Abstract: Strategies to optimally discriminate between quantum states are critical in quantum technologies. We present an experimental demonstration of minimum-error discrimination between [...]]]> Our paper Minimum-error discrimination of entangled quantum states by Yang Lu, Nick Coish, Rainer Kaltenbaek, Deny Hamel, Sarah Croke, and Kevin Resch was published today in Physical Review A.

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 projection onto entangled states, we use a result of J. Walgate et al. [Phys. Rev. Lett. 85, 4972 (2000)] 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 nonorthogonal states.  Our experimental results show a definite advantage over schemes not using feed-forward.