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. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement