Performance research on mode-pairing quantum key distribution in satellite-to-ground quantum communication

This study investigates the performance of mode-pairing quantum key distribution (MP-QKD) over satellite-to-ground free-space channels. A nonuniform atmospheric transmission model is adopted to characterize key loss mechanisms, including turbulence, aerosol scattering, solar interference, and platform-induced beam jitter. Numerical simulations quantify the secret key rate under varying zenith angles and environmental conditions. Results show that increasing zenith angle significantly degrades the key rate because the longer optical path aggravates propagation loss and atmospheric impairment. Under identical atmospheric conditions, nighttime achieves a higher key rate than daytime, mainly because negligible solar interference leads to lower background-photon counts and a reduced QBER. Within the present simplified model, increasing the maximum pairing interval l improves the key rate, although the gain gradually saturates. These findings provide a performance evaluation of MP-QKD in a representative satellite-to-ground free-space configuration and offer practical guidance for parameter selection, environmental-sensitivity analysis, and robust system design.