# Portal:Quantum computing

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## Quantum computing

**Quantum computing** studies computation systems (**quantum computers**) that make direct use of quantum-mechanical phenomena, such as superposition and entanglement, to perform operations on data.^{[1]} Quantum computers are different from binary digital electronic computers based on transistors. Whereas common digital computing requires that the data be encoded into binary digits (bits), each of which is always in one of two definite states (0 or 1), quantum computation uses quantum bits, which can be in superpositions of states. A quantum Turing machine is a theoretical model of such a computer, and is also known as the universal quantum computer. The field of quantum computing was initiated by the work of Paul Benioff^{[2]} and Yuri Manin in 1980,^{[3]} Richard Feynman in 1982,^{[4]} and David Deutsch in 1985.^{[5]} A quantum computer with spins as quantum bits was also formulated for use as a quantum spacetime in 1968.^{[6]}

As of 2017^{[update]}, the development of actual quantum computers is still in its infancy, but experiments have been carried out in which quantum computational operations were executed on a very small number of quantum bits.^{[7]} Both practical and theoretical research continues, and many national governments and military agencies are funding quantum computing research in additional effort to develop quantum computers for civilian, business, trade, environmental and national security purposes, such as cryptanalysis.^{[8]} A small 16-qubit quantum computer exists and is available for hobbyists to experiment with via the *IBM quantum experience* project. Along with the IBM computer a company called D-Wave has also been developing their own version of a quantum computer that uses a process called annealing.^{[9]}

Large-scale quantum computers would theoretically be able to solve certain problems much more quickly than any classical computers that use even the best currently known algorithms, like integer factorization using Shor's algorithm or the simulation of quantum many-body systems. There exist quantum algorithms, such as Simon's algorithm, that run faster than any possible probabilistic classical algorithm.^{[10]} A classical computer could in principle (with exponential resources) simulate a quantum algorithm, as quantum computation does not violate the Church–Turing thesis.^{[11]}^{:13–16} On the other hand, quantum computers may be able to efficiently solve problems which are not *practically* feasible on classical computers.

### References

**^**Gershenfeld, Neil; Chuang, Isaac L. (June 1998). "Quantum Computing with Molecules" (PDF).*Scientific American*.**^**Benioff, Paul (1980). "The computer as a physical system: A microscopic quantum mechanical Hamiltonian model of computers as represented by Turing machines".*Journal of statistical physics*.**22**(5): 563–591. Bibcode:1980JSP....22..563B. doi:10.1007/BF01011339.**^**Manin, Yu. I. (1980).*Vychislimoe i nevychislimoe*[*Computable and Noncomputable*] (in Russian). Sov.Radio. pp. 13–15. Retrieved 2013-03-04.**^**Feynman, R. P.u (1982). "Simulating physics with computers".*International Journal of Theoretical Physics*.**21**(6): 467–488. Bibcode:1982IJTP...21..467F. doi:10.1007/BF02650179.**^**Deutsch, David (1985). "Quantum Theory, the Church-Turing Principle and the Universal Quantum Computer".*Proceedings of the Royal Society of London A*.**400**(1818): 97–117. Bibcode:1985RSPSA.400...97D. CiteSeerX 10.1.1.144.7936 . doi:10.1098/rspa.1985.0070.**^**Finkelstein, David (1968). "Space-Time Structure in High Energy Interactions". In Gudehus, T.; Kaiser, G.*Fundamental Interactions at High Energy*. New York: Gordon & Breach.**^**Gershon, Eric (2013-01-14). "New qubit control bodes well for future of quantum computing". Phys.org. Retrieved 2014-10-26.**^**Quantum Information Science and Technology Roadmap for a sense of where the research is heading.**^**Explaining the upside and downside of D-Wave's new Quantum computer**^**Simon, D.R. (1994). "On the power of quantum computation".*Foundations of Computer Science, 1994 Proceedings., 35th Annual Symposium on*: 116–123. CiteSeerX 10.1.1.655.4355 . doi:10.1109/SFCS.1994.365701. ISBN 0-8186-6580-7.**^**Chuang, Michael A. Nielsen & Isaac L. (2001).*Quantum computation and quantum information*(Repr. ed.). Cambridge [u.a.]: Cambridge Univ. Press. ISBN 978-0521635035.

