit execution.
execution. May be either quantum logic circuit execution or quantum program execution, which are the same in most contexts. Alternatively, reference to execution of a classical program.
execution phase. The stage of processing of a quantum program or quantum circuit in which the quantum logic gates are actually acting on the qubits of a quantum computer. See quantum circuit execution or quantum program execution. See also: preparation phase, measurement phase, and post-processing phase.
exhaustive enumeration. A simple approach to any problem which is based on incrementally trying all possible solutions rather than focusing in a directed manner towards a solution such as by directly evaluating a formula or using heuristics. Synonym for brute force.
exhaustive search. See brute-force search.
exhibit quantum properties. The effects of the portions of a quantum computer in which the principles of quantum mechanics, primarily superposition and entanglement, are being exploited by the quantum logic gates of a quantum program or a quantum logic circuit. The effects or properties cannot be observed directly at the moment they are occurring without disturbing the quantum state, but they can be measured once the computation has completed.
existing general purpose quantum computer. See current general purpose quantum computer.
existing quantum computer. See current quantum computer.
expectation value. TBD. See the Wikipedia Expectation value (quantum mechanics) article.
expected result. The result which is wanted, in contrast to the result which actually occurred. See also: actual result, desired result, and expected outcome.
expected outcome. A possible outcome from the perspective of a user or program. See also: prediction, theory, and expected result.
experiment. A user performs a test, to learn about a new technology or a new situation. Alternatively, a demonstration, to show the capabilities of a technology. Alternatively, an algorithm which performs automated tests to evaluate alternative solutions. See also demonstration. Alternatively, a test performed by a researcher to validate a theory, to gain insight, or to collect data relating to some phenomenon. An experiment may require hardware, software, equipment, or other apparatus.
experimental problem. A problem which is of experimental or speculative interest to an organization or individual, in contrast to a theoretical problem, a research problem, or a practical problem.
experimental quantum computing. Performing experiments in the context of quantum computing. Alternatively, the development of quantum computers which are only stepping stones to an eventual, practical quantum computer, each quantum computer along the way designed to both demonstrate capabilities and to yield insights to facilitate evolution of the design of the next stage of quantum computing.
experimental stage. The stage of development of a technology where the research stage has been completed, but experimentation and testing of the technology are needed before proceeding to the product development stage and then on to the commercial availability stage. The goal is to gain knowledge and insight, and to validate whether the technology actually works as expected.
experimentation. The process of learning about a technology, product, service, or system through experiments. The goal is to gain knowledge and insight, and to validate whether the technology actually works as expected. See also: experimental stage.
experimenting. See experimentation.
exponential. See exponential time and exponentially.
exponential complexity. See exponential time.
exponential rate. See exponential time.
exponential speedup. The performance benefit from an algorithm which has only polynomial complexity compared to an algorithm with exponential complexity.
exponential time. An algorithm whose cost or complexity grows exponentially as its input grows, in contrast to polynomial time. See the Wikipedia Time complexity article.
exponentially. A relatively small number raised to the nth power, in contrast to polynomially — n raised to a relatively small number. It grows much faster, which is bad, which is the hallmark of a classical computer and why a quantum computer is superior.
exponentially hard. See exponentially hard problem.
exponentially hard problem. A problem or computation where the time to complete the computation rises exponentially with the size of the input. In contrast to polynomial time. For example, O(2^n) vs. O(n²). These are the problems for which quantum computers are thought to be more appropriate than classical computers.
express. Represent an idea, concept, intention, or other entity in some form, such as in natural language, pictures and diagrams, or some specialized language or specialized notation. See also: conceptualize, theorize, and formulate.
expression. A notation in a high-level programming language which permits the programmer to express a potentially complex mathematical formula in a reasonably concise manner. A compiler or interpreter will then translate this compact notation into a sequence of machine language instructions. Expressions are generally used within statements which are in turn collected into a program. Alternatively, anything which can be expressed in a language defined by a grammar, which could be either a programming language, a specialized language, or even natural language.
extended Clifford operation. TBD. Referenced in the Classical simulation complexity of extended Clifford circuits paper by Jozsa and Van den Nest.
extended-precision floating point. Representation of a real value in 80 bits on a classical computer. Covers values of magnitude from approximately 3.65 times 10 to the minus 4,951 to approximately 1.18 times 10 to the 4,932. See the Wikipedia Extended precision article. See also: single-precision floating point and double-precision floating point.
