Abstract

Continuous-variable quantum key distribution with a real local oscillator (LO) has been extensively studied recently due to its security and simplicity. Making it operate automatically and resistant to channel interference is the key to further long-term system operation. To overcome the dynamic changes in the state of polarization (SOP) of quantum signal caused by the random birefringence effect in fiber, Kalman filter is employed to estimate the polarization misalignment, thereby achieving polarization demultiplexing at the data level, and ultimately recovering the quantum signal with the help of a two-step phase compensation. The signal transmission and processing is simulated, which verifies the SOP tracking ability and the immunity to the fast phase drift. A proof-of-principle experiment is also conducted, and results show that it can resist the interference of SOP rotation at 1 krad/s, and has the ability to distribute 8.4 kbps secret key rate within 20 km when only considering SOP tracking imperfection, confirming its feasibility under harsh channel conditions.

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