# Quantum Computing Glossary — Part 2 — D-G

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

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

# 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 thepaper by Benedetti, et al.*A generative modeling approach for benchmarking and training shallow quantum circuits***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 Wikipediaarticle.*Data science***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 Wikipediaarticle.*SQL***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 Wikipediaarticle.*Decimal***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*.**degenerate ground state system.**TBD. Referenced in thepaper by Nagata, Kuramitani, Sekiguchi, and Kosaka.*Universal holonomic quantum gates over geometric spin qubits with polarised microwaves***degenerate V-type qutrit system.**TBD. Referenced in thepaper by Nagata, Kuramitani, Sekiguchi, and Kosaka.*Universal holonomic quantum gates over geometric spin qubits with polarised microwaves***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 Wikipediaarticle. Abbreviated as*Density functional theory**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 Wikipediaarticle.*Quantum logic gate***Deutsch-Jozsa algorithm.**TBD. See the Wikipediaarticle.*Deutsch-Jozsa algorithm***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 inbill. See also:*National Quantum Initiative Act**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 Wikipediaarticle.*Adiabatic process***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 Wikipediaarticle.*Main diagonal***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 thepaper.*A digital quantum simulator in the presence of a bath***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 Wikipediaarticle. Synonym for*Dilution refrigerator**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 thepaper by Brunner, Pironio, Acin, Gisin, Methot, Scarani.*Testing the Hilbert space dimension***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 Wikipediaarticle. See also:*Bra–ket notation**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 Wikipediaarticle.*Direct current***direct embedding.**TBD. A*programming model*for the D-Wave*quantum computer*. See thewhitepaper and the*Programming with D-Wave: Map Coloring Problem*paper by Cao, Jiang, Perouli, and Kais. See also:*Solving Set Cover with Pairs Problem using Quantum Annealing**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 Wikipediaarticle. See also:*Discrete Fourier transform**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 Wikipediaarticle.*Discrete logarithm***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 Wikipediaarticle.*Quantum walk***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 thepaper by DiVincenzo of IBM.*The Physical Implementation of Quantum Computation***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 Wikipediaarticle. See also:*Domain of a function**range of a function*.**dot product.**TBD. See also:*inner product*. See the Wolfram MathWorldpage and the Wikipedia*Dot Product*article.*Dot product***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 Wikipediaarticle. See also:*Double-precision floating-point format**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 thepaper by Nagata, Kuramitani, Sekiguchi, and Kosaka.*Universal holonomic quantum gates over geometric spin qubits with polarised microwaves***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 Wikipediaarticle. See also:*Dynamical system**chaos theory*and*quantum chaos theory*.**e.**Symbolic name for*Euler’s number*. See the Wikipediaarticle.*e (mathematical constant)***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 thepaper by Grzesiak, et al.*Efficient Arbitrary Simultaneously Entangling Gates on a trapped-ion quantum computer***efficient, arbitrary, simultaneously entangling gate.**TBD. Abbreviated as*EASE gate*. Referenced in thepaper by Grzesiak, et al.*Efficient Arbitrary Simultaneously Entangling Gates on a trapped-ion quantum computer***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 Wikipediaarticle.*Eigenvalues and eigenvectors***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 Wikipediaarticle. Also referred to as the*EPR paradox**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 Wikipediaarticle.*Electric current***electric field.**TBD. See the Wikipediaarticle. See also:*Electric field**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*, and*Magnetic field*articles. Synonym for*Electromagnetic field**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 Wikipediaarticle. Shortened as*Power supply**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 Wikipediaarticle.*Electromagnetic field***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 Wikipediaarticle. Quantum computers may make use of EMR, such as*Electromagnetic radiation**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 Wikipediaarticle. See also*Electromagnetism**electric field*and*magnetic field*. Synonym for*electromagnetic radiation*(*EMR*).