This activity analysed the feasibility and performance of the quantum pulse gate (QPG) technique for noise rejection in optical communication systems. The optical frequency band is expected to play an increasingly important role in space communications due to a substantial increase in available data rates with respect to radio transmission, as well as enhanced information security. The main limiting factor for the performance of an optical link is the background noise collected by the receiver, especially when operated at low signal powers, e.g. in the photon-starved regime typical to deep space communication and quantum key distribution protocols with single photons.

The conventional technique of narrowband spectral filtering of the received signal followed by temporal gating does not allow one to select in a lossless manner the signal mode from the remaining background noise. On the other hand, the recently demonstrated quantum pulse gate technique allows for genuine single-mode filtering, accomplished by carefully engineered sum-frequency generation in a (2) nonlinear optical medium. In the context of communication, the technique may then be used to separate the single information-carrying mode of a received signal beam from the remaining modes containing only unwanted noise. The activity presents a careful consideration of this prospect, in which was concluded the noise reduction capabilities of the QPG to be promising for free-space optical link enhancement.