Implementing nonprojective measurements via linear optics: An approach based on optimal quantum-state discrimination
- National Institute of Informatics, 2-1-2 Hitotsubashi, Chiyoda-ku, Tokyo 101-8430 (Japan)
- Quantum Information Theory Group, Institute of Theoretical Physics I, Institute of Optics, Information and Photonics (Max-Planck Forschungsgruppe), Universitaet Erlangen-Nuernberg, Staudtstr. 7, D-91058 Erlangen (Germany)
We discuss the problem of implementing generalized measurements [positive operator-valued measures (POVMs)] with linear optics, either based upon a static linear array or including conditional dynamics. In our approach, a given POVM shall be identified as a solution to an optimization problem for a chosen cost function. We formulate a general principle: the implementation is only possible if a linear-optics circuit exists for which the quantum mechanical optimum (minimum) is still attainable after dephasing the corresponding quantum states. The general principle enables us, for instance, to derive a set of necessary conditions for the linear-optics implementation of the POVM that realizes the quantum mechanically optimal unambiguous discrimination of two pure nonorthogonal states. This extends our previous results on projection measurements and the exact discrimination of orthogonal states.
- OSTI ID:
- 20787466
- Journal Information:
- Physical Review. A, Vol. 73, Issue 6; Other Information: DOI: 10.1103/PhysRevA.73.062320; (c) 2006 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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