Minimum-error discrimination of entangled quantum states

TL;DR

This paper demonstrates an experimental method for optimally distinguishing entangled quantum states using local measurements and feed-forward, achieving the Helstrom bound and outperforming non-feed-forward schemes.

Contribution

It introduces a practical optical implementation for minimum-error discrimination of entangled states using only local measurements and feed-forward, aligning with the Helstrom bound.

Findings

Achieves perfect discrimination of orthogonal states.

Attains minimum error discrimination of non-orthogonal states.

Shows advantage over schemes without feed-forward.

Abstract

Strategies to optimally discriminate between quantum states are critical in quantum technologies. We present an experimental demonstration of minimum error discrimination between entangled states, encoded in the polarization of pairs of photons. Although the optimal measurement involves projecting onto entangled states, we use a result of Walgate et al. to design an optical implementation employing only local polarization measurements and feed-forward, which performs at the Helstrom bound. Our scheme can achieve perfect discrimination of orthogonal states and minimum error discrimination of non-orthogonal states. Our experimental results show a definite advantage over schemes not using feed-forward.