View source for Glossary of quantum computing

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This '''glossary of quantum computing''' is a list of definitions of terms and concepts used in [[quantum computing]], its sub-disciplines, and related fields.
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{{glossary}}

{{term|[[Bacon–Shor code]]}}
{{defn|is a Subsystem [[Quantum error correction|error correcting code]].<ref>{{Cite journal|last=Bacon|first=Dave|date=2006-01-30|title=Operator quantum error-correcting subsystems for self-correcting quantum memories|journal=Physical Review A|volume=73|issue=1|pages=012340|doi=10.1103/PhysRevA.73.012340|arxiv=quant-ph/0506023|bibcode=2006PhRvA..73a2340B|s2cid=118968017}}</ref> In a Subsystem code, information is encoded in a [[System#Subsystem|subsystem]] of a [[Hilbert space]]. Subsystem codes lend to simplified error correcting procedures unlike codes which encode information in the [[Space (mathematics)|subspace]] of a Hilbert space.<ref>
{{Cite book
 |author = Aly Salah A., Klappenecker, Andreas
 |title = 2008 IEEE International Symposium on Information Theory
 |chapter = Subsystem code constructions
 |arxiv = 0712.4321
 |year = 2008
 |pages = 369–373
|doi = 10.1109/ISIT.2008.4595010
 |isbn = 978-1-4244-2256-2
 |s2cid = 14063318
 }}</ref>  This simplicity led to the first demonstration of fault tolerant circuits on a quantum computer.<ref>
{{Cite journal
 |title = Fault-tolerant control of an error-corrected qubit. 
 |author = Egan, L., Debroy, D.M., Noel, C.
 |journal = Phys. Rev. Lett.
 |arxiv=2009.11482
 |issue = 7880
 |pages = 281–286
 |year = 2021
 |volume = 598
 |publisher = Nature
 |doi = 10.1038/s41586-021-03928-y

|pmid = 34608286
 |bibcode = 2021Natur.598..281E
 |s2cid = 238357892
 }}</ref> }}

{{term|[[BQP]]}}
{{defn|In [[computational complexity theory]], bounded-error quantum polynomial time (BQP) is the class of [[decision problems]] solvable by a [[quantum computer]] in [[polynomial time]], with an error probability of at most 1/3 for all instances.<ref name="Chuang2000">Michael Nielsen and Isaac Chuang (2000). ''Quantum Computation and Quantum Information''. Cambridge: Cambridge University Press. {{isbn|0-521-63503-9}}.</ref> It is the quantum analogue to the [[complexity class]] '''[[BPP (complexity)|BPP]]'''.  A decision problem is a member of  BQP if there exists a [[quantum algorithm]] (an [[algorithm]] that runs on a quantum computer) that solves the decision problem [[with high probability]] and is guaranteed to run in polynomial time. A run of the algorithm will correctly solve the decision problem with  a probability of at least 2/3.}}

{{term|[[Classical shadow]]}}
{{defn|is a protocol for predicting functions of a [[quantum state]] using only a [[logarithm]]ic number of [[Quantum measurement|measurements]].<ref name="Huang2020">{{Cite journal | arxiv=2002.08953|last1=Huang |first1=Hsin-Yuan |last2=Kueng |first2=Richard |last3=Preskill|first3=John |title =Predicting many properties of a quantum system from very few measurements|year=2020 |journal=Nat. Phys.|volume=16 | issue=10 |pages=1050–1057|doi=10.1038/s41567-020-0932-7|bibcode=2020NatPh..16.1050H |s2cid=211205098 }}</ref> Given an unknown state <math> \rho </math>, a [[Quantum tomography|tomographically complete]] set of [[Quantum logic gate|gates]] <math> U</math> (e.g [[Clifford gates]]), a set of <math>M</math> [[observable]]s <math>\{O_{i}\}</math> and a [[quantum channel]] <math>M</math> (defined by randomly sampling from <math>U</math>, applying it to <math>\rho</math> and measuring the resulting state); predict the [[Expectation value (quantum mechanics)|expectation values]] <math>\operatorname{tr}(O_{i} \rho)</math>.<ref name="Koh2020">{{cite journal | arxiv=2011.11580|last1= Koh |first1=D. E. |last2=Grewal|first2= Sabee |title=Classical Shadows with Noise|journal= Quantum |year=2022|volume= 6 |page= 776 |doi= 10.22331/q-2022-08-16-776 |bibcode= 2022Quant...6..776K |s2cid= 227127118 }}</ref> A list of classical shadows <math>S</math> is created using <math>\rho</math>, <math>U</math> and <math>M</math> by running a Shadow generation algorithm. When predicting the properties of <math>\rho</math>, a Median-of-means estimation algorithm is used to deal with the outliers in <math>S</math>.<ref>{{Cite journal | arxiv=2008.05234|last1=Struchalin |first1=G.I. |last2=Zagorovskii |first2=Ya. A. |last3=Kovlakov |first3=E.V. |last4=Straupe | first4=S.S. |last5=Kulik |first5= S.P.|title=Experimental Estimation of Quantum State Properties from Classical Shadows|year=2021 |journal=PRX Quantum|volume=2 | issue=1 |page=010307 |doi=10.1103/PRXQuantum.2.010307|s2cid=221103573 }}</ref> Classical shadow is useful for [[Fidelity of quantum states|direct fidelity estimation]], entanglement verification, estimating [[Correlation function (statistical mechanics)|correlation functions]], and predicting [[Entropy of entanglement|entanglement entropy]].<ref name=Huang2020/>}}

{{term|[[Cloud-based quantum computing]]}}
{{defn|is the invocation of quantum [[emulators]], [[simulators]] or processors through the cloud. Increasingly, cloud services are being looked on as the method for providing access to quantum processing. Quantum computers achieve their massive computing power by initiating [[Quantum mechanics|quantum physics]] into processing power and when users are allowed access to these quantum-powered computers through the internet it is known as [[quantum computing]] within the cloud.}}

