Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Physical Review A

Continuous-variable quantum key distribution under strong channel polarization disturbance

Wenyuan Liu, Yanxia Cao, Xuyang Wang, Yongmin Li

Published Sep 25, 2020• 37 citations
Publisher

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 $\ensuremath{\mu}\mathrm{s}$. 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.

DOI
10.1103/physreva.102.032625

Related papers

Research on dynamic polarization control in continuous variable quantum key distribution systems

Guangwei Zhang, Jiandong Bai, Qi Jie +3 more

In a commercial fiber-based quantum key distribution system, the local and signal optical fields are transmitted through long distance fibers by using time division multiplexing and polarization multiplexing. The state of polarization of the optical field is inevitably disturbed by random birefringence of the standard single-mode fiber caused by external complex environments. This drift of the state of polarization significantly affects the balanced homodyne detection results and the secret key rate. Therefore, the key technology of the dynamic polarization control unit is crucial for the system in a large-scale commercial application. We theoretically analyze and prove that the polarization control unit only needs the combination of two degrees of freedom when considering the result of an arbitrary polarization extinction ratio at the receiver of the system. To overcome the influence of polarization variations, we propose a chaotic monkey algorithm based on Bayesian parameter estimation method and implement intelligence algorithm on field programmable gate array (FPGA) hardware under pulsed light with an integral-type detector for the dynamic polarization control unit. The simulation results show that the optimal combination is four degrees of freedom and the optimal prior distribution is an exponential distribution among various distributions in the dynamic polarization control unit. According to the simulation results, the experimental results show that the achieved polarization extinction ratio is over 30 dB and the average time of polarization control is 400 μs for a single random polarization scrambling. By combining the dynamic polarization control unit with the system, we demonstrate the continuous variable quantum key distribution (CV-QKD) under a continuous polarization scrambling scope of 0－2 krad/s and verify its effectiveness. In addition, the methods presented will improve the performance of the system and expand the range of applications even under strong external disturbance.

Acta Physica Sinica•Jan 1, 2024•3 citations

Continuous-variable quantum key distribution robust against environmental disturbances

Huanxi Zhao, Tao Wang, Yuehan Xu +5 more

Continuous variable quantum key distribution (CV-QKD) can guarantee that two parties share secure keys even in the presence of an eavesdropper. However, the polarization direction of the coherent state transmitted in CV-QKD is susceptible to environmental disturbances during channel transmission, making it difficult to share keys consistently over long periods of time. Therefore, a CV-QKD system that can resist environmental disturbance is very urgent. In this paper, we propose a new optical architecture for CV-QKD based on the Faraday-Michelson interference (FMI) structure, and finally form an all-single-mode (SM) fiber-based stable CV-QKD system which employs transmitted local oscillator (TLO) scheme and discrete modulation coherent state (DMCS) protocol. Specifically, since the Faraday mirror rotates the polarization direction of light by 90 o , the birefringence effect of light can be effectively dealt with, thus ensuring the same polarization state of light before and after reflection. The final simulation results show that the theoretical secret key rate of this scheme can reach 139 kbps at 70 km, which can further improve the stability and robustness of CV-QKD in the real environment, and provide technical support for the next-generation high-stability QKD system.

Optics Express•Jan 17, 2024•8 citations

Robustness of continuous variable quantum key distribution under strong polarization drift

Margarida Almeida, Armando N. Pinto, Nuno A. Silva

Abstract The practical deployment of Continuous Variables Quantum Key Distribution (CV-QKD) systems benefits from existing optical fiber telecommunication infrastructures. However, optical fibers introduce random variations in the state of polarization, which degrades the system's performance.We consider a CV-QKD system featuring a polarization diversity heterodyne receiver and the constant modulus algorithm (CMA) to compensate for the polarization drifts in the quantum channel. Our setup can effectively realign Alice's quantum signal with Bob's local oscillator for polarization drift variances below \(10^{-10}\) .This value is compatible with most experimental implementations, allowing for accurate estimation of the channel transmission and excess noise parameters. This validates the approximation of real-world implementations under polarization drift to an ideal scenario without polarization drift, ensuring that the security proof remains applicable for polarization drift variances below $ 10^{-10} $.Our results establish operational limits for passive polarization drift compensation using a polarization diversity receiver combined with digital CMA.This enables long-term stability in \linebreak CV-QKD systems, eliminating the need for active polarization controllers and manual adjustments.

