Patent ID: 8238556

Claim:
A quantum communication system comprising a sending unit and a receiving unit, said sending unit comprising a photon source assembly configured to output a stream of pulses of light with each pulse having one of at least two different intensities and a memory configured to store information for determining which pulses should be reference pulses and which pulses should be data pulses, the average intensity of reference pulses being different to the average intensity of data pulses, said reference pulse multiplexed in time with said data pulses, wherein the number of reference pulses per unit time differs from the number of signal pulses per unit time, the receiving unit comprising a memory for storing information for identifying the position of reference pulses within the stream of pulses and a processor for determining the calibration of the quantum communication system from the reference pulses, wherein the sending unit and the receiving unit are configured to share information for determining the position in the stream of pulses of light of the reference pulses and the data pulses before the stream of pulses of light is output by the sending unit.