Position determination of the phase modulator in the Sagnac interferometer used in quantum key distribution systems

Stepanov K.V., Borisova A.V., Vtyurina A.G.

For Russian citation (Opticheskii Zhurnal):

Степанов К.В., Борисова А.В., Втюрина А.Г. Оценка положения фазового модулятора в интерферометре Саньяка, используемого в системах квантового распределения ключей // Оптический журнал. 2025. Т. 92. № 9. С. 55–61. http://doi.org/10.17586/1023-5086-2025-92-09-55-61

Stepanov K.V., Borisova A.V., Vtyurina A.G. Position determination of the phase modulator in the Sagnac interferometer used in quantum key distribution systems [in Russian] // Opticheskii Zhurnal. 2025. V. 92. № 9. P. 55–61. http://doi.org/10.17586/1023-5086-2025-92-09-55-61

For citation (Journal of Optical Technology):

Abstract:

Subject of study. Phase modulation device for encoding quantum states based on an electro-optical phase modulator asymmetrically located in a Sagnac interferometer. Aim of study. Development of a technologically advanced and repeatable method for measuring the path difference to a phase modulator inside a Sagnac interferometer in quantum key distribution systems. Method. A phase difference in the splitter forming the Sagnac interferometer is created between clockwise and counterclockwise continuous propagating radiation when an electrical pulse is applied to the phase modulator. Moreover, a single electrical pulse creates an optical phase difference twice due to the phase modulator asymmetric location. Main results. A method for measuring the radiation propagation time difference in counter directions to a phase modulator, placed in a Sagnac interferometer, which can be used for simultaneous modulation of phase and intensity in quantum key distribution systems, has been proposed and experimentally tested. Practical significance. The results of a high-precision technological method for measuring the radiation propagation time difference in counter directions to an asymmetrically installed in a Sagnac interferometer phase modulator obtained in the research are relevant for the production of optoelectronic modules of quantum key distribution systems, where this value directly affects the quality of the systems and their performance in general.

Keywords:

quantum key distribution, phase modulation, Sagnac interferometer

OCIS codes: 060.5060, 060.5565, 270.5568

References:

1. Zbinden H., Bechmann-Pasquinucci H., Gisin N., et al. Quantum cryptography // Appl. Phys. B. 1988. V. 67. P. 743–748. https://doi.org/10.1007/s003400050574
2. Кулик С.П., Молотков С.Н., Маккавеев А.П. Комбинированный фазово-временной метод кодирования в квантовой криптографии // Письма в ЖЭТФ. 2007. Т. 85. № 6. С. 354–359.
Kulik S.P., Molotkov S.N., Makkaveev A.P. Combined phase-time encoding method in quantum cryptography // JETP Lett. 2007. V. 85. P. 297–301. https://doi.org/10.1134/S0021364007060070
3. Молотков С.Н. Аналог дифференциально-фазовой квантовой криптографии на когерентных состояниях с доказуемой криптографической стойкостью // Письма в ЖЭТФ. 2015. Т. 102. № 6. С. 436–443. https://doi.org/10.7868/S0370274X15180150
Molotkov S.N. Analog of differential-phase quantum cryptography on coherent states with provable cryptographic security // JETP Lett. 2015. V. 102. P. 396–403. https://doi.org/10.1134/S0021364015180095
4. Qi B., Huang L.L., Lo H.K., et al. Quantum key distribution based on a Sagnac loop interferometer and polarization-insensitive phase modulators // IEEE Intern. Symp. Inform. Theory. Washington, USA. July 9–14, 2006. P. 2090–2093. https://doi.org/10.1109/ISIT.2006.261919
5. Roberts G.L., Pittaluga M., Minder M., et al. Patterning-effect mitigating intensity modulator for secure decoy-state quantum key distribution // Opt. Lett. 2018. V. 43. P. 5110–5113. https://doi.org/10.1364/OL.43.005110
6. Tang Y., Dong J. Sagnac interferometer-based time phase coding device and quantum key distribution system // EP Patent 3 823 208 A1. 2019. Publ. May 19, 2021.
7. Алферов С.В., Паргачев И.А. Способ и устройство генерации квантовых состояний в системе квантового распределения ключей с фазовым кодированием // Патент РФ № RU2777422C1. Бюл. 2022. № 22.
Alferov S.V., Pargachev I.A. Method and device for generating quantum states in phase-coded quantum key distribution system // RF Patent № RU2777422C1. Bull. 2022. № 22.
8. Zhirnov A.A., Choban T.V., Stepanov K.V., et al. Distributed acoustic sensor using a double Sagnac interferometer based on wavelength division multiplexing // Sensors. 2022. V. 22. № 7. P. 2772. https://doi.org/10.3390/s22072772
9. Dakin J.P., Pearce D.A.J., Strong A.P., et al. A novel distributed optical fibre sensing system enabling location of disturbances in a Sagnac loop interferometer // Fiber Optic and Laser Sensors V. SPIE, 1988. V. 838. P. 325–328. https://doi.org/10.1117/12.942527