Quantum key distribution system, quantum key distribution method and quantum key distribution program
A transmission device ( 1 ) includes a modulation unit ( 14 ) that modulates photons with a predetermined data pattern, a synchronization signal generation unit ( 12 ) that generates a frame synchronization signal of a random number data pattern, an identification signal generation unit ( 13 ) that divides the frame into a plurality of subframes and generate a subframe identification signal indicating a subframe, and a transmission unit ( 17 ) that transmits the photons modulated by the modulation unit ( 14 ), the frame synchronization signal, and the subframe identification signal. A reception device ( 2 ) includes a reception unit ( 30 ) that receives the photons, the frame synchronization signal, and the subframe identification signal transmitted from the transmission unit ( 17 ), a decoding unit ( 21 ) that detects and decodes a data pattern from the photons, a time measurement unit ( 26 ) that measures an elapsed time from the subframe identification signal until a photon is detected in each subframe, and a detection time calculation unit ( 27 ) that calculates a photon detection time from the frame synchronization signal to photon detection in one frame, based on the elapsed time.
1 . A quantum key distribution system comprising one or more computers for performing operations for distributing a quantum key between a transmission device and a reception device, the operations comprising:
at the transmission device:
modulating photons output from a light source unit with a predetermined data pattern;
generating a frame synchronization signal indicating a position of a frame of a random number data pattern;
dividing the frame into a plurality of subframes and generate a subframe identification signal indicating a subframe; and
transmitting the modulated photons, the frame synchronization signal, and the subframe identification signal, and
at the reception device:
receiving the modulated photons, the frame synchronization signal, and the subframe identification signal transmitted by the transmission device;
decoding a data pattern from the received modulated photons;
measuring an elapsed time from the subframe identification signal until a photon is detected in each subframe; and
calculating a photon detection time from the frame synchronization signal to photon detection in one frame, based on the elapsed time.
2 . The quantum key distribution system according to claim 1 , wherein the operations further comprise:
at the reception device, after measuring the elapsed time from the subframe identification signal, storing the elapsed time in a storage device, and
reading the elapsed time stored in the storage device before calculating the photon detection time.
3 . The quantum key distribution system according to claim 1 ,
wherein the frame synchronization signal and the subframe identification signal are transmitted as an optical signal having a wavelength different from a wavelength of the photon.
4 . The quantum key distribution system according to claim 1 ,
wherein the subframe identification signal includes a predetermined number of bits at a head of the frame synchronization signal.
5 . The quantum key distribution system according to claim 1 ,
wherein the subframe identification signal is superimposed on the frame synchronization signal.
6 . A quantum key distribution method for distributing a quantum key between a transmission device and a reception device, the method comprising:
at the transmission device, a step of modulating photons output from a light source unit with a predetermined data pattern;
a step of generating a frame synchronization signal indicating a position of a frame of a random number data pattern;
a step of dividing the frame into a plurality of subframes and generating a subframe identification signal indicating a subframe; and
a step of transmitting the modulated photons, the frame synchronization signal, and the subframe identification signal; and
at the reception device, a step of receiving the modulated photons, the frame synchronization signal, and the subframe identification signal transmitted from the transmission device;
a step of decoding a data pattern from the received modulated photons;
a step of measuring an elapsed time from the subframe identification signal until a photon is detected in each subframe; and
a step of calculating a photon detection time from the frame synchronization signal to photon detection in one frame, based on the elapsed time.
7 . A non-transitory computer-readable storage medium storing a quantum key distribution program for causing a computer to perform operations for distributing a quantum key between a transmission device and a reception device, the operations comprising:
at the transmission device, a step of modulating photons output from a light source unit with a predetermined data pattern;
a step of generating a frame synchronization signal indicating a position of a frame of a random number data pattern;
a step of dividing the frame into a plurality of subframes and generating a subframe identification signal indicating a subframe; and
a step of transmitting the modulated photons, the frame synchronization signal, and the subframe identification signal; and
at the reception device, a step of receiving the modulated photons, the frame synchronization signal, and the subframe identification signal transmitted from the transmission device;
a step of decoding a data pattern from the received modulated photons;
a step of measuring an elapsed time from the subframe identification signal until a photon is detected in each subframe; and
a step of calculating a photon detection time from the frame synchronization signal to photon detection in one frame, based on the elapsed time.