Abstract Driven by the necessitates of wide-area quantum secure communication networks, ground-to-satellite quantum key distribution (QKD) has been highlighted in the field of quantum information. Continuous variable QKD (CV-QKD) shows the advantages of a high secure key rate generation and compatibility in the fiber channel, but the communication range is limited by low attenuation tolerance. In this study, the feasibility of the uplink CV-QKD for Very Low Earth Orbit satellite is studied, and the influence of practical factors such as atmospheric turbulence and beam pointing errors under dynamic time-varying satellite orbital parameters is analyzed to model realistic transmission channels. A parameter optimization scheme for orbital parameters, spot size, receiving telescope aperture, and modulation variance has been proposed to enhance the performance of the actual uplink CV-QKD, providing a reference for parameter selection in CV-QKD experiments.
Abstract Driven by the necessitates of wide-area quantum secure communication networks, ground-to-satellite quantum key distribution (QKD) has been highlighted in the field of quantum information. Continuous variable QKD (CV-QKD) shows the advantages of a high secure key rate generation and compatibility in the fiber channel, but the communication range is limited by low attenuation tolerance. In this study, the feasibility of the uplink CV-QKD for Very Low Earth Orbit satellite is studied, and the influence of practical factors such as atmospheric turbulence and beam pointing errors under dynamic time-varying satellite orbital parameters is analyzed to model realistic transmission channels. A parameter optimization scheme for orbital parameters, spot size, receiving telescope aperture, and modulation variance has been proposed to enhance the performance of the actual uplink CV-QKD, providing a reference for parameter selection in CV-QKD experiments.
Continuous variable quantum key distribution (CV-QKD) has emerged as a promising candidate for quantum-secure communication due to its experimentally demonstrated high key rates in fiber-optic channels. However, the feasibility of discrete modulation CV-QKD in satellite-to-ground downlinks remains an open question due to practical challenges such as high transmission loss, limited communication windows, and atmospheric turbulence. In this work, a comprehensive framework is proposed to evaluate the feasibility of discrete modulation CV-QKD by integrating orbital dynamics and atmospheric channel models, and to comprehensively analyze the influence of the parameter space on free-space discrete modulation CV-QKD. To achieve this, a free-space CV-QKD simulation platform is employed, which calculates the elevation angle and transmission distance based on precise orbital models, thereby providing a more practical assessment of the key rate for discrete modulation CV-QKD. Simulation results verify the feasibility and practicality of discrete modulation CV-QKD in satellite-based quantum communication systems. Furthermore, the critical factors influencing the key rate performance are identified, and parameter optimization strategies are proposed, providing theoretical support for realizing the future satellite-to-ground discrete modulation CV-QKD.
Satellite-based quantum key distribution (QKD) has lately received considerable attention due to its potential to establish a secure global network. Associated with its application is a turbulent atmosphere that sets a notable restriction to the transmission efficiency, which is especially challenging for ground-to-satellite uplink scenarios. Here, we propose a novel noiseless attenuation (NA) scheme involving a zero-photon catalysis operation for source preparation to improve the performance of continuous-variable (CV) QKD over uplink. Numerical analysis shows that the NA-based CV-QKD, under attenuation optimization, outperforms the traditional CV-QKD, which is embodied in extending the allowable zenith angle while improving the effective communication time. Attributing to characteristics of the attenuation optimization, we find that the NA-involved source preparation improves the security bound by relatively reducing the amount of information available to eavesdroppers. Taking the finite-size effect into account, we achieve a tighter bond of security, which is more practical compared with the asymptotic limit.
