Spatially Adaptive Detection for Satellite-based QKD under Atmospheric Turbulence Channel

2026-05-15

AI Summary

Atmospheric turbulence distorts the received optical beam in satellite-based quantum key distribution (QKD), rendering single-point detection highly susceptible to background noise and degrading system performance. This work introduces spatially adaptive detection to satellite QKD for the first time, leveraging the spatial degrees of freedom offered by a single-photon detector array. A threshold-driven dynamic selection mechanism is proposed to activate, in real time, only those detector elements with the highest probability of receiving valid quantum signals. Through Monte Carlo simulations that model beam propagation, atmospheric turbulence effects, and various noise sources, the proposed approach significantly reduces the quantum bit error rate (QBER) and enhances the secure key rate (SKR), thereby improving the robustness of satellite QKD systems operating over realistic atmospheric channels.

Abstract

Quantum key distribution (QKD) provides information-theoretic security and satellite-based quantum key distribution (SatQKD) has demonstrated the potential to extend this communication security to intercontinental scales. However, atmospheric turbulence induces significant distortion in the spatial distribution of received optical beams, while background noise remains approximately uniform across the detector plane. As a result, single-element qubit (quantum bit) detection can be frequently dominated by noise due to the random spatial pattern of the imaged wavefront, thereby degrading the system performance. To address this limitation, we propose to exploit the spatial degrees of freedom of single-photon detector arrays to reject the excessive noise while adapting to channel variations induced by turbulence. We develop a threshold-based selection method that only activates detector elements that have higher probability of registering qubits. We evaluate the performance of the proposed noise-rejection QKD schemes using Monte Carlo simulations considering the impact of diffraction and atmospheric turbulence on the transmitted optical beam in the presence of background and dark noise. The results show that, compared to conventional schemes, the proposed noise-rejection strategy effectively reduces the quantum bit error rate (QBER) and improves the secret key rate (SKR) performance, while the performance gains depend on the turbulence condition. These findings demonstrate the potential of adaptive array receiver design to enhance the robustness of the SatQKD system under realistic atmospheric conditions.

Problem

• satellite-based QKD
• atmospheric turbulence
• spatial distortion
• background noise
• quantum bit error rate

Innovation

• spatially adaptive detection
• satellite-based QKD
• single-photon detector array
• atmospheric turbulence
• quantum bit error rate