Abstract: A method for polarization compensation includes: (a) generating at least one beam of an electromagnetic wave; (b) sending the at least one beam through a physical medium; (c) receiving the at least one beam of an electromagnetic wave after it has traversed the physical medium; (d) measuring the intensity of the electromagnetic wave after it traverses a system of electromagnetic retarders; (e) determining the polarization of the electromagnetic wave after it traverses the system of electromagnetic retarders; (f) calculating the positions of the electromagnetic retarders to match the determined polarization of the electromagnetic wave with the polarization of the generated electromagnetic wave; and (g) compensating the effect of the physical medium on the polarization of the electromagnetic wave by setting the electromagnetic retarders according to the calculated positions.

Abstract: A method for Quantum Communication, including the steps: obtaining, by a detector, a base signal, wherein the base signal includes an indication of a background optical noise of a communication channel; determining, based on the obtained base signal, a width of a time gate value; applying to the detector the determined width of time gate; and obtaining a QKD signal including QKD signal pulses sent through the communication channel by applying the time gate having the determined width for filtering the background optical noise. A corresponding optical receiver, QKD pulse stream and QKD system for quantum communication are also provided.

Abstract: A method for Quantum Communication, including the steps: obtaining, by a detector, a base signal, wherein the base signal includes an indication of a background optical noise of a communication channel; determining, based on the obtained base signal, a width of a time gate value; applying to the detector the determined width of time gate; and obtaining a QKD signal including QKD signal pulses sent through the communication channel by applying the time gate having the determined width for filtering the background optical noise. A corresponding optical receiver, QKD pulse stream and QKD system for quantum communication are also provided.

Abstract: A method for polarization compensation includes: (a) generating at least one beam of an electromagnetic wave; (b) sending the at least one beam through a physical medium; (c) receiving the at least one beam of an electromagnetic wave after it has traversed the physical medium; (d) measuring the intensity of the electromagnetic wave after it traverses a system of electromagnetic retarders; (e) determining the polarization of the electromagnetic wave after it traverses the system of electromagnetic retarders; (f) calculating the positions of the electromagnetic retarders to match the determined polarization of the electromagnetic wave with the polarization of the generated electromagnetic wave; and (g) compensating the effect of the physical medium on the polarization of the electromagnetic wave by setting the electromagnetic retarders according to the calculated positions.