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; in principle, the density matrix of a quantum system can undergo completely arbitrary time evolution.
References
- 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.
- 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.
- 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.
 | This quantum mechanics-related article is a stub. You can help Misplaced Pages by expanding it. |