{{term|[[Cross-entropy benchmarking]]}}
{{defn|(also referred to as XEB), is [[quantum computer|quantum]] benchmarking protocol which can be used to demonstrate [[quantum supremacy]].<ref>{{Cite journal
 |last1=Boixo |first1=S.
 |display-authors=etal
 |year = 2018
 |title = Characterizing Quantum Supremacy in Near-Term Devices
 |journal = Nature Physics
 |volume = 14
 |issue = 6
 |pages = 595–600
 |arxiv=1608.00263
 |bibcode = 2018NatPh..14..595B
 |doi = 10.1038/s41567-018-0124-x
 |s2cid = 4167494
 }}</ref> In XEB, a random [[quantum circuit]] is executed on a quantum computer multiple times in order to collect a set of <math> k </math> samples in the form of [[bitstring]]s <math>\{x_{1}, \dots, x_{k}\}</math>. The bitstrings are then used to calculate the cross-entropy benchmark fidelity (<math>F_{\rm XEB}</math>) via a [[Computer#Digital computers|classical computer]], given by 
:<math>F_{\rm XEB}= 2^{n} \langle P(x_{i}) \rangle_{k} - 1 =  \frac{2^{n}}{k} \left(\sum_{i=1}^{k}|\langle 0^{n}|C|x_{i}\rangle|^{2}\right) - 1</math>,
where <math>n</math> is the number of [[qubit]]s in the circuit and <math>P(x_{i}) </math> is the probability of a bitstring <math>{x_{i}}</math> for an ideal quantum circuit <math>C</math>.  If <math>F_{XEB} = 1</math>, the samples were collected from a noiseless quantum computer. If <math>F_{\rm XEB} = 0</math>, then the samples could have been obtained via random guessing.<ref>
 {{Cite arXiv
 |last1=Aaronson |first1=S.
 |title = Open Problems Related to Quantum Query Complexity
 |eprint=2109.06917
 |year = 2021
 |class=quant-ph
 }}</ref> This means that if a quantum computer did generate those samples, then the quantum computer is too noisy and thus has no chance of performing beyond-classical computations. Since it takes an exponential amount of resources to classically simulate a quantum circuit, there comes a point when the biggest supercomputer that runs the best classical algorithm for simulating quantum circuits can't compute the XEB. Crossing this point is known as achieving quantum supremacy; and after entering the quantum supremacy regime, XEB can only be estimated.<ref name="Arute19">
{{Cite journal
 |last1=Arute |first1=F.
 |display-authors=etal
 |year = 2019
 |title = Quantum supremacy using a programmable superconducting processor
 |journal = Nature 
 |volume = 574
 |issue = 7779
 |pages = 505–510
 |arxiv = 1910.11333
 |bibcode = 2019Natur.574..505A
 |doi = 10.1038/s41586-019-1666-5
 |pmid = 31645734
 |s2cid = 204836822

 }}</ref>}}

{{term|[[Eastin–Knill theorem]]}}

{{defn|is a [[no-go theorem]] that states: "No [[quantum error correcting code]] can have a [[continuous symmetry]] which acts transversely on physical qubits".<ref name="EN09">{{Cite journal | arxiv = 0811.4262 |last1= Eastin | first1= Bryan |last2= Knill|first2= Emanuel |title = Restrictions on Transversal Encoded Quantum Gate Sets|journal = Physical Review Letters|volume = 102|issue = 11|pages = 110502|year = 2009|doi = 10.1103/PhysRevLett.102.110502|pmid = 19392181|bibcode = 2009PhRvL.102k0502E|s2cid= 44457708 }}</ref> In other words, no quantum error correcting code can transversely implement a [[Quantum logic gate#Universal quantum gates|universal gate set]]. Since quantum computers are inherently noisy, quantum error correcting codes are used to correct errors that affect information due to [[decoherence]].  Decoding error corrected data in order to perform gates on the qubits makes it prone to errors.  Fault tolerant quantum computation avoids this by performing gates on encoded data. Transversal gates, which perform a gate between two "logical" qubits each of which is encoded in ''N'' "physical qubits" by pairing up the physical qubits of each encoded qubit ("code block"), and performing independent gates on each pair, can be used to perform fault tolerant but not universal quantum computation because they guarantee that errors don't spread uncontrollably through the computation.  This is because transversal gates ensure that each qubit in a code block is acted on by at most a single physical gate and each code block is corrected independently when an error occurs. Due to the Eastin–Knill theorem, a universal set like {{math|{''[[Quantum logic gate#Hadamard gate|H]], [[Quantum logic gate#Phase shift|S]]'', [[CNOT]], ''[[Quantum logic gate#Phase shift|T]]'' }}} gates can't be implemented transversally. For example, the ''T'' gate can't be implemented transversely in the [[Steane code]].<ref>{{Cite journal | arxiv = quant-ph/0403025 |last1=Campbell |first1=Earl T. |last2=Terhal | first2=Barbara M. |last3=Vuillot |first3= Christophe  |title = Roads towards fault-tolerant universal quantum computation|year = 2016 |journal=[[Nature (journal)|Nature]] |volume=549 |issue=7671 |pages=172–179 |doi=10.1038/nature23460|pmid=28905902 |bibcode=2017Natur.549..172C |s2cid=4446310 }}</ref> This calls for ways of [[#Circumventing the theorem|circumventing]] Eastin–Knill in order to perform fault tolerant quantum computation. In addition to investigating fault tolerant quantum computation, the Eastin–Knill theorem is also useful for studying [[quantum gravity]] via the [[AdS/CFT correspondence]] and in [[condensed matter physics]] via [[quantum reference frame]]<ref name="woods19">{{Cite journal | arxiv = 1902.07725 |last1= Woods|first1=Mischa |last2= Alhambra | first2= Alvaro M.|title = Continuous groups of transversal gates for quantum error correcting codes from finite clock reference frames|year = 2020 |journal=Quantum |volume=4 |pages=245 |doi=	10.22331/q-2020-03-23-245|bibcode= 2020Quant...4..245W|s2cid= 119302752}}</ref> or [[many-body theory]].<ref name="Faist19">{{Cite journal | arxiv = 1902.07714 |last1 = Faist |first1 = Philippe |last2 = Nezami | first2 = Sepehr | last3 =  V. Albert | first3 = Victor |last4 = Salton | first4= Grant |last5 =  Pastawski | first5=  Fernando |last6 = Hayden | first6= Patrick |last7 = Preskill | first7= John |title = Continuous Symmetries and Approximate Quantum Error Correction|journal = Physical Review X |year =  2020|volume = 10 |issue = 4 |page = 041018 |doi = 10.1103/PhysRevX.10.041018 |bibcode = 2020PhRvX..10d1018F |s2cid = 119207861 }}</ref>}}

{{term|[[Five-qubit error correcting code]]}}
{{defn|is the smallest [[quantum error correction|quantum error correcting]] code that can protect a [[Physical and logical qubits|logical qubit]] from any arbitrary single qubit error.<ref>{{cite arXiv | eprint=0904.2557|last1=Gottesman |first1=Daniel|title =An Introduction to Quantum Error Correction and Fault-Tolerant Quantum Computation|year=2009|class=quant-ph }}</ref> In this code, 5 [[Physical and logical qubits|physical qubits]] are used to encode the logical qubit.<ref>
{{Cite journal
 |title = Benchmarking Quantum Computers: The Five-Qubit Error Correcting Code
 |author = Knill, E. and Laflamme, R. and Martinez, R. and Negrevergne, C.
 |journal = Phys. Rev. Lett.
 |arxiv=quant-ph/0101034
 |volume = 86
 |issue = 25
 |pages = 5811–5814
 |year = 2001
 |publisher = American Physical Society
 |doi = 10.1103/PhysRevLett.86.5811
 |pmid = 11415364
 |bibcode = 2001PhRvL..86.5811K
 |s2cid = 119440555
 |url = https://link.aps.org/doi/10.1103/PhysRevLett.86.5811

