M -ary-state phase-shift-keying discrimination below the homodyne limit
F. E. Becerra, Jingyun Fan, Gerald Baumgartner, Sergey V. Polyakov, J. Goldhar, Jon T. Kosloski, Alan L. Migdall · Physical Review A · 2011
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 shows that for a moderate system detection efficiency, it is possible to surpass the homodyne error limit for quadrature phase-shift keying signals using feed forward.