Optimal unambiguous comparison of two unknown squeezed vacua

TL;DR

This paper introduces an optimal linear optical scheme for unambiguously comparing two unknown squeezed vacuum states, demonstrating robustness under realistic detector efficiencies.

Contribution

It presents a novel, optimal method for unambiguous comparison of unknown squeezed vacua using linear optics and photon detectors, with performance analysis under non-ideal conditions.

Findings

Achieves optimal unambiguous state comparison in ideal conditions.

Evaluates scheme robustness with non-unit detector efficiency.

Shows improved reliability over previous methods.

Abstract

We propose a scheme for unambiguous state comparison (USC) of two unknown squeezed vacuum states of an electromagnetic field. Our setup is based on linear optical elements and photon-number detectors, and achieves optimal USC in an ideal case of unit quantum efficiency. In realistic conditions, i.e., for non-unit 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.