Phase compensation based on step-length control in continuous-variable quantum key distribution.

Phase compensation is a dispensable procedure to reduce the difference between legitimate parties in continuous-variable quantum key distribution (CVQKD) because of the unavoidable phase drift of the quantum signals. However, it is a difficult task to compensate the fast drifted phase accurately. Here, we propose a novel phase compensation scheme based on an optimal iteration algorithm. Analysis shows that this scheme can make the phase compensation reach a higher precision level while simultaneously ensuring the efficiency. When the accuracy is determined, we can minimize the number of iterations by controlling the step-length to increase the algorithm efficiency. Moreover, we can improve the accuracy of phase compensation by means of changing the step-length. This work breaks the bottleneck of accuracy problem in phase compensation and contributes to the performance of the whole CVQKD system.