Abstract: A method of key distribution, a key distribution system, a single photon source system and a method of generating single photons. The method of key distribution comprises the steps of: providing a free space optics, FSO, link between a transmitter and a receiver; detecting whether an eavesdropper is present along the FSO link; transmitting individual photons or weak coherent pulses, as an approximation of individual photons, each encoding a basic unit of the key according to a binary or higher number base system from the transmitter to the receiver; and comparing timing information associated with the transmission and reception of the individual photons for determining the key when it is detected that no eavesdropper is present along the FSO link.

Abstract: A method and circuit for operating a liquid crystal device, LCD, based polarisation rotator. The method comprises the steps of tracking a capacitance value of the LCD rotator; and controlling a driver setting to the LCD rotator based on the tracked capacitance value to achieve temperature independent operation.

Abstract: A random number generator, RNG, a method of fabricating the same, and a method of generating a random number. The RNG, comprises at least one first avalanche photodiode, APD, configured for producing “1” events based on dark electron initiated avalanches in the first APD; at least one second avalanche photodiode, APD, configured for producing “0” events based on dark electron initiated avalanches in the second APD; and a feedback circuit configured for substantially evening out the respective numbers of generated avalanches in the first and second APDs by independently controlling respective dynamic bias voltages of the first and second APDs.

Abstract: A method of key distribution, a key distribution system, a single photon source system and a method of generating single photons. The method of key distribution comprises the steps of: providing a free space optics, FSO, link between a transmitter and a receiver; detecting whether an eavesdropper is present along the FSO link; transmitting individual photons or weak coherent pulses, as an approximation of individual photons, each encoding a basic unit of the key according to a binary or higher number base system from the transmitter to the receiver; and comparing timing information associated with the transmission and reception of the individual photons for determining the key when it is detected that no eavesdropper is present along the FSO link.

Abstract: A random number generator, RNG, a method of fabricating the same, and a method of generating a random number. The RNG, comprises at least one first avalanche photodiode, APD, configured for producing “1” events based on dark electron initiated avalanches in the first APD; at least one second avalanche photodiode, APD, configured for producing “0” events based on dark electron initiated avalanches in the second APD; and a feedback circuit configured for substantially evening out the respective numbers of generated avalanches in the first and second APDs by independently controlling respective dynamic bias voltages of the first and second APDs.

Abstract: A method and circuit for operating a liquid crystal device, LCD, based polarisation rotator. The method comprises the steps of tracking a capacitance value of the LCD rotator; and controlling a driver setting to the LCD rotator based on the tracked capacitance value to achieve temperature independent operation.