extensible markup language. A data format for semi-structured information. Abbreviated as XML or XML data format. See the wikipedia XML article.
extremum of an objective function. Either the minimum or the maximum of a function (the objective function) over which an activity is to be optimized.
fabric. Synonym for grid or lattice. May emphasize that the devices are in the grid or that they are on the edges of the grid, with the interconnections between devices comprising the grid (fabric) itself.
fabric of programmable elements. See fabric of quantum devices. Alternatively, the devices may be digital devices.
fabric of quantum devices. See integrated fabric of programmable quantum devices.
fabricate. See fabrication. To produce chips. Alternatively, to build systems.
fabrication. The process of producing chips (integrated circuits). Alternatively, the process of building systems.
factoring integers. TBD. Referenced in the Polynomial-Time Algorithms for Prime Factorization and Discrete Logarithms on a Quantum Computer paper by Shor. See also: finding discrete logarithms.
factoring integers and finding discrete logarithms. TBD. Referenced in the Polynomial-Time Algorithms for Prime Factorization and Discrete Logarithms on a Quantum Computer paper by Shor.
falsify. Test and confirm whether a proposition or theory is false. See also: falsify a theory. See the Wikipedia Falsifiability article.
falsify a theory. Propose and perform experiments which have the prospect of proving that a theory is false. See also: validate a theory.
family of machine architectures. Two or more machine architectures may be somewhat similar although not identical and share enough noteworthy similarities to be considered a family. For example, they may have nearly 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 otherwise identical.
famous quantum algorithms. Quantum algorithms which are especially noteworthy, especially from a historical perspective. Such as Grover’s algorithm and Shor’s algorithm.
Faraday cage. A metallic mesh enclosure for a device, such as a quantum computer, which blocks most if not almost all stray electromagnetic radiation which might interfere with the operation of the device. See also: Faraday shield. See the Wikipedia Faraday cage article.
Faraday shield. A metallic sheet enclosure for a device, such as a quantum computer or subsystem of a quantum computer, which blocks virtually all stray electromagnetic radiation which might interfere with the operation of the device. See also: Faraday cage. Alternatively, the term Faraday shield may be loosely used to refer to all forms of shielding, including a Faraday cage. See the Wikipedia Faraday cage article.
fast and fault-tolerant manipulation. TBD. Referenced in the Universal holonomic quantum gates over geometric spin qubits with polarised microwaves paper by Nagata, Kuramitani, Sekiguchi, and Kosaka.
fast Fourier transform. TBD. See the Wikipedia Fast Fourier transform article. Abbreviated as FFT.
fault-tolerance. See fault tolerance.
fault tolerance. Ability to detect errors or component failures and correct or mitigate them so that normal operation can continue as if no error had occurred. See also: error detection, error correction, and error mitigation. See the Wikipedia Fault tolerance article.
fault-tolerant. See fault tolerance.
fault tolerant. See fault tolerance.
fault-tolerant holonomic quantum computing. TBD. Referenced in the Universal holonomic quantum gates over geometric spin qubits with polarised microwaves paper by Nagata, Kuramitani, Sekiguchi, and Kosaka.
fault-tolerant quantum computation. Adding qubits or executing the same computation multiple times (or many times) to compensate for the fact that quantum errors may occur during the computation.
fault-tolerant quantum computer. TBD. See also: fault-tolerant quantum computation. Abbreviated as FTQC.
fault-tolerant universal quantum computer. TBD. Referenced in the Universal holonomic quantum gates over geometric spin qubits with polarised microwaves paper by Nagata, Kuramitani, Sekiguchi, and Kosaka.
faults. See quantum faults.
faulty gate. See faulty quantum logic gate.
faulty gate operation. See faulty gate.
faulty measurement. See faulty quantum measurement.
faulty preparation. See faulty quantum preparation.
faulty quantum gate. See faulty quantum logic gate.
faulty quantum gate operation. See faulty quantum gate.
faulty quantum logic gate. A quantum logic gate for which a quantum error has occurred during its execution. This is not to say that there is anything wrong with the gate per se, but simply that the error occurred at the same time as the execution of the gate.
faulty quantum measurement. A quantum error has occurred during quantum measurement, the quantum logic gates use to measure the quantum state of the qubits. This is not to say that there is anything wrong with a measurement logic gate per se, but simply that the error occurred at the same time as execution of a gate during measurement.
faulty quantum preparation. A quantum error has occurred during quantum preparation, the quantum logic gates use to initialize the quantum state of the qubits. This is not to say that there is anything wrong with the preparation per se, but simply that the error occurred at the same time as the execution of a gate during preparation.
feature. A quality, capability, or function of a system or device, including hardware, computing systems, computer programs, and other software. See also: function and capability.
feedback. See feedback loop.
feedback loop. The ability of the results of a process or computation to be used as a future input into that same process or computation, an arbitrary number of times.
