  A M-ary phase shift keying (PSK) quantum receiver consisting of displacement
operations, photon counting, and electrical feed-back adaptive measurements is
analyzed with a realistic model considering the effects of the sub-unity
quantum efficiency and the dark counts of single-photon detectors, as well as
the transmittance and the mode mismatch of beam splitters. Among these factors,
the mode mismatch has the greatest impact on the error probability of the
receiver with on-off detectors. The errors due to mode mismatch can be
suppressed effectively by using photon-number-resolving detectors (PNRD)
instead of on-off detectors.