}}</ref> With <math>X</math> and <math>Z</math> being [[Pauli matrices]] and <math>I</math> the [[Identity matrix]], this code's [[Stabilizer code#Definition|generators]] are <math> \langle XZZXI, IXZZX, XIXZZ,ZXIXZ \rangle</math>. Its logical operators are <math>\bar{X} = XXXXX </math> and  <math>\bar{Z} = ZZZZZ</math>.<ref>{{cite arXiv
|title=Stabilizer Codes and Quantum Error Correction
|author=D. Gottesman

|arxiv=quant-ph/9705052
|year=1997
}}</ref>  Once the logical qubit is encoded, errors on the physical qubits can be detected via stabilizer measurements. A [[lookup table]] that maps the results of the stabilizer measurements to the types and locations of the errors gives the control system of the quantum computer enough information to correct errors.<ref name="introductory2019">
{{Cite journal
|author = Roffe Joschka
|title = Quantum error correction: an introductory guide
|arxiv=1907.11157
|journal = Contemporary Physics
|volume = 60
|number = 3
|pages = 226–245
|year= 2019
|publisher=Taylor & Francis
|doi = 10.1080/00107514.2019.1667078
|bibcode = 2019ConPh..60..226R
|s2cid = 198893630
|url=https://doi.org/10.1080/00107514.2019.1667078

}}</ref>}}

{{term|[[Hadamard test (quantum computation)]]}}

{{defn| is a method used to create a [[random variable]] whose [[expected value]] is the expected [[real part]] <math>\mathrm{Re}\langle\psi| U|\psi\rangle</math>, where <math> |\psi\rangle </math> is a quantum state and <math>U</math> is a [[quantum gate|unitary gate]] acting on the space of <math>|\psi\rangle</math>.<ref name="DA2009">
{{cite journal
  | author = [[Dorit Aharonov]] [[Vaughan Jones]], Zeph Landau
  | title = A Polynomial Quantum Algorithm for Approximating the Jones Polynomial
  | journal = Algorithmica 
  | volume = 55
  | issue = 3
  | pages = 395–421
  | year = 2009
  | doi = 10.1007/s00453-008-9168-0
  | arxiv = quant-ph/0511096
  | s2cid = 7058660
 }}

</ref> The Hadamard test produces a random variable whose [[Image (mathematics)|image]] is in <math>\{\pm 1\}</math> and whose expected value is exactly <math>\mathrm{Re}\langle\psi| U|\psi\rangle</math>. It is possible to modify the circuit to produce a random variable whose expected value is <math>\mathrm{Im}\langle\psi| U|\psi\rangle</math>.<ref name="DA2009" />}}

{{term|[[Magic state distillation]]}}

{{defn|is a process that takes in multiple noisy [[quantum state]]s and outputs a smaller number of more reliable quantum states. It is considered by many experts<ref>{{cite journal |last1=Campbell |first1=Earl T. |last2=Terhal |first2=Barbara M. |last3=Vuillot |first3=Christophe |title=Roads towards fault-tolerant universal quantum computation |journal=Nature |date=14 September 2017 |volume=549 |issue=7671 |pages=172–179 |doi=10.1038/nature23460|pmid=28905902 |arxiv=1612.07330 |bibcode=2017Natur.549..172C |s2cid=4446310 |url=http://eprints.whiterose.ac.uk/121343/1/1612.07330.pdf }}</ref> to be one of the leading proposals for achieving [[fault tolerant]] [[quantum computation]]. Magic state distillation has also been used to argue <ref>{{cite journal |last1=Howard |first1=Mark |last2=Wallman |first2=Joel |last3=Veitch |first3=Victor |last4=Emerson |first4=Joseph |title=Contextuality supplies the 'magic' for quantum computation |journal=Nature |date=11 June 2014 |volume=510 |issue=7505 |pages=351–355 |doi=10.1038/nature13460|pmid=24919152 |arxiv=1401.4174 |bibcode=2014Natur.510..351H |s2cid=4463585 }}</ref>  that [[quantum contextuality]] may be the "magic ingredient" responsible for the power of quantum computers.<ref>{{cite journal |last1=Bartlett |first1=Stephen D. |title=Powered by magic |journal=Nature |date=11 June 2014 |volume=510 |issue=7505 |pages=345–347 |doi=10.1038/nature13504|pmid=24919151 |doi-access=free }}</ref>  }}

{{term|[[Mølmer–Sørensen gate]]}}

{{defn|(or MS gate), is a two [[qubit]] [[Quantum gate|gate]] used in [[Trapped ion quantum computer|trapped ion]] [[quantum computing]]. It was proposed by [[Klaus Mølmer]] and Anders Sørensen.<ref>Sørensen, Anders; Mølmer, Klaus (March 1, 1999). "Multi-particle entanglement of hot trapped ions". Physical Review Letters. 82 (9): 1835–1838. arXiv:quant-ph/9810040. Bibcode:1999PhRvL..82.1835M. doi:10.1103/PhysRevLett.82.1835. S2CID 49333990.</ref>  Their proposal also extends to gates on more than two qubits.}}

{{term|[[Quantum algorithm]]}}
{{defn|is an [[algorithm]] which runs on a realistic model of [[quantum computation]], the most commonly used model being the [[quantum circuit]] model of computation.<ref>{{cite book|title=Quantum Computation and Quantum Information|last1=Nielsen|first1=Michael A.|last2=Chuang|first2=Isaac L.|publisher=[[Cambridge University Press]]|year=2000|isbn=978-0-521-63503-5|author-link=Michael Nielsen|author-link2=Isaac Chuang|title-link=Quantum Computation and Quantum Information}}</ref><ref>{{cite arXiv|eprint=0808.0369|class=quant-ph|first=M.|last=Mosca|author-link=Michele Mosca|title=Quantum Algorithms|date=2008}}</ref> A classical (or non-quantum) algorithm is a finite sequence of instructions, or a step-by-step procedure for solving a problem, where each step or instruction can be performed on a classical [[computer]]. Similarly, a quantum algorithm is a step-by-step procedure, where each of the steps can be performed on a [[quantum computer]]. Although all classical algorithms can also be performed on a quantum computer,<ref>{{Cite book|title = Quantum Computer Science|url = https://books.google.com/books?id=-wkJIuw0YRsC&q=quantum%2520computer%2520equivalent%2520classical%2520computer&pg=PA23|publisher = Morgan & Claypool Publishers|date = 2009-01-01|isbn = 9781598297324|first1 = Marco|last1 = Lanzagorta|first2 = Jeffrey K.|last2 = Uhlmann}}</ref>{{rp|126}}  the term quantum algorithm is usually used for those algorithms which seem inherently quantum, or use some essential feature of quantum computation such as [[quantum superposition]] or [[quantum entanglement]].}}

