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.
We presented an advanced design of receiver in free space quantum key distribution (QKD) system based on BB84
protocol. In this system, a novel four polarization beam splitter is used in the receiver. It simplifies the receiver
fabrication process, and the reflection loss is reduced too. Then we built the transmitter and the receiver for QKD system.
The outdoor 200m free space QKD experiment was carried out, the bit error rate is 0.91% when the average photon
number in each optical pulse was about 0.1. This result indicates that our design for the QKD system is feasible.