Fermi-Dirac statistics. See fermion. TBD. Beyond the scope of this glossary, for now. See the Wikipedia Fermi–Dirac statistics article.
Fermi-Hubbard model. TBD. Abbreviated as FHM.
fermion. Any particle which obeys Fermi-Dirac statistics. Commonly electrons, protons, and neutrons. See also: photon and boson. See the Wikipedia Fermion article.
fermionic ansatz. TBD.
fermionic fast Fourier transform. TBD. Abbreviated as FFFT.
fermionic gaussian transformation. TBD.
fermionic quantum simulation. TBD.
fermionic simulation. TBD. Abbreviated as fSim.
fermionic system. TBD. See also: strongly correlated fermionic systems and weakly correlated fermionic systems.
FFFT. Initialism for fermionic fast Fourier transform.
FFT. Initialism for fast Fourier transform.
FHM. Initialism for Fermi-Hubbard model.
fiber. See optical fiber cable.
fiber cable. See optical fiber cable.
fiber optic cable. See optical fiber cable.
fidelity. See quantum logic circuit fidelity. See also: coherence, decoherence.
fidelity-based geometric measure of coherence. TBD.
field of quantum computing. Everything relating to quantum computers, including theory, architecture, design, construction, deployment, operation, use, algorithms, programming, applications, economics, business and social implications, public policy, etc.
figure of merit. A quantity used to characterize some quality of a system, such as its capacity or performance. At present, the only figures of merit for quantum computers are their number of qubits and their decoherence time or quantum error rate. See the Wikipedia Figure of merit article.
final format. The data format for which no further transformation is required before processing (such as execution), in contrast to a source format or intermediate format. See also: intermediate representation.
final results. The measured state of a quantum computer at the end of execution of a quantum program or circuit, which will be returned to the host program or user which requested the execution of the quantum program or circuit.
final state. The state of a system at the completion of processing.
final value. The value of a variable at the completion of processing.
finding discrete logarithms. TBD. Referenced in the Polynomial-Time Algorithms for Prime Factorization and Discrete Logarithms on a Quantum Computer paper by Shor. See also: factoring integers.
finite measurement statistics. TBD.
finite-state automaton. See finite-state machine. Shortened as FSA. see also quantum finite-state automaton.
finite-state machine. An automaton or state machine. See the Wikipedia Finite-state machine article. Shortened as FSM. See also: quantum finite-state machine.
firmware. Specialized software used to program specialized processors which are embedded within devices and even in a computer, but distinct from the main processor of a computer system. Technically, there may be firmware embedded within the main processor as well, called microcode, but that is distinct from software which is executed by the main processor.
first introduction to quantum computing. Any introductory narrative for users who have not been exposed to quantum computing previously. Here’s an appropriately titled book, although I can make no claims about it: A First Introduction to Quantum Computing and Information by Bernard Zygelman. There’s only one catch — it’s not due until September 15, 2018. The bottom line at this stage of the evolution of quantum computing is that there really isn’t any decent first introduction to quantum computing available. For now, I’m afraid, one of the best starting points is simply the Wikipedia Quantum computing article. And this short article from IBM, Introduction to Quantum Computing. And this reasonably decent tutorial from Emma Strubell, Introduction to Quantum Computing — Part I, and Part II. And for those a bit more ambitious, Lecture 19: How to Build Your Own Quantum Computer from Peter Shor’s lecture notes on Quantum computation.
fixed capacitive coupling. TBD. See also: capacitive coupling.
fixed coupling device. TBD.
fixed frequency. A frequency which is constant, such as for a photon or microwave pulse, in contrast to a tunable frequency, which can vary. See also: resonator and resonant frequency.
fixed-frequency qubit. A qubit whose frequency is fixed and cannot vary, in contrast to a tunable qubit. Generally refers to the resonators used to control and couple qubits rather than the qubit itself.
fixed-frequency superconducting transmon qubit. The specific qubit technology used by IBM Q as of July 2018.
