Minimum-error discrimination of entangled quantum states

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.

4 pages, 4 figures

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• Optimal sequential measurements for bi-partite state discrimination
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• Bipartite quantum state discrimination and decomposable entanglement witness
• Violating the Modified Helstrom Bound with Nonprojective Measurements
• Minimal-error quantum state discrimination versus robustness of entanglement:More indistinguishability with less entanglement
• Unbounded entanglement-sustaining sequential local quantum state discrimination