{{term|[[Quantum computing]]}}
{{defn|is a type of [[computation]] whose operations can harness the phenomena of [[quantum mechanics]], such as [[quantum superposition|superposition]], [[Wave interference#Quantum interference|interference]], and [[quantum entanglement|entanglement]]. Devices that perform quantum computations are known as quantum computers.<ref name="Hidary">{{cite book | last=Hidary | first=Jack | title=Quantum computing : an applied approach | publisher=Springer | publication-place=Cham | date=2019 | isbn=978-3-030-23922-0 | oclc=1117464128 | page=3}}</ref>{{sfn|Nielsen|Chuang|2010|p=1}} Though current quantum computers are too small to outperform usual (classical) computers for practical applications, larger realizations are believed to be capable of solving certain [[computational problem]]s, such as [[integer factorization]] (which underlies [[RSA encryption]]), substantially faster than classical computers. The study of quantum computing is a subfield of [[quantum information science]].
}}

{{term|[[Quantum volume]]}}
{{defn|is a metric that measures the capabilities and error rates of a [[Quantum computing|quantum computer]]. It expresses the maximum size of square [[quantum circuit]]s that can be implemented successfully by the computer. The form of the circuits is independent from the quantum computer architecture, but compiler can transform and optimize it to take advantage of the computer's features. Thus, quantum volumes for different architectures can be compared.}}

{{term|[[Quantum error correction]]}}
{{defn|(QEC), is used in [[Quantum computer|quantum computing]] to protect [[quantum information]] from errors due to [[decoherence]] and other [[quantum noise]]. Quantum error correction is theorised as essential to achieve [[fault-tolerant quantum computation]] that can reduce the effects of noise on stored quantum information, faulty quantum gates, faulty quantum preparation, and faulty measurements.}}

{{term|[[Quantum image processing]]}}
{{defn|(QIMP), is using [[quantum computing]] or [[quantum information processing]] to create and work with [[quantum image]]s.<ref name="Venegas-Andraca2005">{{cite thesis |last= Venegas-Andraca |first= Salvador E.|date= 2005 |title= Discrete Quantum Walks and Quantum Image Processing|type= DPhil thesis|publisher= The University of Oxford|url= https://ora.ox.ac.uk/objects/uuid:2baab08b-ee68-4ce5-8e68-8201f086a1ba}}</ref><ref name="Iliyasu Towards 2013">{{cite journal |title=Towards realising secure and efficient image and video processing applications on quantum computers |journal=Entropy |volume=15 |issue=8 |pages=2874–2974 |year=2013 |last1=Iliyasu |first1=A.M.|bibcode=2013Entrp..15.2874I |doi=10.3390/e15082874 |doi-access=free }}</ref>

Due to some of the properties inherent to quantum computation, notably [[Quantum entanglement|entanglement]] and [[Parallel computing|parallelism]], it is hoped that QIMP technologies will offer capabilities and performances that surpass their traditional equivalents, in terms of computing speed, security, and minimum storage requirements.<ref name="Iliyasu Towards 2013" /><ref name="Yan Quantum 2017">{{cite journal |title=Quantum image processing: A review of advances in its security technologies |journal=International Journal of Quantum Information |volume=15 |issue=3 |pages=1730001–44 |year=2017 |last1=Yan |first1=F.|last2=Iliyasu |first2=A.M.|last3=Le |first3=P.Q.|doi=10.1142/S0219749917300017 |bibcode=2017IJQI...1530001Y |doi-access=free }}</ref>}}

{{term|[[Quantum programming]]}}
{{defn|is the process of [[Assembly language|assembling]] sequences of instructions, called quantum programs, that are capable of running on a [[Quantum computing|quantum computer]]. Quantum [[programming language]]s help express [[quantum algorithm]]s using high-level constructs.<ref>{{Cite book| author=Jarosław Adam Miszczak |title= High-level Structures in Quantum Computing | isbn=9781608458516|year= 2012 |publisher= Morgan & Claypool Publishers }}</ref> The field is deeply rooted in the [[Open source|open-source]] philosophy and as a result most of the quantum software discussed in this article is freely available as [[Open source software|open-source software]].<ref>{{Cite web|url=https://github.com/qosf/awesome-quantum-software|title=Comprehensive list of quantum open-source projects|website=Github|access-date=2022-01-27}}</ref>}}

{{term|[[Quantum simulator]]}}
{{defn| Quantum simulators permit the study of [[quantum system]] in a programmable fashion. In this instance, simulators are special purpose devices designed to provide insight about specific [[physics]] problems.<ref name=Johnson2014>{{cite journal
|doi=10.1140/epjqt10
|title=What is a quantum simulator?
|year=2014
|last1=Johnson
|first1=Tomi H.
|last2=Clark
|first2=Stephen R.
|last3=Jaksch
|first3=Dieter
|journal=EPJ Quantum Technology
|volume=1
|number=10|page=10
|arxiv=1405.2831
|bibcode=2014EPJQT...1...10J
|s2cid=120250321
}}</ref><ref name=nist-pg>
{{NIST-PD
|article=NIST Physicists Benchmark Quantum Simulator with Hundreds of Qubits
|Date= May 2, 2012
|url=https://www.nist.gov/public_affairs/tech-beat/tb20120502.cfm/
|author=Michael E. Newman
|accessdate=2013-02-22}}</ref><ref name=Britton>
{{cite journal
|doi=10.1038/nature10981
|url=http://tf.boulder.nist.gov/general/pdf/2614.pdf
|arxiv=1204.5789 
|bibcode = 2012Natur.484..489B
|title=Engineered two-dimensional Ising interactions in a trapped-ion quantum simulator with hundreds of spins
|year=2012
|last1=Britton
|first1=Joseph W.
|last2=Sawyer
|first2=Brian C.
|last3=Keith
|first3=Adam C.
|last4=Wang
|first4=C.-C. Joseph
|last5=Freericks
|first5=James K.
|last6=Uys
|first6=Hermann
|last7=Biercuk
|first7=Michael J.
|last8=Bollinger
|first8=John J.
|journal=Nature
|volume=484
|issue=7395
|pages=489–92
|pmid=22538611 |s2cid=4370334
}} 
Note: This manuscript is a contribution of the US National Institute of Standards and Technology and is not subject to US copyright.</ref> Quantum simulators may be contrasted with generally programmable "digital" [[quantum computing|quantum computers]], which would be capable of solving a wider class of quantum problems.}}

{{term|[[Quantum state discrimination]]}}
{{defn|In [[quantum information science]], '''quantum state discrimination''' refers to the task of inferring the quantum state that produced the observed measurement probabilities.

