We investigate a strategy for M-ary discrimination of nonorthogonal phase states with error rates below the homodyne limit. This strategy uses feed forward to update a reference ﬁeld and Signal nulling for the state discrimination. We experimentally analyze the receiver performance using postprocessing and a Bayesian strategy to emulate the feed-forward process. This analysis demonstrates that for a moderate system detection eﬃciency, it is possible to surpass the homodyne error limit for quadrature phase-shift keying (QPSK) signals using feed forward.
Citation: Physical Review A
Pub Type: Journals
state discrimination, quantum information, quantum communication, single photon, quantum mechanics, single photon detection