A Hybrid Noise Approach to Modeling of Free-Space Satellite Quantum Communication Channel for Continuous-Variable QKD

This research advances the application of Quantum Key Distribution (QKD) in Free-Space Optics (FSO) satellite-based quantum communication. It proposes an innovative satellite quantum channel model and derives the secret quantum key distribution rate achievable through this channel. Unlike existing models that approximate the noise in quantum channels as merely Gaussian distributed, this model incorporates a hybrid quantum noise analysis, accounting for both quantum Poissonian noise and classical Additive-White-Gaussian Noise (AWGN). This hybrid approach acknowledges the dual vulnerability of continuous variables (CV) Gaussian quantum channels to both quantum and classical noise under collective attack with reverse-reconciliation (RR) setting, thereby offering a more realistic assessment of the quantum Secret Key Rate (SKR). This work delves into the variation of asymptotic SKR with the Signal-to-Noise Ratio (SNR) and satellite altitudes under various influencing parameters. We identify and analyze critical factors such as reconciliation efficiency, electrical noise, transmission coefficient, detection efficiency, transmission efficiency, excess noise, and the quantum Poissonian noise parameter impacting the SKR. These parameters are pivotal in determining the asymptotic SKR in FSO satellite quantum channels, highlighting the challenges of satellite-based quantum communication. A comparative study has been provided based on the finite-size and asymptotic SKR. It provides a comprehensive framework for understanding and optimizing asymptotic SKR in satellite-based QKD systems, paving the way for more efficient and secure quantum communication networks.