Atmospheric effects on satellite-mediated continuous-variable quantum key distribution

Satellite-mediated quantum key distribution (QKD) has received considerable attention due to its potential to reach a global scale. Associated with this application is the atmospheric effects that set a notably restrict to the secret key rate. Here we demonstrate the atmospheric effects on satellite-mediated continuous-variable QKD with respect to the transmittance, fiber coupling, and excess noise. We consider the effects on both downlink and uplink while illustrating the discrepancy between them. Numerical analysis shows that downlink has more reliable transmittance than uplink while enduring a severe fiber coupling issue. It reveals that the discrepancy in transmittance is mainly due to the energy redistribution of the arriving beam. In addition, the time-of-arrival fluctuation notably reduces transmittance when the transmitted pulse half-width is sufficiently narrow (less than 10⁻¹³), and it introduces a controllable excess noise if the signal has a strong correlation with the local oscillator. (paper)