**electron.**The*elementary particle*associated with holding and transmitting*charge*. See the Wikipediaarticle. See also:*Electron**electronic*,*electronic circuit*,*electrical*.**electron−nucleus entanglement.**TBD. Referenced in thepaper by Nagata, Kuramitani, Sekiguchi, and Kosaka.*Universal holonomic quantum gates over geometric spin qubits with polarised microwaves***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 Wikipediaarticle.*Electronics***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 Wikipediaarticle. See also:*Electronic component**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 Wikipediaarticle.*Elementary particle***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 thepaper by Smith, Curtis, and Zeng of Rigetti Computing. Abbreviated as*A Practical Quantum Instruction Set Architecture**EDSL*. Seefrom Microsoft.*Language-Integrated Quantum Operations: LIQUi|>***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 Wikipediaarticle.*Encryption***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 thepaper. See also*Scalable Quantum Computing With “Enhancement” Quantum Dots**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 Wikipediaarticle.*Quantum entanglement***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 Wikipediaarticle.*ECC memory**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 Wikipediaarticle. Symbolized as*e (mathematical constant)**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 Wikipediaarticle.*Euler’s totient function***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 Wikipediaarticle.*Evolutionary algorithm***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 thepaper.*A quantum-inspired classical algorithm for recommendation systems***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 Wikipediaarticle.*Excited state***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 Wikipediaarticle.*Expectation value (quantum mechanics)***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 Wikipediaarticle.*Time complexity***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 p*roblem*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 thepaper by Jozsa and Van den Nest.*Classical simulation complexity of extended Clifford circuits***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 Wikipediaarticle. See also:*Extended precision**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 wikipediaarticle.*XML***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 thepaper by Shor. See also:*Polynomial-Time Algorithms for Prime Factorization and Discrete Logarithms on a Quantum Computer**finding discrete logarithms*.**factoring integers and finding discrete logarithms.**TBD. Referenced in thepaper by Shor.*Polynomial-Time Algorithms for Prime Factorization and Discrete Logarithms on a Quantum Computer***falsify.**Test and confirm whether a proposition or*theory*is false. See also:*falsify a theory*. See the Wikipediaarticle.*Falsifiability***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 Wikipediaarticle.*Faraday cage***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 Wikipediaarticle.*Faraday cage***fast and fault-tolerant manipulation.**TBD. Referenced in thepaper by Nagata, Kuramitani, Sekiguchi, and Kosaka.*Universal holonomic quantum gates over geometric spin qubits with polarised microwaves***fast Fourier transform.**TBD. See the Wikipediaarticle. Abbreviated as*Fast Fourier transform**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 Wikipediaarticle.*Fault tolerance***fault-tolerant.**See*fault tolerance.***fault tolerant.**See*fault tolerance.***fault-tolerant holonomic quantum computing.**TBD. Referenced in thepaper by Nagata, Kuramitani, Sekiguchi, and Kosaka.*Universal holonomic quantum gates over geometric spin qubits with polarised microwaves***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 thepaper by Nagata, Kuramitani, Sekiguchi, and Kosaka.*Universal holonomic quantum gates over geometric spin qubits with polarised microwaves***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 Wikipediaarticle.*Fermi–Dirac statistics***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 Wikipediaarticle.*Fermion***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 Wikipediaarticle.*Figure of merit***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 thepaper by Shor. See also:*Polynomial-Time Algorithms for Prime Factorization and Discrete Logarithms on a Quantum Computer**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 Wikipediaarticle. Shortened as*Finite-state machine**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:by Bernard Zygelman. There’s only one catch — it’s not due until*A First Introduction to Quantum Computing and Information**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 Wikipediaarticle. And this short article from IBM,*Quantum computing*. And this reasonably decent tutorial from Emma Strubell,*Introduction to Quantum Computing*, and*Introduction to Quantum Computing — Part I*. And for those a bit more ambitious,*Part II*from Peter Shor’s lecture notes on*Lecture 19: How to Build Your Own Quantum Computer*.