Pulsed light high-speed polarization locking method of continuous-variable quantum key distribution system

A pulsed light high-speed polarization locking method of a continuous-variable quantum key distribution (CV-QKD) system, the method comprising:

• modulating a continuous light source to generate a pulsed light;
• splitting the pulsed light into a local oscillator and a signal light through a transmitter beam splitter;
• transmitting the local oscillator and the signal light in a same fiber by time division multiplexing and polarization multiplexing at a transmitting end of a CV-QKD system, and
• transmitting the local oscillator and the signal light through a long-distance single-mode fiber to reach a receiving end;
• recovering a synchronous clock signal of the CV-QKD system at the receiving end by splitting a portion of the transmitted light utilizing a receiver beam splitter;
• conducting polarization demultiplexing of the local oscillator and the signal light on a remaining portion of the light through a dynamic polarization controller and a polarization beam splitter, and splitting the local oscillator by utilizing the receiver beam splitter to obtain a portion of the local oscillator as a first feedback signal of high-speed polarization locking;
• detecting and converting the first feedback signal into a peak voltage of an output electric pulse through an optical signal detector, and by utilizing a system synchronous clock as a trigger signal, monitoring intensity changes of pulsed light in real time by acquiring the peak voltage of the output electric pulse;
• and
• simultaneously utilizing the acquired peak voltage as a second feedback signal to conduct a conditional simulated annealing algorithm to search a target polarization state, to obtain a polarization locking signal, and load the polarization locking signal to the dynamic polarization controller so as to achieve high-speed polarization locking of pulsed light.