基于时分复用技术,采用一个单光子探测器(SPD)设计了基于BB84协议的 量子密钥分发(QKD)系统。 在接收端不同偏振态信号光的光路上依次增加6 m的延时光纤,使得不同偏振态信号光到达SPD的时间相应地依次相 差30 ns。在信号光与同步光精准同步的前提下,接收端对不同偏振态信号光的探测门进行编号, SPD在不同编号的 探测门处探测相应的偏振态光子。安全分析表明该QKD系统能够经受窃听者采取的截取-重发攻击,确保通信安全可 靠。该QKD系统成功应用于520 m的QKD实验,成码率为4.00 kbps, 误码率为1.5%。

Based on time-division multiplexing technology, a quantum key distribution (QKD) system based on BB84 protocol is designed by using a single photon detector (SPD). The delay fiber with an increase of 6 m in turn is added to the different polarization signal optical path at the receiving end, which makes the arrival time of different polarization signal light to the SPD vary by 30 ns in turn. On the premise of accurate synchronization of signal and synchronous light, the detecting gate of different polarization signal light is numbered at the receiving end. The corresponding polarized photons are detected by SPD at different numbering gates. Security analysis results show that the QKD system can resist intercept-resent attack by eavesdroppers and ensure the security and reliability of communications. The QKD system is successfully applied to the 520 m QKD experiment. The key rate is 4.00 kbps and bit error rate is 1.5%.