Quantum communication system and a quantum communication method

A quantum communication method for communicating over a system comprising a receiver unit, the receiver unit comprising a source of classical signals and the receiver unit further comprising a quantum receiver, the quantum receiver comprising at least one detector configured to detect quantum signals;

• the system further comprising a plurality of transmitter units, each transmitter unit comprising a detector configured to detect classical signals and each transmitter unit further comprising a source of quantum signals;
• and the system further comprising a passive optical splitter, wherein the plurality of transmitter units are optically coupled to the receiver unit through the passive optical splitter;
• the method comprising the steps of:
• sending quantum signals from the plurality of transmitter units to the passive optical splitter;
• distributing the quantum signals into a first spatial channel and a second spatial channel, wherein the first spatial channel and second spatial channel are separate spatial channels, irrespective of a wavelength of the quantum signals;
• receiving the quantum signals from the first spatial channel at the quantum receiver;
• sending a classical signal from the receiver unit to the passive optical splitter through the second spatial channel;
• distributing the classical signal to the plurality of transmitter units, irrespective of a wavelength of the classical signal;
• wherein the passive optical splitter is optically coupled to the quantum receiver through the first spatial channel and optically coupled to a first classical communication device through the second spatial channel, and wherein the passive optical splitter is configured such that the first spatial channel is optically coupled through the passive optical splitter to a plurality of spatial channels and the second separate spatial channel is optically coupled through the passive optical splitter to the same plurality of spatial channels.