Quantum process

In quantum mechanics, a quantum process is a somewhat ambiguous term which usually refers to the time evolution of an (open) quantum system. Under very general assumptions, a quantum process is described by the quantum operation formalism (also known as a quantum dynamical map), which is a linear, trace-preserving, and completely positive map from the set of density matrices to itself.

For instance, in quantum process tomography, the unknown quantum process is assumed to be a quantum operation.

However, not all quantum processes can be captured within the quantum operation formalism;[1][2] in principle, the density matrix of a quantum system can undergo completely arbitrary time evolution.

References

  1. ↑ Philip Pechukas, "Reduced Dynamics Need Not Be Completely Positive", Phys. Rev. Lett. 73, 1060 (1994).
  2. ↑ Anil Shaji and E.C.G. Sudarshan "Who's Afraid of not Completely Positive Maps?", Physics Letters A Volume 341, 20 June 2005, Pages 48–54
  • Nielsen, Michael A.; Chuang, Isaac L. (2010). Quantum Computation and Quantum Information (2nd ed.). Cambridge: Cambridge University Press. ISBN 978-1-107-00217-3. OCLC 844974180.


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