Experimental Demonstration of LLO Continuous-Variable Quantum Key Distribution With Polarization Loss Compensation

compensation process for the state of polarization (SOP) from quantum signal plays an important role in the practical implementation of continuous-variable quantum key distribution (CV-QKD). In contrast to the previous scheme using an expensive digital dynamic polarization controller, we choose a cheaper manual polarization controller interfaced with a digital algorithm based on Kalman filter to achieve compensation of the polarization loss under the condition that the SOP of the fiber is relatively stable. This paper also enumerates the details of other digital signal processing method to achieve final secret key rate. And a pilot-sequential Gaussian modulated coherent state (GMCS) continuous-variable quantum key distribution system with a local local oscillator (LLO) is experimentally implemented based on the analysis of excess noise. Finally, the experimental results show that the method of polarization loss compensation takes advantages in maintaining the stability of the final secret key rate. And a secret key rate of 110 kbps is achieved within 20 km optical fiber (with 4 dB loss) under the finite-size block of 1 x 10(6) during a more extended time in the laboratory.

Automated summary

The compensation process for the state of polarization (SOP) from quantum signal is crucial for practical implementation of CV-QKD. Instead of using an expensive digital dynamic polarization controller, this study utilizes a cheaper manual polarization controller and a digital algorithm based on Kalman filter to achieve polarization loss compensation when the SOP of the fiber is relatively stable. Other digital signal processing methods are also discussed for final secret key rate. Experimental results show that this polarization loss compensation method maintains the stability of the final secret key rate and achieves a secret key rate of 110 kbps within 20 km optical fiber (with 4 dB loss) under finite-size block of 1 x 10(6) over an extended time in the laboratory.