Quantum process

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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.

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<span class="mw-page-title-main">Karl Kraus (physicist)</span> German theoretical physicist

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Quantum foundations is a discipline of science that seeks to understand the most counter-intuitive aspects of quantum theory, reformulate it and even propose new generalizations thereof. Contrary to other physical theories, such as general relativity, the defining axioms of quantum theory are quite ad hoc, with no obvious physical intuition. While they lead to the right experimental predictions, they do not come with a mental picture of the world where they fit.

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References

  1. Pechukas, Philip (1994). "Reduced Dynamics Need Not Be Completely Positive". Physical Review Letters. 73 (8): 1060–1062. Bibcode:1994PhRvL..73.1060P. doi:10.1103/PhysRevLett.73.1060. ISSN   0031-9007. PMID   10057614.
  2. Shaji, Anil; Sudarshan, E.C.G. (2005). "Who's afraid of not completely positive maps?". Physics Letters A. 341 (1–4). Elsevier BV: 48–54. Bibcode:2005PhLA..341...48S. doi:10.1016/j.physleta.2005.04.029. ISSN   0375-9601.