fixed-frequency transmon. See fixed-frequency superconducting transmon qubit.
fixed-function quantum computer. A quantum computer which is tailored to only one narrow niche class of problems, in contrast to a universal quantum computer or general purpose quantum computer, which can be applied to all classes of problems. Synonym for fixed-purpose quantum computer.
fixed-function system. See fixed-function quantum computer.
fixed-length list. See list. In contrast to a dynamic list which can change in length.
fixed-purpose. See fixed purpose.
fixed purpose. Suitable only for a very specific type of purpose, such as a single algorithm or a very narrow class of algorithms, in contrast to the somewhat wider range of uses of narrow purpose, or the wide range of uses of general purpose.
fixed-purpose quantum computer. See fixed-function quantum computer.
fixed universal state. TBD.
flash memory. The use of integrated circuits for persistent storage of data. See the Wikipedia Flash memory article. See also: solid-state storage and solid-state drive.
flash storage. See solid-state storage and flash memory.
flip. See flip a qubit.
flip a bit. Complement a bit. On a classical computer, complement a binary bit. A 0 becomes a 1 and a 1 becomes a 0. On a quantum computer, see flip a qubit.
flip operation. Any quantum logic gate which reverses the quantum state of a qubit. See flip a qubit.
flip a qubit. Reverse the quantum state of a qubit, changing |1> to |0> and |0> to |1>. Usually via execution of a CNOT operation. Alternatively, flip the phase of a qubit.
flip error. Quantum error which occurs during execution of a flip operation. See also: phase flip error.
floating-point number. A representation for a real number on a classical number. See single precision floating point, double-precision floating point, and extended-precision floating point. No relevance to a quantum computer at this stage.
floating-point value. See floating-point number.
flow of current. See flow of electrons.
flow of electrons. The transmission of electrons, typically via a conductor.The use of electrons to power and control electrical and electronic devices. See also: connections and wiring.
flux bias line. TBD. Use of radio frequency (RF) signals to control a qubit, such as for execution of a quantum logic gate. See also: RF drive and microwave drive. Referenced in The Quantum Processing Unit (QPU) doc from Rigetti Computing.
flux bias settling tails. TBD.
flux bias wiring. TBD.
flux control pulse. TBD.
flux quantum computing. A quantum computer project and community sponsored by the Department of Electrical and Computer Engineering at Stony Brook University. Their website is Quantarctic.
flux qubit. A qubit based on a superconducting loop containing Josephson junctions and using microwave pulses to manipulate the quantum state of the qubit. See the Wikipedia Flux qubit article. Other types of qubit include charge qubit, phase qubit, and spin qubit. See also: flux-tunable qubit.
flux settling tails. TBD.
flux-tunable qubit. A flux qubit which uses a tunable frequency, in contrast to a fixed frequency. Some quantum computers pair the two for coupling (entanglement).
flying qubit. Qubit which is mobile and can be transported between locations, maintaining its quantum state, in contrast to a stationary qubit. Referenced in the Universal holonomic quantum gates over geometric spin qubits with polarised microwaves paper by Nagata, Kuramitani, Sekiguchi, and Kosaka. See the Flying qubits make for a highly resilient quantum memory article.
Fock state. TBD. See the Analytical modeling of parametrically-modulated transmon qubits paper by Didier, Sete, da Silva, Rigetti. See also: parametrically-activated entangling gates.
force. The ability to cause an effect. See the Wikipedia Force article.
format. See data format.
formula. Solution to a problem which requires only a relatively simple mathematical calculation, in the form of an algebraic expression, in contrast to a brute-force algorithm or a heuristic.
formulate. Flesh out and express a concept or approach.
Forrelation. TBD. See the “Forrelation: A Problem that Optimally Separates Quantum from Classical Computing” paper by Aaronson and Ambainis.
four-qubit cat state. TBD.
four maximally entangled two-qubit states. TBD. see also: maximally entangled two-qubit states.
four mutually orthogonal entangled states. TBD. see also: mutually orthogonal entangled states.
Fourier space. TBD. Referenced in the Circuit for Shor’s algorithm using 2n+3 qubits paper by Beauregard.
