Quantum key distribution system, quantum key distribution method and quantum key distribution program

Patent metadata

Field	Value
Publication number	US-12512972-B2
Application number	US-202118688429-A
Country	US
Kind code	B2
Filing date	Sep 1, 2021
Priority date	Sep 1, 2021
Publication date	Dec 30, 2025
Grant date	Dec 30, 2025

Abstract

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.

First claim

The invention claimed is:

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.

Assignees

• Ntt Inc

Inventors

• Taniguchi Atsushi
• Takahashi Hirokazu
• Nishizawa Hideki

Classifications

• H04B10/85 Primary

  Protection from unauthorised access, e.g. eavesdrop protection · CPC title

• H04L9/0852 Primary

  Quantum cryptography (transmission systems employing electromagnetic waves other than radio waves, e.g. light, infrared H04B10/00; wavelength-division multiplex systems H04J14/02; WDM arrangements H04J14/03) · CPC title

• H04L9/08

  Key distribution {or management, e.g. generation, sharing or updating, of cryptographic keys or passwords (network architectures or network communication protocols for supporting key management in a packet data network H04L63/06)} · CPC title

• H04L9/12

  Transmitting and receiving encryption devices synchronised or initially set up in a particular manner · CPC title