Satellite FSO/QKD systems employ free-space optical links between satellites and ground stations to achieve long-distance quantum key distribution. However, these systems face challenges from atmospheric turbulence. This paper introduces a theoretical framework to evaluate the influence of phase fluctuations caused by atmospheric turbulence on the system performance. Mathematical expressions for key performance metrics are derived and validated through Monte- Carlo simulations. Using results from the framework, we provide a recommended system setup to fulfil the QKD performance requirements under different atmospheric turbulence conditions.
Satellite FSO/QKD systems employ free-space optical links between satellites and ground stations to achieve long-distance quantum key distribution. However, these systems face challenges from atmospheric turbulence. This paper introduces a theoretical framework to evaluate the influence of phase fluctuations caused by atmospheric turbulence on the system performance. Mathematical expressions for key performance metrics are derived and validated through Monte- Carlo simulations. Using results from the framework, we provide a recommended system setup to fulfil the QKD performance requirements under different atmospheric turbulence conditions.
Abstract Quantum Key Distribution (QKD) provides information-theoretic security for future communication networks by exploiting the fundamental principles of quantum mechanics. However, satellite-to-ground QKD links suffer significant performance degradation due to atmospheric turbulence, absorption, scattering, and satellite-induced pointing errors. This paper investigates the BB84 QKD protocol over a Free-Space Optical (FSO) channel modeled using the Gamma–Gamma distribution, which accurately captures both small-scale and large-scale atmospheric irradiance fluctuations. Closed-form and numerical results for outage probability and Quantum Bit Error Rate (QBER) are presented under weak, moderate, and strong turbulence regimes. The Secure Key Rate (SKR) is analyzed as a function of link distance under clear and foggy weather conditions. Additionally, the impact of satellite vibration is evaluated using a jitter-dependent pointing error model, demonstrating that misalignment significantly reduces link reliability. Simulation results show that strong turbulence conditions introduce more than 15 dB SNR penalty compared to clear-sky operation, while haze conditions limit QKD range to under 8–10 km. These findings provide practical performance benchmarks for Low-Earth Orbit (LEO) quantum downlinks in realistic atmospheric environments. The results provide practical insights for electronic receiver design and system implementation of satellite quantum communication links.
Atmospheric turbulence is the major challenge to satellite-to-ground quantum key distribution (QKD), yet most performance models treat turbulence only through average statistics, masking temporal loss fluctuations that dominate real links. Here we present an end-to-end, time-evolving satellite-to-ground QKD model that embeds a phase-screen description of turbulence into beam propagation, focusing, tracking, adaptive-optics compensation, and single-mode fiber (SMF) coupling. The simulation delivers the instantaneous channel loss L channel ( t ) and thermal photon dark counts D C bgn , from which we estimate the finite-size secret key rate (SKR) and evaluate the performance of turbulence mitigation techniques. For a GEO-to-Lijiang Station link, the optimized configuration enables day-and-night QKD operation under favorable weather conditions, although the daytime link margin remains limited. This study complements conventional time-averaged models by offering a more realistic and detailed framework for analyzing satellite-to-ground QKD performance and the effectiveness of mitigation techniques under time-evolving turbulence.
Abstract In this paper, we analyze the performance of free-space optical quantum key distribution (FSO-QKD) using the BB84 protocol with BPSK modulation under realistic channel conditions. The Málaga distribution is employed to model the composite atmospheric turbulence, considering pointing errors. We derive closed-form expressions for the average quantum bit error rate (QBER) and the secure key rate (SKR), incorporating both turbulence and misalignment effects. Numerical results demonstrate the impact of turbulence parameters and beam misalignment on system performance. The findings provide insights for the robust design of FSO-QKD systems under practical deployment conditions.
We investigate the performance of relativistic quantum key distribution (RQKD) over turbulent free-space optical channels for both single-photon and coherent-state implementations. A theoretical model is developed to describe the effect of atmospheric turbulence on interferometric visibility and secret-key generation by incorporating turbulence-induced phase fluctuations into the key-rate analysis. Numerical simulations are performed under realistic channel conditions to evaluate the achievable communication distance and secret-key rate. The results show that atmospheric turbulence degrades the protocol performance by reducing interference visibility, with the severity of the degradation determined by the ratio between the interferometer-arm separation r (or temporal separation of signal and reference states ΔT) and Fried's parameter. The single-photon protocol remains operational over all investigated turbulence regimes, whereas the coherent-state implementation exhibits a critical dependence on the interferometer geometry (especially on ΔT), leading to a threshold beyond which secure key generation is no longer possible. These findings quantify the impact of atmospheric turbulence on relativistic quantum key distribution and provide practical guidelines for the design and optimization of free-space RQKD systems.
Atmospheric conditions play a pivotal role in determining the performance of satellite-to-ground quantum key distribution (QKD). In this research, we meticulously investigate the influence of various factors, including background light, dark counts, and aperture coupling efficiency, on the performance of satellite-to-ground QKD under different levels of turbulence intensity associated with diverse atmospheric stratifications. Based on the decoy state BB84 protocol, we refine the calculation formula for the quantum bit error rate (QBER) of the satellite-to-ground QKD system. Subsequently, we conduct simulations to analyze how the quantum BER varies under different conditions, such as varying intensities of background light, different wavelengths, and different zenith angles. The simulation results reveal that, when taking all the above-mentioned factors into comprehensive consideration, employing signals with shorter wavelengths can lead to a more favorable QBER. The findings of this study offer valuable insights and a solid reference for the construction of a satellite-to-ground QKD system, facilitating the development of more reliable and efficient quantum communication links between space and the ground.
As a practical version of twin-field quantum key distribution (TF-QKD), phase-matching quantum key distribution (PM-QKD) is able to surpass the linear bound without quantum repeaters. Implementing PM-QKD through free space can guarantee two parties to share unconditionally secure keys between ground stations and mobile platforms. However, atmospheric turbulence decreases the free-space secure key rate as the result of fluctuations of transmittances caused by it. This paper includes two works we do. First, for generality, we derive the secure key rate formula of 4-intensity PM-QKD based on asymmetric channel transmittances. Second, we numerically simulate the performance of PM-QKD in free space and ideal circumstance to study the effect of the atmospheric turbulence.