Polarization compensation method based on the wave plate group in phase mismatch for free-space quantum key distribution
Key Laboratory of Space Active Optoelectronic Technology, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 200083, Shanghai, China
2 University of Chinese Academy of Sciences, 100049, Beijing, China
3 Shanghai Quantum Science Research Center, 201315, Shanghai, China
Accepted: 8 February 2023
Published online: 13 February 2023
Maintaining the polarization state in communication terminals is vital for polarization-encoding free-space quantum key distribution (QKD). Wave plate group phase mismatch caused by manufacturing errors, complex environmental effects, and the working wavelength deviation can reduce the polarization compensation effect. We found in theoretical analysis, that increasing phase mismatch of wave plates leads to the compensation method failure and reduces robustness. We propose a complementary polarization compensation method, which can effectively improve the robustness. Experimental results show that this method can improve the compensation effect by 50% at a slight phase mismatch, and realize a polarization extinction ratio exceeding 250:1 at the ergodic area even if the phase deviates to 0.27π. This method is beneficial to the high-stability design of free-space QKD systems and has the potential to be applied to QKD systems operating at multiple wavelengths.
Key words: Quantum key distribution / Free-space / Polarization compensation / Wave plate group / Phase mismatch
© The Author(s) 2023
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