A novel synchronization scheme for free-space quantum key distribution system

We propose a novel synchronization scheme using a periodic light pulse for free-space quantum key distribution (QKD) system. For our 10MHz system, the repetition rate of timing pulse in the novel synchronization scheme can be reduced to 100 KHz or even lower. It allows employing a KHz repetition rate ultrashort pulse laser as timing synchronization source to implement high precision time synchronization. In this paper, short term time drift induced by atmospheric turbulence is analyzed, and how the time deviation impacts on the final secure key generation rate in our QKD system is calculated. In addition, we carried out the QKD experiments over the distance of 1.38 km. The results of the experiments indicate that our scheme is feasible.