Demonstration of Optimal Non-Projective Measurement of Binary Coherent States*

Quantum state discrimination is a central problem in quantum measurement theory, with applications spanning from quantum communication to computation. Quantum mechanics allows for the realization of optimized measurements based on photon counting for the discrimination of nonorthogonal coherent states able to surpass the conventional limits of detection, such as the homodyne and heterodyne limits. Such measurements have a large potential for increasing sensitivities and information transfer in communications and for information processing. In this talk I will describe our current work in the problem of generalized measurements for coherent state discrimination.  We implement an optimal inconclusive measurement for binary coherent states [1], a non-projective measurement that allows for achieving the lowest probability of error for a given rate of inconclusive results. This measurement encompasses standard measurement paradigms for state discrimination, specifically minimum error and unambiguous discrimination, and allows to transition between them in an optimal way.

 

[1] K. Nakahira and T. S. Usuda, Phys.Rev.A 86, 052323 (2012).