Free-space discrete-variable quantum key distribution in mountainous environment

Abstract Free-space quantum key distribution (QKD) offers broader geographical coverage and more flexible system deployment compared to fiber-based systems. However, the free-space environment is highly complex, and various attenuation factors can significantly reduce key distribution efficiency or even lead to encoding failures. This paper discusses and analyzes the impact of turbulence and fog in mountainous environments on free-space discrete-variable quantum key distribution (DV-QKD). Through numerical simulation, the study examines the effects of altitude and visibility on transmittance and turbulence intensity, finding that turbulence intensity decreases with increasing altitude while transmittance increases; improvements in visibility also lead to increased transmittance. The beam wandering due to turbulence is also dominant, combining these factors, the effects on total transmittance and secret key rate are taken into consideration. Our main work would provide a certain reference for the deployment of practical QKD systems in actual mountainous environment.