More precisely, in its standard formulation, the problem involves performing some [[POVM]] <math>(E_i)_i</math> on a given unknown state <math>\rho</math>, under the promise that the state received is an element of a collection of states <math>\{\sigma_i\}_i</math>, with <math>\sigma_i</math> occurring with probability <math>p_i</math>, that is, <math>\rho=\sum_i p_i \sigma_i</math>. The task is then to find the probability of the POVM <math>(E_i)_i</math> correctly guessing which state was received. Since the probability of the POVM returning the <math>i</math>-th outcome when the given state was <math>\sigma_j</math> has the form <math>\text{Prob}(i|j) = \operatorname{tr}(E_i \sigma_j) </math>, it follows that the probability of successfully determining the correct state is <math> P_{\rm success} = \sum_{i} p_{i}\operatorname{tr}(\sigma_{i} E_{i}) </math>.<ref>{{Cite journal | arxiv=1707.02571|last1=Bae |first1=Joonwoo  |last2=Kwek |first2=Leong-Chuan |title =Quantum state discrimination and its applications|year =2015 |journal= Journal of Physics A: Mathematical and Theoretical
|volume=48 |issue=8 |page=083001 |doi=10.1088/1751-8113/48/8/083001|bibcode=2015JPhA...48h3001B |s2cid=119199057 }}</ref>

}}

 
{{term|[[Quantum supremacy]]}}
{{defn|or '''quantum advantage''', is the goal of demonstrating that a programmable quantum device can solve a problem that no classical computer can solve in any feasible amount of time (irrespective of the usefulness of the problem).<ref>{{cite arXiv |last=Preskill |first=John |date=2012-03-26 |title=Quantum computing and the entanglement frontier |eprint=1203.5813 |class=quant-ph}}</ref><ref>{{Cite journal|last=Preskill|first=John|date=2018-08-06|title=Quantum Computing in the NISQ era and beyond|journal=Quantum|volume=2|pages=79|doi=10.22331/q-2018-08-06-79|arxiv=1801.00862 |bibcode=2018Quant...2...79P |doi-access=free}}</ref><ref>Zhong, Han-Sen; Wang, Hui; Deng, Yu-Hao; Chen, Ming-Cheng; Peng, Li-Chao; Luo, Yi-Han; Qin, Jian; Wu, Dian; Ding, Xing; Hu, Yi; Hu, Peng (2020-12-03). "Quantum computational advantage using photons". Science. 370 (6523): 1460–1463. arXiv:2012.01625. Bibcode:2020Sci...370.1460Z. doi:10.1126/science.abe8770. ISSN 0036-8075. PMID 33273064. S2CID 227254333.</ref> Conceptually, quantum supremacy involves both the engineering task of building a powerful quantum computer and the [[computational complexity theory|computational-complexity-theoretic]] task of finding a problem that can be solved by that quantum computer and has a [[Time complexity|superpolynomial]] speedup over the best known or possible classical algorithm for that task.<ref name=":13">{{Cite journal|last1=Harrow|first1=Aram W.|last2=Montanaro|first2=Ashley|date=September 2017|title=Quantum computational supremacy|journal=Nature|volume=549|issue=7671|pages=203–209|doi=10.1038/nature23458|pmid=28905912|issn=1476-4687|arxiv=1809.07442|bibcode=2017Natur.549..203H|s2cid=2514901}}</ref><ref>{{Cite journal |last1=Papageorgiou |first1=Anargyros |last2=Traub |first2=Joseph F. |date=2013-08-12 |title=Measures of quantum computing speedup |journal=Physical Review A |volume=88 |issue=2 |pages=022316 |doi=10.1103/PhysRevA.88.022316 |issn=1050-2947 |arxiv=1307.7488|bibcode=2013PhRvA..88b2316P|s2cid=41867048 }}</ref> The term was coined by [[John Preskill]] in 2012,<ref name=":0" /><ref>"John Preskill Explains 'Quantum Supremacy'". Quanta Magazine. 2 October 2019. Retrieved 2020-04-21.</ref> but the concept of a quantum computational advantage, specifically for simulating quantum systems, dates back to [[Yuri Manin]]'s (1980)<ref name="manin1980vychislimoe">{{cite book
  | author=Manin, Yu. I.
  | title=Vychislimoe i nevychislimoe
  | trans-title=Computable and Noncomputable
  | year=1980
  | publisher=Sov.Radio
  | url=http://publ.lib.ru/ARCHIVES/M/MANIN_Yuriy_Ivanovich/Manin_Yu.I._Vychislimoe_i_nevychislimoe.(1980).%5Bdjv%5D.zip
  | pages=13–15
  | language=ru
  | access-date=2013-03-04
  | url-status=dead
  | archive-url=https://web.archive.org/web/20130510173823/http://publ.lib.ru/ARCHIVES/M/MANIN_Yuriy_Ivanovich/Manin_Yu.I._Vychislimoe_i_nevychislimoe.(1980).%5Bdjv%5D.zip
  | archive-date=2013-05-10
  }}
</ref> and [[Richard Feynman]]'s (1981) proposals of quantum computing.<ref>{{Cite journal |last=Feynman |first=Richard P. |date=1982-06-01 |title=Simulating Physics with Computers |journal=International Journal of Theoretical Physics |volume=21 |pages=467–488 |issue=6–7 |doi=10.1007/BF02650179 |issn=0020-7748 |bibcode=1982IJTP...21..467F|citeseerx=10.1.1.45.9310 |s2cid=124545445 }}</ref> Examples of proposals to demonstrate quantum supremacy include the [[boson sampling]] proposal of [[Scott Aaronson|Aaronson]] and Arkhipov,<ref name=":3">{{Cite book |last1=Aaronson |first1=Scott |last2=Arkhipov |first2=Alex |title=Proceedings of the forty-third annual ACM symposium on Theory of computing |chapter=The computational complexity of linear optics |date=2011 |series=STOC '11 |location=New York, NY, USA |publisher=ACM |pages=333–342 |doi=10.1145/1993636.1993682 |isbn=9781450306911 |arxiv=1011.3245|s2cid=681637 }}</ref> [[D-Wave Systems|D-Wave's]] specialized frustrated cluster loop problems,<ref>{{cite arXiv |last1=King |first1=James |last2=Yarkoni |first2=Sheir |last3=Raymond |first3=Jack |last4=Ozfidan |first4=Isil |last5=King |first5=Andrew D. |last6=Nevisi |first6=Mayssam Mohammadi |last7=Hilton |first7=Jeremy P. |last8=McGeoch |first8=Catherine C. |date=2017-01-17 |title=Quantum Annealing amid Local Ruggedness and Global Frustration |eprint=1701.04579 |class=quant-ph}}</ref> and sampling the output of random [[quantum circuit]]s.<ref name=":1">{{cite arXiv |last1=Aaronson |first1=Scott |last2=Chen |first2=Lijie |date=2016-12-18 |title=Complexity-Theoretic Foundations of Quantum Supremacy Experiments |eprint=1612.05903 |class=quant-ph}}</ref><ref name=":15">{{Cite journal|last1=Bouland|first1=Adam|last2=Fefferman|first2=Bill|last3=Nirkhe|first3=Chinmay|last4=Vazirani|first4=Umesh|date=2018-10-29|title=On the complexity and verification of quantum random circuit sampling|url=http://dx.doi.org/10.1038/s41567-018-0318-2|journal=Nature Physics|volume=15|issue=2|pages=159–163|doi=10.1038/s41567-018-0318-2|arxiv=1803.04402|s2cid=125264133|issn=1745-2473}}</ref>}}

