Method for quantum communication

A method for quantum communication between at least three receivers in a network system, the network system comprising a source, a frequency multiplexer, the at least three receivers and a network of quantum channels, wherein the method comprises the following steps:

• i) generating an entangled photon pair in the source with a signal photon and an idler photon, wherein the signal photon is generated in a signal wavelength range and the idler photon is generated in an idler wavelength range;
• ii) assigning the signal and idler photons to the quantum channels in the frequency multiplexer on the basis of their wavelength;
• iii) transmitting the photon pair to the receivers via the quantum channels;
• iv) detecting the photon pair at the receivers for the quantum communication,
• wherein the photons generated in step i) are generated in a signal wavelength range and an idler wavelength range that are spectrally separated from one another, and
• wherein, in step ii), the photons are assigned to the quantum channels such that, in step iii), only signal photons are transmitted to a first receiver for the communication with all other receivers, and, in step iii), only idler photons are transmitted to a second receiver for the communication with all other receivers, and, in step iii), both signal photons and idler photons are transmitted to the further receivers for the communication with all other receivers, and
• wherein all receivers are connected to the source via in each case one quantum channel.