*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 byas of July 2018.*IBM Q***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 Wikipediaarticle. See also:*Flash memory**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 indoc from Rigetti Computing.*The Quantum Processing Unit (QPU)***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 Wikipediaarticle. Other types of*Flux qubit**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 thepaper by Nagata, Kuramitani, Sekiguchi, and Kosaka. See the*Universal holonomic quantum gates over geometric spin qubits with polarised microwaves*article.*Flying qubits make for a highly resilient quantum memory***Fock state.**TBD. See thepaper by Didier, Sete, da Silva, Rigetti. See also:*Analytical modeling of parametrically-modulated transmon qubits**parametrically-activated entangling gates*.**force.**The ability to*cause*an*effect*. See the Wikipediaarticle.*Force***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 “” paper by Aaronson and Ambainis.*Forrelation: A Problem that Optimally Separates Quantum from Classical Computing***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 thepaper by Beauregard.*Circuit for Shor’s algorithm using 2n+3 qubits***Fourier transform.**TBD. See the Wikipediaarticle. See also:*Fourier transform**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 Wikipediaarticle.*Quantum logic gate***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 Wikipediaarticle.*Frequency***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 thepaper from Hutchings, Hertzberg, Liu, Bronn, Keefe, Chow, and Plourde. Shortened as*Tunable Superconducting Qubits with Flux-Independent Coherence**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 thepaper by Foxen, et al.*Demonstrating a Continuous Set of Two-qubit Gates for Near-term Quantum Algorithms***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 thepaper.*16-qubit IBM universal quantum computer can be fully entangled***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 thepaper by Nagata, Kuramitani, Sekiguchi, and Kosaka.*Universal holonomic quantum gates over geometric spin qubits with polarised microwaves***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 reasonable 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 Wikipediaarticle. Abbreviated as*Genetic algorithm**GA*.**genetic programming.**See*genetic algorithm (GA)*and*evolutionary algorithm (EA)*. Abbreviated as*GP*. See the Wikipediaarticle.*Genetic programming***geometric entangled states.**TBD. Referenced in thepaper by Nagata, Kuramitani, Sekiguchi, and Kosaka.*Universal holonomic quantum gates over geometric spin qubits with polarised microwaves***geometric measure of coherence.**TBD.**geometric phase gate.**TBD. Referenced in thepaper by Nagata, Kuramitani, Sekiguchi, and Kosaka.*Universal holonomic quantum gates over geometric spin qubits with polarised microwaves***geometric phase space.**TBD. Referenced in thepaper by Nagata, Kuramitani, Sekiguchi, and Kosaka.*Universal holonomic quantum gates over geometric spin qubits with polarised microwaves***geometric spin qubit.**TBD. Referenced in thepaper by Nagata, Kuramitani, Sekiguchi, and Kosaka.*Universal holonomic quantum gates over geometric spin qubits with polarised microwaves***geometric spin state measurement.**TBD. Referenced in thepaper by Nagata, Kuramitani, Sekiguchi, and Kosaka.*Universal holonomic quantum gates over geometric spin qubits with polarised microwaves***geometric spin state preparation.**TBD. Referenced in thepaper by Nagata, Kuramitani, Sekiguchi, and Kosaka.*Universal holonomic quantum gates over geometric spin qubits with polarised microwaves***geometric spin state preparation and measurement.**TBD. Referenced in thepaper by Nagata, Kuramitani, Sekiguchi, and Kosaka.*Universal holonomic quantum gates over geometric spin qubits with polarised microwaves***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 Wikipediaarticle.*Backus–Naur form***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 Wikipediaarticle. See also:*Graph theory**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 Wikipediaarticle. See also:*Greenberger–Horne–Zeilinger state**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 Wikipediaarticle.*Ground state***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 Wikipediaarticle. See*Grover’s algorithm**famous quantum algorithms*.**GST.**Initialism for*gate set tomography*or*quantum gate set tomography*.

To browse other parts of the glossary:

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