Binary optical communication in single-mode and entangled quantum noisy channels

We address binary optical communication in single-mode and entangled quantum noisy channels. For single mode we present a systematic comparison between direct photodetection and homodyne detection in realistic conditions, i.e. taking into account the noise that occurs during both the propagation and the detection of the signals. We then consider entangled channels based on a twin-beam state of radiation, and show that with realistic heterodyne detection the error probability at fixed channel energy is reduced in comparison with the single-mode cases for a large range of values of quantum efficiency and noise parameters.