Optimum unambiguous discrimination of two mixed quantum states
- Institut fuer Physik, Humboldt-Universitaet Berlin, Newtonstrasse 15, D-12489 Berlin (Germany)
- Department of Physics, Hunter College, City University of New York, 695 Park Avenue, New York, New York 10021 (United States)
We investigate generalized measurements, based on positive-operator-valued measures, and von Neumann measurements for the unambiguous discrimination of two mixed quantum states that occur with given prior probabilities. In particular, we derive the conditions under which the failure probability of the measurement can reach its absolute lower bound, proportional to the fidelity of the states. The optimum measurement strategy yielding the fidelity bound of the failure probability is explicitly determined for a number of cases. One example involves two density operators of rank d that jointly span a 2d-dimensional Hilbert space and are related in a special way. We also present an application of the results to the problem of unambiguous quantum state comparison, generalizing the optimum strategy for arbitrary prior probabilities of the states.
- OSTI ID:
- 20717699
- Journal Information:
- Physical Review. A, Vol. 71, Issue 5; Other Information: DOI: 10.1103/PhysRevA.71.050301; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1050-2947
- Country of Publication:
- United States
- Language:
- English
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