Encoding information in quantum systems and sending it through a communication channel permits to improve state-of-the-art classical protocols in the reception, and the security of the signal. At the transmitter, we can place a laser source that produces a train of quantum states, and we can modulate the phase of these pulses performing the so called Phase Shift Keying (PSK) modulation. It has been shown that the error probability of an optical transmission system encoding information in quantum states can significantly improve the performance with respect to the analogue classical optical transmission.

Quantum communications have been implemented for the first time at the Jet Propulsion Laboratory , in the effort of improving the communication data rates of the Deep Space Network, which is progressively moving to the optical wavelength domain.