EPJ Quantum Technology•Oct 15, 2025•0 citations

Polarization-state tracking based on Kalman filter in continuous-variable quantum key distribution

Tao Wang, Peng Huang, Shiyu Wang +1 more

Continuous-variable quantum key distribution with a real local oscillator (LO) has been extensively studied recently due to its security and simplicity. Making it operate automatically and resistant to channel interference is the key to further long-term system operation. To overcome the dynamic changes in the state of polarization (SOP) of quantum signal caused by the random birefringence effect in fiber, Kalman filter is employed to estimate the polarization misalignment, thereby achieving polarization demultiplexing at the data level, and ultimately recovering the quantum signal with the help of a two-step phase compensation. The signal transmission and processing is simulated, which verifies the SOP tracking ability and the immunity to the fast phase drift. A proof-of-principle experiment is also conducted, and results show that it can resist the interference of SOP rotation at 1 krad/s, and has the ability to distribute 8.4 kbps secret key rate within 20 km when only considering SOP tracking imperfection, confirming its feasibility under harsh channel conditions.

Optics Express•Sep 9, 2019•26 citations

Experimental Demonstration of LLO Continuous-Variable Quantum Key Distribution With Polarization Loss Compensation

Tao Shen, Xiangyu Wang, Ziyang Chen +3 more

The compensation process for the state of polarization (SOP) from quantum signal plays an important role in the practical implementation of continuous-variable quantum key distribution (CV-QKD). In contrast to the previous scheme using an expensive digital dynamic polarization controller, we choose a cheaper manual polarization controller interfaced with a digital algorithm based on Kalman filter to achieve compensation of the polarization loss under the condition that the SOP of the fiber is relatively stable. This paper also enumerates the details of other digital signal processing method to achieve final secret key rate. And a pilot-sequential Gaussian modulated coherent state (GMCS) continuous-variable quantum key distribution system with a local local oscillator (LLO) is experimentally implemented based on the analysis of excess noise. Finally, the experimental results show that the method of polarization loss compensation takes advantages in maintaining the stability of the final secret key rate. And a secret key rate of 110 kbps is achieved within 20 km optical fiber (with 4 dB loss) under the finite-size block of$1 \times {10^{6}}$during a more extended time in the laboratory.

IEEE photonics journal•Feb 20, 2023•17 citations

An Orthogonal Dual-Polarization and Time Multiplexing Scheme of Continuous-Variable Quantum Key Distribution

Shuai Zhang, Yan Pan, Heng Wang +8 more

In this article, we propose a time and orthogonal polarization division multiplexing scheme for local local oscillator continuous-variable quantum key distribution (LLO CV-QKD) system. According to the influence mechanism of time-domain diffusion and polarization disturbance on the key parameters, such as the channel transmittance and excess noise, of the studied system, we established a dual-polarization theoretical model and verified its validity by simulations. Here, the pulse width at the nanosecond level and polarization extinction ratio (PER) are considered for optimizing the performance of secure key rate (SIKR) quantitatively. For transmitting over 25 km optical fiber, the required PER should be above 22 dB when the pulse width is fixed to lns. Moreover, the optimal repetition frequency is obtained. In this case, 5.25 Mbps SKR can be achieved under the lns pulse width and 25dB PER, considering the $10^{11}$ finite-size block. Our work provides a systematic and theoretical framework for the study of improving the SKR of the dual-polarization CV-QKD system.

