Beating the standard quantum limit for binary phase-shift-keying discrimination with a hybrid feed-forward receiver

We propose a hybrid feed-forward receiver (HFFRE) for the discrimination of binary phase-shift-keyed coherent states based on the appropriate combination of the displacement feed-forward receiver (DFFRE) and a homodyne-like setup employing a low-intensity local oscillator and photon-number-resolving detectors. We investigate the performance of the proposed scheme addressing also realistic scenarios in the presence of non-unit quantum detection efficiency, dark counts and a visibility reduction. The present HFFRE outperforms the DFFRE in all conditions, beating the standard quantum limit in particular regimes.Comment: 10 pages, 10 figure