Optimal unambiguous comparison of two unknown squeezed vacua
Stefano Olivares, Michal Sedlák, Peter Rapčan, Matteo G. A. Paris, Vladimír Bužek · Physical Review A · 2011
We propose a scheme for the unambiguous state comparison (USC) of two unknown squeezed vacuum states of the electromagnetic field. Our setup is based on linear optical elements and photon-number detectors, and it achieves optimal USC in an ideal case of unit quantum efficiency. In realistic conditions, i.e., for nonunit quantum efficiency of photodetectors, we evaluate the probability of getting an ambiguous result as well as the reliability of the scheme, thus showing its robustness in comparison to previous proposals.