Quantum computing

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The quantum computer science or quantum information processing is the science of an information processing , the quantum mechanical uses phenomena. New perspectives are seen. In this way, some calculations could be carried out much faster than is possible with a classic computer . Quantum informatics is counted among the quantum technologies .

Classical information processing always uses a large number of macroscopic particles to represent a state. Although the individual particles are subject to quantum mechanical laws, their quantum mechanical characteristics can be neglected for macroscopically large particles due to the correspondence principle.

Especially in institute names, but occasionally also in other linguistic usage, the research area quantum informatics is also referred to with its research object, i.e. quantum information .

Theoretical foundations

Analogous to the bit in classical information, there is also a smallest unit in quantum information, the qubit . This is a quantum mechanical two-level system.

In quantum informatics, the quantum properties of a system of qubits are used. In addition to the superposition , this is especially the entanglement , which can be interpreted as the interference of different basic states.

Due to the complementarity principle and the related quantum mechanical uncertainty relation , the state of qubits cannot be read out completely. Rather, each reading of a qubit leads to a collapse of the wave function , so that ultimately only one classic bit is read. For this reason, quantum algorithms generally work probabilistically, i.e. H. a run only delivers the desired result with a certain (as high as possible) probability.

Communication is an important topic in quantum computing. Information is sent via quantum channels between nodes of a quantum network. One possibility for transmission is the use of quantum teleportation , in which two quanta are entangled to form a common quantum physical state. Even if they are separated, they remain connected to each other over long distances. Albert Einstein had described the effect as a ghostly long-range effect . This could make tap-proof, extremely fast networks possible. The secure encryption of sent messages is carried out by quantum cryptography , but could also be used to network quantum computers .

Quantum computer

The goal of quantum informatics is the development of a quantum computer. Thanks to quantum parallelism , such a system could compute certain tasks, for which a classic computer would take a long time, in a much shorter time. An example of the extreme acceleration in solving certain problems is the Shor algorithm for the decomposition of the product of two prime numbers into its factors. This algorithm is particularly relevant because the security of the widespread RSA encryption method is based precisely on the difficulty of this decomposition.

Quantum computers work in a similar way to classical computers with discrete operations that only affect a limited number of qubits. Such operations are called quantum gates .

One problem in the development of quantum computers is decoherence , which converts quantum states into classical random distributions. To compensate for these, special error correction methods are required that manage without measuring the qubits, because this measurement in turn would destroy the quantum state. These methods are known as quantum error correction .

See also


  • Dagmar Bruß: Quantum Information . Fischer Taschenbuch Verlag, Frankfurt am Main 2015, ISBN 978-3-596-30422-6 .
  • Matthias Homeister: Understanding Quantum Computing . 5th edition. Springer / Vieweg, Wiesbaden 2018, ISBN 978-3-658-22883-5 .
  • B. Lenze: Mathematics and Quantum Computing . 2nd Edition. Logos Verlag, Berlin 2020, ISBN 978-3-8325-4716-5 .
  • RJ Lipton, KW Regan: Quantum Algorithms via Linear Algebra: A Primer . MIT Press, Cambridge MA 2014, ISBN 978-0-262-02839-4 (English).
  • Wolfgang Scherer: Mathematics of Quantum Informatics . Springer Spectrum, Berlin / Heidelberg 2016, ISBN 978-3-662-49079-2 .
  • Wolfgang Tittel, Jürgen Brendel, Nicolas Gisin, Grégoire Ribordy, Hugo Zbinden: Quantum Cryptography . In: Physical sheets . tape 55 , no. 6 , 1999, p. 25 , doi : 10.1002 / phbl.19990550608 .
  • RF Werner: Quantum Information Theory - an invitation . In: Quantum Information - An Introduction to Basic Theoretical Concepts and Experiments (=  Springer Tracts in Modern Physics ). Springer, 2001, doi : 10.1007 / 3-540-44678-8_2 , arxiv : quant-ph / 0101061 (English).
  • CP Williams: Explorations in Quantum Computing . 2nd Edition. Springer-Verlag, London 2011, ISBN 978-1-84628-886-9 (English).

Web links

Individual evidence

  1. Fraunhofer FOKUS Competence Center Public IT: The ÖFIT trend sonar in IT security - quantum communication. April 2016, accessed May 20, 2016 .