# Portal:Quantum computing

## 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

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## Selected biography

Peter Shor | |
---|---|

Born | New York City, New York, U.S. | August 14, 1959

Residence | United States |

Nationality | American |

Alma mater | Caltech Massachusetts Institute of Technology |

Known for | Shor's algorithm |

Awards | Putnam Fellow (1978)^{[1]}Nevanlinna Prize (1998) ^{[2]}MacArthur Fellowship (July 1999) ^{[3]}Gödel Prize (1999) ^{[4]}King Faisal International Prize (2002) ^{[5]}ICS Prize (2007) ^{[6]}Dirac Medal (2017) of ICTP ^{[7]} |

Scientific career | |

Fields | Computer scientist |

Institutions | Massachusetts Institute of Technology Bell Labs University of California, Berkeley |

Doctoral advisor | Tom Leighton |

**Peter Williston Shor** (born August 14, 1959) is an American professor of applied mathematics at MIT. He is known for his work on quantum computation, in particular for devising Shor's algorithm, a quantum algorithm for factoring exponentially faster than the best currently-known algorithm running on a classical computer.

## 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

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## 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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**^**"The Mathematical Association of America's William Lowell Putnam Competition". Mathematical Association of America. Retrieved 2007-02-12.**^**"Fields Medalists / Nevanlinna Price (sic) Winner 1998". International Mathematical Union. 2006-08-22. Retrieved 2010-09-26.**^**"Fellows List - July 1999". John D. and Catherine T. MacArthur Foundation. Archived from the original on 2006-09-28. Retrieved 2007-02-12.**^**Parberry, Ian (1999-05-10). "1999 Gödel Prize". ACM SIGACT. Retrieved 2007-02-12.**^**"2002 King Faisal International Prizes for Science Announced". King Faisal Foundation.**^**"ICS Prize".**^**Dirac Medal of ICTP 2017