F. E. Becerra Chavez, J. Fan, G. Baumgartner, J. Goldhar, J. Kosloski, and A. Migdall, "Beating the Standard Quantum Limit for Nonorthogonal Multi-State Discrimination,"
in CLEO: 2013,
OSA Technical Digest (online)
(Optical Society of America, 2013), paper QF2B.4.
We demonstrate a quantum receiver that discriminates four nonorthogonal states with error probabilities below the standard quantum limit (SQL) for a wide range of input powers and as much as 6 dB below the SQL.