Fourier transform. TBD. See the Wikipedia Fourier transform article. See also: discrete Fourier transform and quantum Fourier transform.
fraction. A number represented as a numerator and a denominator, both of which are integers. Alternatively, the non-integer portion of a real number — the fractional digits, the digits to the right of the decimal point. Alternatively, the fractional digits of a real number. Alternatively, whether the fractional digits are non-zero, as in whether a number has a fraction, whether it needs fractional digits to accurately represent its value.
fractional digits. The digits to the right of the decimal point of a real number. The non-integer portion of a real number.
fractional part. See fractional digits.
framework. See software framework.
Fredkin (CSWAP) gate. A 3-qubit gate which conditionally swaps the second and third qubits based on the quantum state of the first qubit. See the Wikipedia Quantum logic gate article.
free fermion evolution. TBD.
free fermion wavefunction. TBD.
frequency. How often an event occurs or completes a cycle. Such as electromagnetic radiation, whose frequency is measured in cycles per second, called hertz. See the Wikipedia Frequency article.
frequency tunability. The range of frequency over which a device can be tuned.
frequency-tunable qubit. Generally refers to the resonators used to control and couple qubits rather than the qubit itself. See the Tunable Superconducting Qubits with Flux-Independent Coherence paper from Hutchings, Hertzberg, Liu, Bronn, Keefe, Chow, and Plourde. Shortened as tunable qubit. See also: fixed-frequency qubit.
frequency-tuned qubit. See frequency-tunable qubit.
front-end server. A server (computer system) placed between another computer system and a network so that users on the network will communicate indirectly to that other system by directly communicating through the front-end server. A useful configuration for making a quantum computer available on a network.
FSA. Initialism for finite-state automaton.
fSim. Abbreviation for fermionic simulation.
fSim gate. Quantum logic gate useful for fermionic simulation. Actually, a family or range of quantum logic gates useful for fermionic simulation.
fSim gate set. A family or range of quantum logic gates useful for fermionic simulation. See the Demonstrating a Continuous Set of Two-qubit Gates for Near-term Quantum Algorithms paper by Foxen, et al.
FSM. Initialism for finite-state machine.
FTQC. Initialism for fault-tolerant quantum computer.
full convex coherence monotone. TBD.
full error correction. The degree of quantum error correction which assures that all of the most common quantum errors will be both detected and mitigated. This requires a significant number of additional qubits. No computer is perfect, but this will be as good as any classical computer.
full quantum Fourier transform. A quantum Fourier transform in which all transform entries participate in the computation, in contrast to an approximate quantum Fourier transform, such as a banded quantum Fourier transform, which discards smaller entries in favor of far fewer gates and much better performance. Synonym for regular quantum Fourier transform and exact quantum Fourier transform.
full stack. All levels or layers of software. Depending on context, may or may not include operating system, system utilities, development tools, and basic software tools. Depending on context, may include hardware as well. See also: full-stack quantum.
full-stack quantum. An approach, effort, or organization which addresses all levels of quantum computing, from the lower levels of hardware, including the physics and chip design, to the upper levels of software, including tools and applications, in contrast to a focus on a subset of those levels. See also: quantum stack.
fully connected. See fully entangled.
fully-connected. See fully entangled.
fully-connected quantum computer. A quantum computer whose qubits are fully connected — any qubit can be entangled with any other qubit, in contrast with only limited pairs of qubits.
fully entangled. All possible pairs of qubits of a quantum computer may be entangled simultaneously, in contrast with partially entangled or minimally entangled, where only some pairs of qubits may be entangled at the same time. [TBD: verify]. For reference, see the 16-qubit IBM universal quantum computer can be fully entangled paper.
fully-entangled. See fully entangled.
fully functional. A technology, system, prototype, product, or service which is able to perform all functions which are expected of it.
function. An algorithm or block of code which can be invoked by its name and with arguments or values to perform some computation, commonly a mathematical function, returning some result. Alternatively, the purpose or effect of something, regardless of how that effect is achieved. See also: feature.
function argument. The value or expression which will evaluate to a value to be supplied to a function for a function parameter on a function call in code. May be abbreviated to argument
function call. Invocation of a function, giving its name and values or expressions for any arguments (parameters) which it may require.
function parameter. A named quantity representing a value which a function requires to be supplied on a function call in code in order to perform the logic of the function. Any number of parameters can be required. May be abbreviated as parameter.
functional. Relating to function. Alternatively, actually able to function, to perform at least some fraction of the functions which are expected. See also: fully functional.
functional spec. Abbreviation for functional specification.
functional specification. A document which records the result of designing the externally visible function of a system. Details all aspects of what the user will see. If the system has an API, the details of the API will be described, fully, or detailed in a separate API specification. See also: detailed specification, architecture specification, API specification, requirements specification, and design specification. For a hardware system, such as a computer, a principles of operation document would be the equivalent of a functional specification.
future quantum computer. A quantum computer which does not exist today but might become available in the future, possibly the near future, but possibly the more distant future, or at least significantly beyond the very near-term, in contrast with current quantum computer, which is available today, or near-term quantum computer, which is likely to become available in the relatively near future, the next few months or maybe within a year or so.
