The Impact of Rain–Fog Coexistence on Quantum Positioning
Xuchang Qu, Min Nie, Guang Yang
Abstract
To investigate the impact of rain-fog coexistence on quantum positioning performance, we analyzed-using raindropsize distribution functions and extinction coefficients-how visibility and propagation distance in such compound conditions affect photon energy, positioning error, quantum-channel fidelity, and bit-error rate. For a $\mathbf{1 0 ~ k m}$ link, the energy of a single photon drops to $1.87 \times 10^{-6} \mathrm{~J}$ when visibility is 0.7 km and to $1.59 \times 10^{-6} \mathrm{~J}$ when visibility falls to 0.6 km. While visibility decreases from 0.7 km to 0.5 km, and the photon energy is kept at $10 \times 10^{-5} \mathrm{~J}$, the positioning error grows from 0.826 cm to 1.017 cm. Although the exact decline differs slightly among channels, the fidelity of the quantum communication channel invariably decreases as visibility worsens. At a 1 km range, the channel bit-error rate rises to 0.24 when visibility is 0.50 km and to 0.14 when it is 0.55 km. These results demonstrate that rain-fog coexistence markedly degrades quantum positioning performance. Consequently, system parameters must be adjusted in real time according to the prevailing visibility and propagation distance to maintain the stability and reliability of quantum positioning systems operating in rain-fog environments.