{{term|[[Quantum Turing machine]]}}
{{defn|(QTM), or universal quantum computer, is an [[abstract machine]] used to model the effects of a [[quantum computer]].  It provides a simple model that captures all of the power of quantum computation—that is, any [[quantum algorithm]] can be expressed formally as a particular quantum Turing machine. However, the computationally equivalent [[quantum circuit]] is a more common model.<ref name=equivalence>{{cite conference|author=Andrew Yao|author-link=Andrew Yao|title=Quantum circuit complexity|conference=34th Annual Symposium on Foundations of Computer Science|pages=352–361|year=1993}}</ref><ref name="newequivalence">{{cite journal|arxiv=1808.01701|author1=Abel Molina|author2=John Watrous|author-link2=John Watrous (computer scientist)|title=Revisiting the simulation of quantum Turing machines by quantum circuits|journal=Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences|date=2018|volume=475|issue=2226|doi=10.1098/rspa.2018.0767|pmid=31293355|pmc=6598068}}</ref>{{rp|2}}}}

{{term|[[Qubit]]}}
{{defn|A qubit ({{IPAc-en|ˈ|k|juː|b|ɪ|t}}) or '''quantum bit''' is a basic unit of [[quantum information]]—the quantum version of the classic binary [[bit]] physically realized with a two-state device. A qubit is a [[Two-state quantum system|two-state (or two-level) quantum-mechanical system]], one of the simplest quantum systems displaying the peculiarity of quantum mechanics.  Examples include the [[Spin (physics)|spin]] of the electron in which the two levels can be taken as spin up and spin down; or the [[Photon polarization|polarization]] of a single [[photon]] in which the two states can be taken to be the vertical polarization and the horizontal polarization. In a classical system, a bit would have to be in one state or the other. However, quantum mechanics allows the qubit to be in a coherent [[Quantum superposition|superposition]] of both states simultaneously, a property that is fundamental to [[quantum mechanics]] and [[quantum computing]].}}

{{term|[[Quil (instruction set architecture)]]}}
{{defn| is a [[quantum computing|quantum]] [[instruction set architecture]] that first introduced a shared quantum/classical memory model. It was introduced by Robert Smith, Michael Curtis, and William Zeng in ''A Practical Quantum Instruction Set Architecture''.<ref name=":0">{{cite arXiv|last1=Smith|first1=Robert S.|last2=Curtis|first2=Michael J.|last3=Zeng|first3=William J.|date=2016-08-10|title=A Practical Quantum Instruction Set Architecture|eprint=1608.03355|class=quant-ph}}</ref>  Many [[quantum algorithm]]s (including [[quantum teleportation]], [[quantum error correction]], simulation,<ref>{{Cite journal|last1=McClean|first1=Jarrod R.|last2=Romero|first2=Jonathan|last3=Babbush|first3=Ryan|last4=Aspuru-Guzik|first4=Alán|date=2016-02-04|title=The theory of variational hybrid quantum-classical algorithms|arxiv=1509.04279|journal=New Journal of Physics|volume=18|issue=2|pages=023023|doi=10.1088/1367-2630/18/2/023023|issn=1367-2630|bibcode=2016NJPh...18b3023M|s2cid=92988541}}</ref><ref>{{cite arXiv|last=Rubin|first=Nicholas C.|date=2016-10-21|title=A Hybrid Classical/Quantum Approach for Large-Scale Studies of Quantum Systems with Density Matrix Embedding Theory|eprint=1610.06910|class=quant-ph}}</ref> and optimization algorithms<ref>{{cite arXiv|last1=Farhi|first1=Edward|last2=Goldstone|first2=Jeffrey|last3=Gutmann|first3=Sam|date=2014-11-14|title=A Quantum Approximate Optimization Algorithm|eprint=1411.4028|class=quant-ph}}</ref>) require a [[shared memory architecture]]. Quil is being developed for the superconducting quantum processors developed by [[Rigetti Computing]] through the Forest [[Cloud-based quantum computing|quantum programming API]].<ref>{{Cite web|url=https://spectrum.ieee.org/rigetti-launches-fullstack-quantum-computing-service-and-quantum-ic-fab|title=Rigetti Launches Full-Stack Quantum Computing Service and Quantum IC Fab|website=IEEE Spectrum: Technology, Engineering, and Science News|date=26 June 2017|language=en|access-date=2017-07-06}}</ref><ref>{{Cite web|url=https://quantumcomputingreport.com/news/rigetti-quietly-releases-beta-of-forest-platform-for-quantum-programming-in-the-cloud/|title=Rigetti Quietly Releases Beta of Forest Platform for Quantum Programming in the Cloud {{!}} Quantum Computing Report|website=quantumcomputingreport.com|date=8 March 2017|language=en-US|access-date=2017-07-06}}</ref>  A [[Python (programming language)|Python]] library called <code>pyQuil</code> was introduced to develop Quil programs with higher level constructs. A Quil [[front and back ends|backend]] is also supported by other quantum programming environments.<ref>{{Cite web|url=https://ornl-qci.github.io/xacc/accelerators/rigetti|title=XACC Rigetti Accelerator|website=ornl-qci.github.io|access-date=2017-07-06|archive-date=2017-12-01|archive-url=https://web.archive.org/web/20171201032840/https://ornl-qci.github.io/xacc/accelerators/rigetti|url-status=dead}}</ref><ref>{{Citation|last=Doiron|first=Nick|title=jsquil: Quantum computer instructions for JavaScript developers|date=2017-03-07|url=https://github.com/mapmeld/jsquil|access-date=2017-07-06}}</ref>}}

{{term|[[Qutrit]]}}
{{defn|(or '''quantum trit'''), is a unit of [[quantum information]] that is realized by a 3-level quantum system, that may be in a [[Quantum superposition|superposition]] of three mutually orthogonal [[quantum states]].<ref>{{Cite journal|last1=Nisbet-Jones|first1=Peter B. R.|last2=Dilley|first2=Jerome|last3=Holleczek|first3=Annemarie|last4=Barter|first4=Oliver|last5=Kuhn|first5=Axel|date=2013|title=Photonic qubits, qutrits and ququads accurately prepared and delivered on demand|url=http://stacks.iop.org/1367-2630/15/i=5/a=053007|journal=New Journal of Physics|language=en|volume=15|issue=5|pages=053007|doi=10.1088/1367-2630/15/5/053007|issn=1367-2630|arxiv=1203.5614|bibcode=2013NJPh...15e3007N|s2cid=110606655 }}</ref>

The qutrit is analogous to the classical [[radix]]-3 [[trit (computing)|trit]], just as the [[qubit]], a quantum system described by a superposition of two orthogonal states, is analogous to the classical radix-2 [[bit]].