GA. Initialism for genetic algorithm.
gadgetization. TBD.
gas. Matter which expands and contracts freely in addition to flowing freely in all directions. See also: solid, liquid, and plasma.
gaseous. Having the quality of a gas.
gaseous matter. Matter in the form of a gas. See also: solid matter, liquid matter, and plasma matter.
gaseous medium. A medium comprised of gas, in contrast with solid medium, liquid medium, or plasma medium. See also: gaseous matter.
gate. See quantum logic gate. The quantum equivalent of an instruction or operation on a classical computer. Not the same as a hardware gate in classical computing.
gate-based local operations. TBD.
gate-based quantum computer. A quantum computer which supports gate-based quantum computing — quantum programs constructed as quantum logic circuits using quantum logic gates. In contrast to a fixed-function quantum computer.
gate-based quantum computing. Quantum computing based on quantum logic circuits (quantum programs) constructed using quantum logic gates. In contrast to computing on a fixed-function quantum computer.
gate compression. A situation where a sequence of quantum logic gates can be optimized of combined (compressed) into a single gate.
gate count. The number of quantum logic gates in a quantum logic circuit. Synonym for quantum logic gate count, quantum logic circuit depth, or circuit depth.
gate duration. TBD. [Same as gate length?]
gate error. See quantum logic gate error.
gate execution. See quantum logic gate execution.
gate fidelity. TBD.
gate interval. TBD. [Same as gate length or gate duration?]
gate leakage error. TBD.
gate length. Duration of execution of a single quantum logic gate. Width of the pulse needed to perform the function of the gate. Typically in nanoseconds.
gate sequence. Synonym for circuit. See quantum logic circuit. Also referred to as quantum gate sequence, quantum circuit, or quantum logic gate sequence. Equivalent to a sequence of instructions or a sequence of operations on a classical computer.
gate set. See quantum gate set.
gate set tomography. See quantum gate set tomography. Abbreviated as GST.
gate time. TBD.
gate transformation. TBD. Referenced in the Universal holonomic quantum gates over geometric spin qubits with polarised microwaves paper by Nagata, Kuramitani, Sekiguchi, and Kosaka.
general computing. See general-purpose computing.
general measurement. TBD. See also: projective measurement.
general theory of quantum entanglement. TBD.
general-purpose. See general purpose.
general purpose. Suitable for a wide range of uses, in contrast to fixed-purpose or narrow purpose.
general purpose computer. See general-purpose computer.
general-purpose computer. A computer designed for a wide range or even unlimited purposes, in contrast to a specialized computer.
general-purpose computing. See general-purpose computer.
general-purpose programming language. A programming language which applies to most if not all types of applications, in contrast to a specialized programming language which applies to a subset of applications, or even a niche application, such as data science or statistics.
general purpose quantum computer. See general-purpose quantum computer.
general-purpose quantum computer. A quantum computer which has sufficient capabilities to usefully apply to a wide range of practical, real-world problems, in contrast to a fixed-function quantum computer which only applies to a narrow niche of problems. May simply be a synonym for large-scale quantum computer. It may or may not be a true universal quantum computer, able to compute whatever a classical computer can compute, but it does need to apply to a fairly wide range of problems even if it can’t replicate all functions of a classical computer. It will also need a large enough number of qubits, a reasonably long coherence, and some significant degree of quantum error correction. Even then, there may still be applications which can be executed on a classical computer but are still not able to execute on any existing general purpose quantum computer, such as those processing large volumes of semi-structured data or running complex software systems. See also: current general purpose quantum computer.
general-purpose quantum computing. Computing capable on a general-purpose quantum computer.
general purpose quantum processor. The core processor (quantum computer processor) of a quantum computer, where the qubits are located and where quantum computation actually occurs, and emphasizing that this is a general purpose quantum computer, in contrast to a fixed-purpose quantum computer or having only a rather limited capacity. Generally a synonym for general purpose quantum computer as well.