## Selected article

The **DiVincenzo criteria** are a list of conditions that are necessary for constructing a quantum computer proposed by the theoretical physicist David P. DiVincenzo in his 2000 paper "The Physical Implementation of Quantum Computation".^{[1]} Quantum computation was first proposed by Yuri Manin^{[2]} (1980) and Richard Feynman^{[3]} (1982) as a means to efficiently simulate quantum systems. There have been many proposals of how to construct a quantum computer, all of which have varying degrees of success against the different challenges of constructing quantum devices. Some of these proposals involve using superconducting qubits, trapped ions, liquid and solid state nuclear magnetic resonance or optical cluster states all of which have remarkable prospects, however, they all have issues that prevent practical implementation. The DiVincenzo criteria are a list of conditions that are necessary for constructing the quantum computer as proposed by Feynman.

The DiVincenzo criteria consist of 5+2 conditions that an experimental setup must satisfy in order to successfully implement quantum algorithms such as Grover's search algorithm or Shor factorisation. The 2 additional conditions are necessary in order to implement quantum communication such as that used in quantum key distribution. One can consider DiVincenzo's criteria for a classical computer and demonstrate that these are satisfied. Comparing each statement between the classical and quantum regimes highlights both the complications that arise in dealing with quantum systems and the source of the quantum speed up.

## Selected biography

Quantum computing | |
---|---|

Born | Yuri Ivanovitch Manin February 16, 1937 Simferopol, Soviet Union |

Residence | Germany |

Nationality | Russia |

Alma mater | Moscow State University Steklov Mathematics Institute (PhD) |

Known for | algebraic geometry, diophantine geometry |

Awards | Nemmers Prize in Mathematics (1994) Schock Prize (1999) Cantor Medal (2002) Bolyai Prize (2010) King Faisal International Prize (2002) |

Scientific career | |

Fields | Mathematician |

Institutions | Max-Planck-Institut für Mathematik Northwestern University |

Doctoral advisor | Igor Shafarevich |

Doctoral students | Alexander Beilinson, Vladimir Drinfeld, Victor Kolyvagin, Vyacheslav Shokurov, Alexei Skorobogatov |

**Yuri Ivanovitch Manin** (Russian: Ю́рий Ива́нович Ма́нин; born 1937) is a Soviet/Russian/German^{[4]} mathematician, known for work in algebraic geometry and diophantine geometry, and many expository works ranging from mathematical logic to theoretical physics. Moreover, Manin was one of the first to propose the idea of a quantum computer in 1980 with his book "Computable and Uncomputable".^{[2]}

## In the news

Google has recently created a program called OpenFermion to help generate the appropriate algorithm for a quantum computer to simulate a chemical molecule. The program is open source and available on GitHub. It is meant to allow chemists to solve their problems without having an extensive knowledge of quantum computing, or vice versa. Microsoft announced a similar project in September, though not nearly as many details were given, and their project was not open source. People are encouraged to contribute to the OpenFermion GitHub repository.

## Selected picture

**The page "Portal:Quantum computing/Selected picture/3" does not exist.**

## Did you know?

- ...that Google has announced that it expects to achieve
**quantum supremacy**by the end of 2017, and IBM says that the best classical computers will be beaten on some task within about five years? - ...that one of the greatest challenges in building a quantum computer is controlling or removing
**quantum decoherence**? - ...that there are many quantum computing models, including one where photons are the qubits and quantum gates are represented by
**linear optical components**?

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**^**DiVincenzo, David P. (2000-04-13). "The Physical Implementation of Quantum Computation".*Fortschritte der Physik*.**48**: 771–783. arXiv:quant-ph/0002077 [quant-ph]. doi:10.1002/1521-3978(200009)48:9/11<771::AID-PROP771>3.0.CO;2-E.- ^
^{a}^{b}Manin, Yu. I. (1980).*Vychislimoe i nevychislimoe*[*Computable and Noncomputable*] (in Russian). Sov.Radio. pp. 13–15. Retrieved 2013-03-04. Cite error: Invalid`<ref>`

tag; name "manin1980vychislimoe" defined multiple times with different content (see the help page). **^**Feynman, R. P. (June 1982). "Simulating physics with computers".*International Journal of Theoretical Physics*.**21**(6): 467–488. Bibcode:1982IJTP...21..467F. doi:10.1007/BF02650179.**^**"Archived copy" (PDF). Archived from the original (PDF) on May 14, 2009. Retrieved July 15, 2008. CURRICULUM VITAE at Max-Planck-Institut für Mathematik website