Research On Phase Compensation Algorithm For Continuous Variable Quantum Key Distribution

With the development of information technology,the problem of information security has become increasingly prominent,which has become the focus of the whole society.Compared with the traditional cryptosystems,the security of quantum key distribution is guaranteed by the no-cloning theorem and the uncertainty principle,which enables both parties to share a set of theoretically unconditional security keys.From the perspective of future development trends and social needs,quantum key distribution has broad application prospects.Quantum key distribution is mainly divided into two categories:discrete variable protocol and continuous variable protocol.continuous variable protocol based on the Gaussian modulation coherent state has the advantages of low cost,strong compatibility,and high stability,which has attracted a large number of scholars to conduct research.In the practical continuous variable quantum key distribution system,the phase noise will shorten the transmission distance and reduce the security key rate,so phase compensation is very important to improve the performance of the system.Different from the algorithm based on potential difference and covariance,kalman filter can reduce the influence of noise and further improve the accuracy of phase estimation.Aiming at the problem of phase drift,this paper designs a real-time phase compensation scheme based on Kalman filter.The specific content are as follows:1)Complete the modeling of the quantum key distribution system based on the Gaussian modulation coherent state,design the calculation architecture of the kalman filter based on FPGA,which is mainly divided into state prediction,gain calculation and prediction correction modules.The module is implemented on the Kintex-7 series development board.2)Test the phase noise,mainly analyze the phase noise characteristics of the system and verify the effectiveness of the frame structure.The experimental results show that the mean value and variance of the phase noise are 1.59 and 10378.53,and the phase drift rate is about 364.150/s(6.36rad/s).3)Test the accuracy of the phase compensation algorithm.In the scheme without changing the signal-to-noise ratio of the reference frame,when the channel attenuation is 13dB,the mean and variance of the residual phase noise are 0.86 and 138.03.After amplifying the reference frame,the residual phase under the same conditions he mean and variance of the residual phase noise are 0.37 and 49.68.When the channel attenuation is 20dB,the mean and variance of the residual phase noise are-0.81 and 275.71.