general purpose superconducting quantum processor. See general purpose quantum processor. At present, and for the foreseeable future, all of them are of necessity superconducting. See also: quantum processor.
general purpose, universal quantum computer. See general-purpose, universal quantum computer.
general-purpose, universal quantum computer. Technically, this is redundant — see general-purpose quantum computer. If a quantum computer does not have a universal set of operations, it is not going to be general purpose.
general quantum computer. See general purpose quantum computer. May also simply be a universal quantum computer, but lack sufficient capabilities to be truly general purpose.
general quantum programs. Arbitrary quantum programs, of arbitrary complexity, and arbitrary length, without restriction.
generalized pure-state N-representability conditions. TBD.
generation of a graphical image. See graphical image generation. Also referred to as rendering a graphical image for display.
generative task. TBD.
generic quantum circuit. Any arbitrary quantum logic circuit, of arbitrary complexity, and arbitrary length, without restriction. Synonym for general quantum program. Alternatively a single quantum circuit which is capable of solving a broad class of problems.
genetic algorithm. One form of evolutionary algorithm (EA) using natural selection to search for solutions to a problem. See the Wikipedia Genetic algorithm article. Abbreviated as GA.
genetic programming. See genetic algorithm (GA) and evolutionary algorithm (EA). Abbreviated as GP. See the Wikipedia Genetic programming article.
geometric entangled states. TBD. Referenced in the Universal holonomic quantum gates over geometric spin qubits with polarised microwaves paper by Nagata, Kuramitani, Sekiguchi, and Kosaka.
geometric measure of coherence. TBD.
geometric phase gate. TBD. Referenced in the Universal holonomic quantum gates over geometric spin qubits with polarised microwaves paper by Nagata, Kuramitani, Sekiguchi, and Kosaka.
geometric phase space. TBD. Referenced in the Universal holonomic quantum gates over geometric spin qubits with polarised microwaves paper by Nagata, Kuramitani, Sekiguchi, and Kosaka.
geometric spin qubit. TBD. Referenced in the Universal holonomic quantum gates over geometric spin qubits with polarised microwaves paper by Nagata, Kuramitani, Sekiguchi, and Kosaka.
geometric spin state measurement. TBD. Referenced in the Universal holonomic quantum gates over geometric spin qubits with polarised microwaves paper by Nagata, Kuramitani, Sekiguchi, and Kosaka.
geometric spin state preparation. TBD. Referenced in the Universal holonomic quantum gates over geometric spin qubits with polarised microwaves paper by Nagata, Kuramitani, Sekiguchi, and Kosaka.
geometric spin state preparation and measurement. TBD. Referenced in the Universal holonomic quantum gates over geometric spin qubits with polarised microwaves paper by Nagata, Kuramitani, Sekiguchi, and Kosaka.
GHZ. See GHZ state. Initialism for Greenberger-Horne-Zeilinger. Not to be confused with GHz, which is the abbreviation for gigahertz, a unit of frequency.
GHZ state. Short for Greenberger–Horne–Zeilinger state.
Givens rotation. TBD.
Givens rotation error. TBD.
Givens rotation gate. TBD.
global phase factor. TBD. See also: up to a global phase factor.
global property. TBD.
gmon qubit. TBD.
GP. Initialism for genetic programming.
GPU. Initialism for graphics processing unit.
gradient-based optimization of quantum circuits. TBD.
gradient descent. TBD.
grammar. A set of syntax rules which define a language, and which can be transformed into a state machine which will recognize expressions in that language. See also: quantum grammar. See the Wikipedia Backus–Naur form article.
graph. Either a visual presentation of data or a representation of data according to graph theory of relationships between the data as nodes and edges. See also: tree, directed graph, and undirected graph.
graph theory. A mathematical framework for organizing data or information based on relationships, with nodes for data and edges for relationships between the data represented by the nodes. See the Wikipedia Graph theory article. See also: tree and network.
graphic. See graphical.
graphical. Having a visual or spatial quality, associated with an image, in contrast to a numeric, textual, or symbolic quality.
graphical element. See graphical image element.
graphical hardware. Hardware which is specialized for working with graphical images, including rendering graphical images for display (graphical image generation.) See also: graphical software and graphical processing unit (GPU).
graphical image. An image generated by graphical software or graphical hardware on a computer, typically for display. Could technically be a photographic image as well or include elements of photographic images, but the emphasis is on graphical elements generated by the computer. Conceptually, graphical images could be three-dimensional as well as two-dimensional. See also: graphical video.