There is ongoing work to develop quantum computers using qutrits and qubits with multiple states.<ref name="urlFull Page Reload">{{cite web |url=https://spectrum.ieee.org/qudits-the-real-future-of-quantum-computing |title=Qudits: The Real Future of Quantum Computing? |date=28 June 2017 |publisher=[[IEEE Spectrum]] |access-date=2021-05-24}}</ref>}}

{{term|[[Solovay–Kitaev theorem]]}}
{{defn|In quantum information and computation, the Solovay–Kitaev theorem says, roughly, that if a set of single-[[qubit]] [[quantum gate]]s generates a [[Dense subset|dense]] [[subset]] of [[SU(2)]] then that set is guaranteed to fill SU(2) quickly, which means any desired gate can be approximated by a fairly short sequence of gates from the generating set. [[Robert M. Solovay]] initially announced the result on an email list in 1995, and [[Alexei Kitaev]] independently gave an outline of its proof in 1997.<ref name="KY97">{{Cite journal|last=Kitaev|first=A Yu|date=1997-12-31|title=Quantum computations: algorithms and error correction|url=http://dx.doi.org/10.1070/rm1997v052n06abeh002155|journal=Russian Mathematical Surveys|volume=52|issue=6|pages=1191–1249|doi=10.1070/rm1997v052n06abeh002155|bibcode=1997RuMaS..52.1191K |s2cid=250816585 |issn=0036-0279}}</ref> Solovay also gave a talk on his result at [[Mathematical Sciences Research Institute|MSRI]] in 2000 but it was interrupted by a fire alarm.<ref name="RS00">{{Cite AV media|last=Solovay|first=Robert|date=2000-02-08|title=Lie Groups and Quantum Circuits|url=https://www.msri.org/workshops/189/schedules/12826|publisher=MSRI}}</ref> Christopher M. Dawson and [[Michael Nielsen]] call the theorem one of the most important fundamental results in the field of [[Quantum computing|quantum computation]].<ref name="DN06">{{Cite journal|last1=Dawson|first1=Christopher M.|last2=Nielsen|first2=Michael|date=2006-01-01|title=The Solovay-Kitaev algorithm|url=https://dl.acm.org/doi/abs/10.5555/2011679.2011685|journal=Quantum Information & Computation|volume=6|pages=81–95|doi=10.26421/QIC6.1-6|language=EN|arxiv=quant-ph/0505030}}</ref>}}

{{glossaryend}}

== References ==
{{Reflist|30em}}

== Further reading ==
{{Refbegin|2}}
===Textbooks===
* {{cite book |last=Aaronson |first=Scott |author-link=Scott Aaronson |title=Quantum Computing Since Democritus |date=2013 |publisher=Cambridge University Press |isbn=978-0-521-19956-8 |oclc=829706638 |doi=10.1017/CBO9780511979309 }}
* {{cite book |last=Akama |first=Seiki |year=2014 |title=Elements of Quantum Computing: History, Theories and Engineering Applications |publisher=Springer |isbn=978-3-319-08284-4 |oclc=884786739 |doi=10.1007/978-3-319-08284-4 }}
* {{cite book |last1=Benenti |first1=Giuliano |last2=Casati |first2=Giulio |last3=Rossini |first3=Davide |last4=Strini |first4=Giuliano |title=Principles of Quantum Computation and Information: A Comprehensive Textbook |edition=2nd |year=2019 |isbn=978-981-3237-23-0 |oclc=1084428655 |doi=10.1142/10909 |s2cid=62280636 }}
* {{cite book |last=Bernhardt |first=Chris |year=2019 |title=Quantum Computing for Everyone |publisher=MIT Press |oclc=1082867954 |isbn=978-0-262-35091-4 }}
* {{cite book |last=Hidary |first=Jack D. |year=2021 |edition=2nd |title=Quantum Computing: An Applied Approach |oclc=1272953643 |isbn=978-3-03-083274-2 |doi=10.1007/978-3-030-83274-2 |s2cid=238223274 }}
* {{cite book |editor-last1=Hiroshi |editor-first1=Imai |editor-last2=Masahito |editor-first2=Hayashi |year=2006 |title = Quantum Computation and Information: From Theory to Experiment |series=Topics in Applied Physics |volume=102 |isbn=978-3-540-33133-9 |doi=10.1007/3-540-33133-6 }}
* {{cite book |last1=Hughes |first1=Ciaran |last2=Isaacson |first2=Joshua |last3=Perry |first3=Anastasia |last4=Sun |first4=Ranbel F. |last5=Turner |first5=Jessica |title=Quantum Computing for the Quantum Curious |isbn=978-3-03-061601-4 |oclc=1244536372 |doi=10.1007/978-3-030-61601-4 |year=2021 |s2cid=242566636 |url=https://link.springer.com/content/pdf/10.1007/978-3-030-61601-4.pdf }}
* {{cite book |last=Jaeger |first=Gregg |title=Quantum Information: An Overview |year=2007 |isbn=978-0-387-36944-0 |oclc=186509710 |doi=10.1007/978-0-387-36944-0 }}
* {{cite book |last1=Johnston |first1=Eric R. |last2=Harrigan |first2=Nic |last3=Gimeno-Segovia |first3=Mercedes |title=Programming Quantum Computers: Essential Algorithms and Code Samples |year=2019 |publisher=O'Reilly Media, Incorporated |oclc=1111634190 |isbn=978-1-4920-3968-6 }}
* {{cite book |last1=Kaye |first1=Phillip |last2=Laflamme |first2=Raymond |last3=Mosca |first3=Michele |author-link2=Raymond Laflamme |author-link3=Michele Mosca |title=An Introduction to Quantum Computing |year=2007 |publisher=OUP Oxford |oclc=85896383 |isbn=978-0-19-857000-4 }}  
* {{cite book |last1=Kitaev |first1=Alexei Yu. |author-link1=Alexei Kitaev |last2=Shen |first2=Alexander H. |last3=Vyalyi |first3=Mikhail N. |title=Classical and Quantum Computation |year=2002 |publisher=American Mathematical Soc. |oclc=907358694 |isbn=978-0-8218-3229-5 }}
* {{cite book |last1=Mermin |first1=N. David |author1-link=N. David Mermin |title=Quantum Computer Science: An Introduction |date=2007 |isbn=978-0-511-34258-5 |oclc=422727925 |doi=10.1017/CBO9780511813870 }}
* {{cite book |doi=10.17226/25196 |title=Quantum Computing : Progress and Prospects |date=2019 |editor-first1=Emily |editor-last1=Grumbling |editor-first2=Mark |editor-last2=Horowitz |author=[[National Academies of Sciences, Engineering, and Medicine]] |isbn=978-0-309-47970-7 |location=Washington, DC |s2cid=125635007 |oclc=1091904777}}
* {{cite book | author1-link= Michael Nielsen| last1=Nielsen |first1=Michael |author2-link =  Isaac L. Chuang |last2=Chuang |first2=Isaac |title=[[Quantum Computation and Quantum Information]] |year=2010 |edition=10th anniversary |isbn=978-0-511-99277-3 |oclc= 700706156 |doi=10.1017/CBO9780511976667 | s2cid=59717455 }}
* {{cite book |last1=Stolze |first1=Joachim |last2=Suter |first2=Dieter |year=2004 |title =Quantum Computing: A Short Course from Theory to Experiment |isbn =978-3-527-61776-0 |oclc=212140089 |doi=10.1002/9783527617760 }}
* {{cite book |last=Wichert |first=Andreas |year=2020 |title=Principles of Quantum Artificial Intelligence: Quantum Problem Solving and Machine Learning |edition=2nd |doi=10.1142/11938 |isbn=978-981-12-2431-7 |s2cid=225498497 |oclc=1178715016 }}
* {{cite book |last=Wong |first=Thomas |title=Introduction to Classical and Quantum Computing |publisher=Rooted Grove |year=2022 |isbn=979-8-9855931-0-5 |oclc=1308951401 |url=http://www.thomaswong.net/introduction-to-classical-and-quantum-computing-1e.pdf |access-date=2022-08-29 |archive-date=2022-01-29 |archive-url=https://web.archive.org/web/20220129214631/http://www.thomaswong.net/introduction-to-classical-and-quantum-computing-1e.pdf |url-status=dead }}
* {{cite book |last1=Zeng |first1=Bei |last2=Chen |first2=Xie |last3=Zhou |first3=Duan-Lu |last4=Wen |first4=Xiao-Gang |title=Quantum Information Meets Quantum Matter |year=2019 |oclc=1091358969 |isbn=978-1-4939-9084-9 |doi=10.1007/978-1-4939-9084-9 |arxiv=1508.02595 |s2cid=118528258 }}

