Stable quantum key distribution with active polarization control based on time-division multiplexing

Polarization-encoding provides a promising approach for the practical quantum key distribution (QKD) system due to the simple encoding and decoding method. Here we present a long-term stable polarization-encoding QKD with a real-time polarization control. The polarization of the signal photons in the optical fiber was maintained stable by using time-division-multiplexed reference pulses for feedback control. We implemented this technique in the QKD experiment in 50 km fiber to show that it could facilitate polarizationencoded quantum communication. The system operated stably for ∼460 min, and the quantum bit error rate was ∼5.27%. The raw key generating rate in this system was kept stable at ∼500 bits s-1. The advantages and disadvantages of the previous polarization-control schemes were also rigorously analyzed.