Abstract For a practical continuous-variable quantum key distribution (CV-QKD) system, the optimization of modulation variance is crucial for promoting protocol performance. The optimization relies on algorithms like local search in general. But the efficiency of local search methods is limited in low latency and limited computing power scenarios due to their high computational consumption. Hence, this optimization approach is infeasible for satellite-based CV-QKD due to satellites’ low power feature. In this paper, a neural network model that directly predicting the optimal modulation variance in nearly real time is proposed for free space gaussian modulated CV-QKD protocols. This work enhances the feasibility of implementing CV-QKD in low-Earth-orbit satellite scenarios, where typical link durations of few seconds demand rapid parameter optimization. Moreover, a simulation platform for free space CV-QKD protocol, which employs the precise orbital model to extract the elevation angle and the transmission length, is designed and developed to generate training sets that make the neural network model more practical. Our work can be used as a foundation to support parameter prediction for future quantum communication satellite missions.
This paper deals with a channel-parameter estimation for continuous-variable quantum key distribution (CV-QKD) over a satellite-to-submarine link. In particular, we focus on the channel transmittances and the excess noise which are affected by atmospheric turbulence, surface roughness, zenith angle of the satellite, wind speed, submarine depth, etc. The estimation method is based on proposed algorithms and is applied to low-Earth orbits using the Monte Carlo approach. For light at 550 nm with a repetition frequency of 1 MHz, the effects of the estimated parameters on the performance of the CV-QKD system are assessed by a simulation by comparing the secret key bit rate in the daytime and at night. Our results show the feasibility of satellite-to-submarine CV-QKD, providing an unconditionally secure approach to achieve global networks for underwater communications.
Satellite-based Quantum Key Distribution (QKD) is emerging as a cornerstone technology for secure global communication networks, extending quantum-safe key exchange beyond the limitations of terrestrial fiber systems. Achieving scalable and robust space-to-ground QKD links requires careful optimization of optical terminals, channel conditions, and protocol-specific parameters.In this work, we present a system-level analysis of design priorities for satellite QKD networks, using realistic atmospheric conditions modeled with MODTRAN 6 and a simulation tool designed and developed in-house. For discrete-variable (DV) QKD, we analyze how the secret key rate (SKR) varies with satellite altitude for two telescope aperture sizes under representative rural and urban ground station scenarios. Results show that DV-QKD enables secure key distribution over distances compatible with LEO and MEO satellite links when using moderately sized ground telescopes (600mm and 800mm apertures). For continuous-variable (CV) QKD with Gaussian modulation, SKR is analyzed as a function of satellite altitude under the most favorable link conditions identified in the DV-QKD study (800 mm ground aperture and rural environment), indicating that CV-QKD is feasible for secure key exchange with low-altitude LEO satellites, as long as the excess noise remains within low (yet experimentally achievable) levels (≈ 0.045 SNR). Additionally, we establish upper bounds on tolerable excess noise via heatmap analysis, defining the operational regime for secure CV-QKD.These findings provide quantitative guidance for designing scalable, interoperable, and cost-efficient space-to-ground QKD infrastructures, supporting the development of robust global quantum communication networks.
This paper develops a hybrid quantum channel model tailored for finite-regime quantum key distribution (QKD) in free-space satellite quantum communication. The channel model addresses the fading characteristics of satellite-to-ground links while incorporating the dynamics of satellite orbits. By conducting a comprehensive security analysis under finite-size effects and collective attacks, the research bridges the theoretical and practical aspects of satellite-based QKD. Critical parameters, such as reconciliation efficiency, transmission coefficient, detection efficiency, receiver telescope aperture, beam waist, and effective communication time, are systematically investigated to optimize the secret key rate. The study reveals key trade-offs between the influence of satellite altitude on communication windows, noise levels, and synchronization, which significantly impact quantum channel efficiency. The model improves the accuracy of free-space quantum channel evaluations by presenting a hybrid noise framework that combines quantum Poissonian noise with classical additive white Gaussian noise (AWGN). Our numerical results demonstrate the feasibility and robustness of finite-regime QKD for uplink and downlink configurations in various atmospheric conditions, highlighting the superiority of satellite-based quantum communication over conventional networks.