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arXiv:2303.11549 · Journal of Lightwave Technology

Simple and Fast Polarization Tracking Algorithm for Continuous-Variable Quantum Key Distribution System Using Orthogonal Pilot Tone

Yan Pan, Heng Wang, Yun Shao, Yaodi Pi, Ting Ye, Shuai Zhang, Yang Li, Wei Huang, Bingjie Xu

Published May 19, 2023• 16 citations
arXivHTMLPDF

Abstract

To reduce the influence of random channel polarization variation, especially fast polarization perturbation, for continuous-variable quantum key distribution (CV-QKD) systems, a simple and fast polarization tracking algorithm is proposed and experimentally demonstrated. The algorithm is implemented by an orthogonal pilot tone scheme, one of the pilot tones is used for estimating the polarization rotation angle, and the other one is used for compensating the polarization perturbation introduced phase noise. Meanwhile, residual effects are compensated precisely with the help of a real-valued FIR filter. In this case, the excess noise introduced by polarization perturbation is effectively suppressed. Experimental results show that the polarization scrambling rate ≥12.57 krad/s can be tracked by using the proposed algorithm, and a good estimated parameters performance is achieved. Compared to conventional polarization tracking algorithms such as the constant modulus algorithm (CMA), experimental results show that the polarization tracking capability of the proposed algorithm is significantly improved. Furthermore, much faster polarization tracking performance is evaluated by digital simulations, and the simulation results show that about 188.50 Mrad/s can be tracked by the proposed algorithm. Thus, our method provides effective technology for the practical application of fiber-based CV-QKD.

DOI
10.1109/jlt.2023.3277982

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In this article, we propose a pilot alternately assisted scheme of orthogonal dual-polarization and time multiplexing for the local local oscillator continuous-variable quantum key distribution (LLO CV-QKD). Our scheme utilizes time multiplexing and dual-polarization multiplexing techniques to dramatically isolate the quantum signal from the pilot light. To analyze the influence mechanism of time-domain diffusion and polarization perturbation on the key parameters, such as the channel transmittance and excess noise, of the studied system, a general LLO excess noise model based on polarization extinction ratio (PER) and time-domain pulse extinction ratio (TER) is established. We mainly focus on the photon-leakage noise from the reference path to the quantum signal path, which is first analyzed in the dual polarization LLO regime. Furthermore, we conduct a series of simulations to verify the proposed dual polarization and time multiplexing model. Results show that it maintains a low level of excess noise and a secure key rate (SKR) of 10.25 Mbps@25km can be obtained under the finite-size effect. We achieved 0.93Mbps@25km SKR under a relatively low PER of 17 dB in the nanosecond level pulse width. Our work greatly extends the application scenarios of the dual-polarization division multiplexing CV-QKD system and provides a theoretical and representative framework for the study of improving the performance of the dual-polarization CV-QKD system.
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