Continuous-variable quantum key distribution under strong channel polarization disturbance

Wenyuan Liu, Yanxia Cao, Xuyang Wang, and Yongmin Li
Phys. Rev. A 102, 032625 – Published 25 September 2020

Abstract

In a commercial fiber-based quantum key distribution (QKD) system, the state of polarization (SOP) of the optical fields is inevitably disturbed by random birefringence of the standard single-mode fiber due to an external complex environment. We analyze theoretically the effect of SOP fluctuations on the continuous-variable (CV) QKD system and experimentally verify its validity. To overcome the influence of the polarization variations, a self-adaptive gradient algorithm is proposed to achieve high-speed polarization controlling under pulsed light with field programmable gate array hardware. For single random polarization scrambling, the polarization extinction ratio achieved is over 30 dB and the average time of polarization control is 827 μs. In order to eliminate further the effect of the occasional failures of polarization control, we properly filter the raw keys in terms of the relative phase fluctuations between the signal and the local oscillator. By combining this approach with the high-speed polarization control, we demonstrate a CV QKD under a continuous polarization scrambling of 314 rad/s. Our results provide useful references for practical application of fiber-based CV QKD in a field environment.

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  • Received 20 February 2020
  • Accepted 2 September 2020

DOI:https://doi.org/10.1103/PhysRevA.102.032625

©2020 American Physical Society

Physics Subject Headings (PhySH)

Quantum Information, Science & Technology

Authors & Affiliations

Wenyuan Liu, Yanxia Cao, Xuyang Wang, and Yongmin Li*

  • State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006, People's Republic of China and Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, People's Republic of China

  • *yongmin@sxu.edu.cn

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Issue

Vol. 102, Iss. 3 — September 2020

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