graphical image effect. A graphical image operation or graphical image transformation designed to have a visual impact on the graphical image, as a whole or portions or individual graphical image elements or selective graphical image element groups.
graphical image element. Any element used to construct a graphical image, including points, lines, geometric figures, arbitrary curves, freehand drawing, color, shading, fading, gradients, layering, patterns, portions of photographic images or other graphical images, text and text properties, as well as graphical image effects and graphical image transformations on the graphical image elements, individually or as selective graphical image element groups, or on the whole graphical image or designated portions.
graphical image element group. A collection of graphical image elements to be treated collectively rather than individually. Equivalent to the individual graphical image elements, but possibly used either merely for convenience, to reuse a pattern of graphical image elements, or to repeat the pattern.
graphical image generation. Combining any number of graphical elements into a single image, using graphical software and possibly graphical hardware. Synonym for generation of a graphical image. Potential for acceleration by a quantum computer.
graphical image processing. The reverse of graphical image generation — attempting to deduce the graphical image elements which are either present intact in the graphical image or were conceivably used to generate the image. This would include object detection and recognition, feature extraction, and text extraction, among other possibilities. Similar processing could occur for the associated audio — detecting and recognizing voices, speech, music, sounds, background noise, background voices, etc., including detection of synchronization between image and audio elements. Alternatively, any additional processing of the graphical image, including sizing, compression, data format conversion, etc.
graphical image rendering. See graphical image generation.
graphical image transformation. A transformation of a graphical image or one or more graphical image elements or graphical image element groups, such as shifting, sizing, rotation, cropping, mirroring, reversing colors, mapping colors, and more complex graphical operations, operating on the graphical image as a whole or portions or individual graphical image elements or selective graphical image element groups. Potential for acceleration by a quantum computer.
graphical operation. Any operation performed on a graphical image, a portion of the image, or one or more graphical image elements or graphical image element groups. Potential for acceleration by a quantum computer. See also: graphical image transformation and graphical image effect.
graphical software. Software which is specialized for working with graphical images, including rendering graphical images for display (graphical image generation.) See also: graphical hardware. Potential for acceleration by a quantum computer.
graphical symbol. A symbolic mark which is not a character.
graphical video. Digital video produced by graphical video generation. See also: graphical image.
graphical video generation. Generation of digital video based on graphical images, plus audio from some other source. Potential for acceleration by a quantum computer.
graphics processing unit. A processor chip which specializes in the operations needed to render graphical images for display, but which is also quite useful for fast, parallel non-graphics computation. Abbreviated as GPU.
graphics processor. See graphics processing unit.
Greenberger-Horne-Zeilinger. See Greenberger-Horne-Zeilinger state. Abbreviated as GHZ.
Greenberger-Horne-Zeilinger state. Three or more qubits which are entangled with the same quantum state, such as (|000> + |111>)/sqrt(2). See the Wikipedia Greenberger–Horne–Zeilinger state article. See also: W state and multipartite entanglement.
grid. Entities organized in a regular, rectangular pattern. May be computer systems, storage devices, or portions of an integrated circuit. See lattice. Alternatively, a geographically dispersed collection of systems, whether computer systems or electrical power plants, which are interconnected, but not necessarily in a regular, rectangular arrangement. See also: amorphous and fabric.
grid-like structure. See grid, but not necessarily strictly regular. See also: amorphous.
ground state. Lowest energy state of a quantum system, in contrast to an excited state. In a qubit this would be the representation of |0>. [TBD: verify]. See the Wikipedia Ground state article.
group. See group of entities.
group identity. Common identity for all members of a group.
group of entities. A collection of entities which share a group identity due to some set of common characteristics among the individual members.
group of users. A user generally belongs to a group, such as a project, organization, or team. Access control is commonly based on the group to which a user belongs.
Grover iteration. TBD. See also: Grover’s algorithm.
Grover operator. See Grover iteration.
Grover’s algorithm. A quantum algorithm which finds the input to a particular function which produces a specified output value significantly more efficiently than a comparable algorithm for a classical computer. Commonly considered a solution for searching of a database. See the Wikipedia Grover’s algorithm article. See famous quantum algorithms.
GST. Initialism for gate set tomography or quantum gate set tomography.

To browse other parts of the glossary:

Quantum Computing Glossary — Part 2 — D-G

D-G

Written by Jack Krupansky

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