===Academic papers===
*{{cite journal | author1-link=Derek Abbott |last1=Abbot |first1=Derek |author2-link= Charles R. Doering |last2=Doering |first2=Charles R. |author3-link= Carlton M. Caves |last3=Caves |first3=Carlton M. |author4-link=Daniel Lidar |last4=Lidar |first4=Daniel M. |author5-link= Howard Brandt|last5=Brandt |first5=Howard E. |author6-link= Alexander R. Hamilton |last6=Hamilton |first6=Alexander R. |author7-link=David K. Ferry |last7=Ferry |first7=David K. |author8-link=Julio Gea-Banacloche |last8=Gea-Banacloche |first8=Julio |author9-link=Sergey M. Bezrukov |last9=Bezrukov |first9=Sergey M. |author10-link=Laszlo B. Kish |first10=Laszlo B. |last10=Kish | title=Dreams versus Reality: Plenary Debate Session on Quantum Computing |journal=Quantum Information Processing |year=2003 |volume=2 |issue=6 |pages=449–472 |doi=10.1023/B:QINP.0000042203.24782.9a | arxiv=quant-ph/0310130 |bibcode=2003QuIP....2..449A |hdl=2027.42/45526|s2cid=34885835 }}
*{{cite web |last=Berthiaume |first=Andre |year=1997 |title=Quantum Computation |url=http://citeseer.ist.psu.edu/article/berthiaume97quantum.html }}
*{{Cite journal |last1=DiVincenzo |first1=David P. |author1-link=David DiVincenzo |title=The Physical Implementation of Quantum Computation|journal=Fortschritte der Physik|volume=48|issue=9–11|pages=771–783|year=2000|doi=10.1002/1521-3978(200009)48:9/11<771::AID-PROP771>3.0.CO;2-E |arxiv=quant-ph/0002077 |bibcode=2000ForPh..48..771D|s2cid=15439711 }}
*{{cite journal |last=DiVincenzo |first=David P. |title=Quantum Computation |journal=Science |year=1995 |volume=270 |issue=5234 |pages=255–261 |doi= 10.1126/science.270.5234.255 |bibcode = 1995Sci...270..255D |citeseerx=10.1.1.242.2165 |s2cid=220110562 }} Table 1 lists switching and dephasing times for various systems.
*{{cite journal |last=Feynman |first=Richard |author-link=Richard Feynman |title=Simulating physics with computers |journal=International Journal of Theoretical Physics |volume=21 |pages=467–488 |year=1982 |doi = 10.1007/BF02650179 |bibcode = 1982IJTP...21..467F | issue=6–7 |citeseerx=10.1.1.45.9310 |s2cid=124545445 }}
*{{cite journal |last=Jeutner |first=Valentin |title=The Quantum Imperative: Addressing the Legal Dimension of Quantum Computers |journal=Morals & Machines |volume=1 |pages=52–59 |year=2021 |doi=10.5771/2747-5174-2021-1-52 |issue=1 |s2cid=236664155 |url=https://lup.lub.lu.se/record/e034e7b7-d17c-4863-9cee-7e654f97225b |doi-access=free }}
*{{cite web |last=Mitchell |first=Ian |year=1998 |title=Computing Power into the 21st Century: Moore's Law and Beyond |url=http://citeseer.ist.psu.edu/mitchell98computing.html }}
*{{cite web |last = Simon |first = Daniel R. |year = 1994 |title = On the Power of Quantum Computation |publisher = Institute of Electrical and Electronics Engineers Computer Society Press |url = http://citeseer.ist.psu.edu/simon94power.html }}
{{Refend}}

{{Quantum computing}}
{{emerging technologies|quantum=yes|other=yes}}
{{Computer science}}
{{Quantum mechanics topics}}
{{Glossaries of computers}}
{{Glossaries of science and engineering}}

[[Category:Models of computation]]
[[Category:Quantum cryptography]]
[[Category:Information theory]]
[[Category:Computational complexity theory]]
[[Category:Classes of computers]]
[[Category:Theoretical computer science]]
[[Category:Open problems]]
[[Category:Glossaries of technology|Quantum computing]]
[[Category:Wikipedia glossaries using description lists]]