METHOD FOR QUANTUM ENCODING AND TRANSMISSION OF CRYPTOGRAPHIC KEYS Russian patent published in 2014 - IPC H04L9/08 G02B26/00 

FIELD: radio engineering, communication.

SUBSTANCE: quantum cryptographic system not only enables to detect any attempts at intruding into a communication channel, but also guarantees unconditional secrecy of transmitted cryptographic keys under the condition that an error at a receiving station in primary keys does not exceed a certain critical value. The method involves generating polarisation states at a receiving/transmitting station for a series of classic synchronising laser pulses using a polarisation controller in one arm of an interferometer and a polarisation controller at the output of the interferometer, which facilitate interference balancing of the interferometer; after reflection from a mirror in a transformation station, a series of single-photon states is detected at the transmitting/receiving station and the obtained photocount statistics are used to calculate the permissible error, which is then compared with a certain error threshold to obtain a cryptographic key known only at the transmitting/receiving and transformation stations.

EFFECT: wider range of possible distortions of polarisation of laser and single-photon pulses when transmitting keys between transmitting/receiving and transformation stations, in which is guaranteed the secrecy of cryptographic keys and the lifting of the condition of using a special Faraday mirror.

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