International Conference on Optical Communications and Networks (ICOCN)•Jul 31, 2023•2 citations
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 \ensuremathμs\ensuremath{\mu}\mathrm{s}\ensuremathμs. 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.
In a commercial fiber-based quantum key distribution system, the local and signal optical fields are transmitted through long distance fibers by using time division multiplexing and polarization multiplexing. The state of polarization of the optical field is inevitably disturbed by random birefringence of the standard single-mode fiber caused by external complex environments. This drift of the state of polarization significantly affects the balanced homodyne detection results and the secret key rate. Therefore, the key technology of the dynamic polarization control unit is crucial for the system in a large-scale commercial application. We theoretically analyze and prove that the polarization control unit only needs the combination of two degrees of freedom when considering the result of an arbitrary polarization extinction ratio at the receiver of the system. To overcome the influence of polarization variations, we propose a chaotic monkey algorithm based on Bayesian parameter estimation method and implement intelligence algorithm on field programmable gate array (FPGA) hardware under pulsed light with an integral-type detector for the dynamic polarization control unit. The simulation results show that the optimal combination is four degrees of freedom and the optimal prior distribution is an exponential distribution among various distributions in the dynamic polarization control unit. According to the simulation results, the experimental results show that the achieved polarization extinction ratio is over 30 dB and the average time of polarization control is 400 μs for a single random polarization scrambling. By combining the dynamic polarization control unit with the system, we demonstrate the continuous variable quantum key distribution (CV-QKD) under a continuous polarization scrambling scope of 0－2 krad/s and verify its effectiveness. In addition, the methods presented will improve the performance of the system and expand the range of applications even under strong external disturbance.
Continuous variable quantum key distribution (CV-QKD) can guarantee that two parties share secure keys even in the presence of an eavesdropper. However, the polarization direction of the coherent state transmitted in CV-QKD is susceptible to environmental disturbances during channel transmission, making it difficult to share keys consistently over long periods of time. Therefore, a CV-QKD system that can resist environmental disturbance is very urgent. In this paper, we propose a new optical architecture for CV-QKD based on the Faraday-Michelson interference (FMI) structure, and finally form an all-single-mode (SM) fiber-based stable CV-QKD system which employs transmitted local oscillator (TLO) scheme and discrete modulation coherent state (DMCS) protocol. Specifically, since the Faraday mirror rotates the polarization direction of light by 90 o , the birefringence effect of light can be effectively dealt with, thus ensuring the same polarization state of light before and after reflection. The final simulation results show that the theoretical secret key rate of this scheme can reach 139 kbps at 70 km, which can further improve the stability and robustness of CV-QKD in the real environment, and provide technical support for the next-generation high-stability QKD system.
Abstract The practical deployment of Continuous Variables Quantum Key Distribution (CV-QKD) systems benefits from existing optical fiber telecommunication infrastructures. However, optical fibers introduce random variations in the state of polarization, which degrades the system's performance.We consider a CV-QKD system featuring a polarization diversity heterodyne receiver and the constant modulus algorithm (CMA) to compensate for the polarization drifts in the quantum channel. Our setup can effectively realign Alice's quantum signal with Bob's local oscillator for polarization drift variances below 10−1010^{-10}10−10 .This value is compatible with most experimental implementations, allowing for accurate estimation of the channel transmission and excess noise parameters. This validates the approximation of real-world implementations under polarization drift to an ideal scenario without polarization drift, ensuring that the security proof remains applicable for polarization drift variances below $ 10^{-10} $.Our results establish operational limits for passive polarization drift compensation using a polarization diversity receiver combined with digital CMA.This enables long-term stability in \linebreak CV-QKD systems, eliminating the need for active polarization controllers and manual adjustments.
Continuous-variable quantum key distribution with a real local oscillator (LO) has been extensively studied recently due to its security and simplicity. Making it operate automatically and resistant to channel interference is the key to further long-term system operation. To overcome the dynamic changes in the state of polarization (SOP) of quantum signal caused by the random birefringence effect in fiber, Kalman filter is employed to estimate the polarization misalignment, thereby achieving polarization demultiplexing at the data level, and ultimately recovering the quantum signal with the help of a two-step phase compensation. The signal transmission and processing is simulated, which verifies the SOP tracking ability and the immunity to the fast phase drift. A proof-of-principle experiment is also conducted, and results show that it can resist the interference of SOP rotation at 1 krad/s, and has the ability to distribute 8.4 kbps secret key rate within 20 km when only considering SOP tracking imperfection, confirming its feasibility under harsh channel conditions.
The compensation process for the state of polarization (SOP) from quantum signal plays an important role in the practical implementation of continuous-variable quantum key distribution (CV-QKD). In contrast to the previous scheme using an expensive digital dynamic polarization controller, we choose a cheaper manual polarization controller interfaced with a digital algorithm based on Kalman filter to achieve compensation of the polarization loss under the condition that the SOP of the fiber is relatively stable. This paper also enumerates the details of other digital signal processing method to achieve final secret key rate. And a pilot-sequential Gaussian modulated coherent state (GMCS) continuous-variable quantum key distribution system with a local local oscillator (LLO) is experimentally implemented based on the analysis of excess noise. Finally, the experimental results show that the method of polarization loss compensation takes advantages in maintaining the stability of the final secret key rate. And a secret key rate of 110 kbps is achieved within 20 km optical fiber (with 4 dB loss) under the finite-size block of1×1061 \times {10^{6}}1×106during a more extended time in the laboratory.
In this article, we propose a time and orthogonal polarization division multiplexing scheme for local local oscillator continuous-variable quantum key distribution (LLO CV-QKD) system. According to the influence mechanism of time-domain diffusion and polarization disturbance on the key parameters, such as the channel transmittance and excess noise, of the studied system, we established a dual-polarization theoretical model and verified its validity by simulations. Here, the pulse width at the nanosecond level and polarization extinction ratio (PER) are considered for optimizing the performance of secure key rate (SIKR) quantitatively. For transmitting over 25 km optical fiber, the required PER should be above 22 dB when the pulse width is fixed to lns. Moreover, the optimal repetition frequency is obtained. In this case, 5.25 Mbps SKR can be achieved under the lns pulse width and 25dB PER, considering the 101110^{11}1011 finite-size block. Our work provides a systematic and theoretical framework for the study of improving the SKR of the dual-polarization CV-QKD system.