Apparatus and method for enhancing secret key rate exchange over quantum channel in quantum key distribution systems

A method for enhancing secret key rate exchange over quantum channel in a QKD system based on weak coherent pulses with an emitter system and a predetermined number of receiver systems each connected via a transmission system with the emitter system, the method comprising:

• setting a predetermined loss value for the emitter system,
• setting a predetermined loss value for every one of the number of receiver systems,
• determining a highest loss value for said number of receiver systems if there is more than one receiver system involved,
• setting a predetermined loss value for the transmission system,
• defining a first quantum channel loss budget based on the distance to be covered between the quantum emitter and one of the quantum receivers and the infrastructure properties of the quantum channel,
• defining a second quantum channel loss budget, wherein the second quantum channel loss budget is associated to the loss within the realm of the emitter system,
• computing an optimal mean number of photons of coherent states to be emitted by the emitter system based on first and second quantum channel loss budgets,
• computing expected detection probabilities at the involved receiver system, and
• running a key exchange between said emitter system and the involved receiver system.