Performance analysis of the satellite-to-ground continuous-variable quantum key distribution with orthogonal frequency division multiplexed modulation

Abstract

Continuous-variable quantum key distribution (CVQKD) is aiming at widespread application and adoption in different scenarios, and thus, the application of satellite-to-ground link may play a vital role in establishing the global secure quantum communications. In this paper, we propose an improved tunable CVQKD scheme for the satellite-to-ground free space optical (FSO) link in an orthogonal frequency division multiplexing (OFDM) system. The OFDM-based CVQKD can effectively suppress the random fading effect that resulted from the atmospheric channel since it divides the initial transmission channel into multi-subcarriers working in parallel so as to compensate the weakness of single-channel transmission of the signals. Moreover, the influence of the intensity scintillation, atmospheric transmittance and phase noise caused by atmospheric turbulence is involved in security analysis. The results reveal that satellite-to-ground CVQKD system can reduce the atmosphere influence in an OFDM system. Compared with the single-channel CVQKD in the FSO link, the secret key rate is improved with the OFDM technique within a certain range of subcarrier numbers. Nevertheless, the reduction of symbols per channel cannot make the asymptotic assumption due to the limitation of technology and devices.