Unmanned aerial vehicles (UAVs) enable rapidly deployable secure communication, while quantum key distribution (QKD) ensures information-theoretic security over free-space optical channels. In UAV-assisted QKD, however, atmospheric turbulence and mobility-induced misalignment introduce stochastic channel fluctuations that cause intermittent secrecy degradation. Existing trajectory optimization methods are largely deterministic or risk-neutral and fail to address rare but severe deep-fading events. We develop a risk-sensitive stochastic control framework for robust UAV-assisted free-space QKD under atmospheric uncertainty. The UAV motion is modeled as a continuous-time stochastic dynamical system, and the quantum channel transmissivity is characterized by mobility-dependent log-normal fading, yielding a stochastic secret key rate process. The exponential performance functional simultaneously penalizes the propulsion energy and secrecy outage, resulting in a nonlinear risk-sensitive Hamilton-Jacobi-Bellman equation. Simulation results show that there is a significant reduction in secrecy outage probability and key rate variation when atmospheric turbulence exists, but there is only a relatively minor rise in the energy consumption for propulsion, achieving a robustness-efficiency tradeoff for secure aerial quantum communication.
Unmanned aerial vehicles (UAVs) enable rapidly deployable secure communication, while quantum key distribution (QKD) ensures information-theoretic security over free-space optical channels. In UAV-assisted QKD, however, atmospheric turbulence and mobility-induced misalignment introduce stochastic channel fluctuations that cause intermittent secrecy degradation. Existing trajectory optimization methods are largely deterministic or risk-neutral and fail to address rare but severe deep-fading events. We develop a risk-sensitive stochastic control framework for robust UAV-assisted free-space QKD under atmospheric uncertainty. The UAV motion is modeled as a continuous-time stochastic dynamical system, and the quantum channel transmissivity is characterized by mobility-dependent log-normal fading, yielding a stochastic secret key rate process. The exponential performance functional simultaneously penalizes the propulsion energy and secrecy outage, resulting in a nonlinear risk-sensitive Hamilton-Jacobi-Bellman equation. Simulation results show that there is a significant reduction in secrecy outage probability and key rate variation when atmospheric turbulence exists, but there is only a relatively minor rise in the energy consumption for propulsion, achieving a robustness-efficiency tradeoff for secure aerial quantum communication.
Quantum cryptography is a promising technology that achieves unconditional security, which is essential to a wide range of sensitive applications. In contrast to optical fiber, the free-space optical (FSO) link is efficiently used as a quantum channel without affecting the polarization of transmitted photons. However, the FSO link has several impairments, such as atmospheric turbulence and pointing errors, which affect the performance of the quantum channel. This paper proposes a quantum key distribution (QKD) scheme that uses a time-bin entanglement protocol over the FSO channel that suffers from various channel impairments. Due to the interest in unmanned aerial vehicles (UAVs) and their usefulness for many social, internet-of-things (IoT), civil, and military applications, the proposed QKD-FSO system is integrated with the ground-to-UAV platform. Furthermore, variances in the position and orientation of the UAV are investigated using a tracking system. These variances are considered when evaluating the overall performance of the proposed integrated system. For this purpose, closed-form expressions are obtained for the system average symbol error rate (ASER) and outage probability. The Monte Carlo simulation is used to verify the validity of the proposed expressions. The system security is investigated assuming photon number splitting (PNS) attack. Moreover, the transmit power, time-bin number, and modulation order are optimized to maximize the raw and secret key rates. The results show that for 500 m link, ASER22 mrad and signal-to-noise ratio > 7.5 dB which leads SNRth < 2.5 dB and raw key rate maximized by adjusting the number of time bins according to the received SNR.
This letter investigates a continuous-variable quantum key distribution (CV-QKD) protocol based on Gaussian-modulated coherent states over unmanned aerial vehicle (UAV)-based free-space optical (FSO) links. A realistic fading channel model is developed, including atmospheric turbulence, extinction, and UAV-induced pointing errors. We perform distance-dependent modulation variance optimization to maximize the secret key rate (SKR) under three scenarios: asymptotic, finite-block size (FBS), and FBS with adaptive optics (AO), based on numerical simulations incorporating a realistic UAV-FSO channel model. The results show that finite-size effects reduce the secure transmission range to ~800 m, while AO extends it to ~930 m. Furthermore, optimal modulation improves key rates by up to 40% compared to fixed modulation. This is the first work to jointly model UAV-FSO channel fluctuations, optimize modulation, and quantify finite-size security with AO, confirming the feasibility of CV-QKD for UAV-based communications.
We present a theoretical framework for quantum key distribution (QKD) using orbital angular momentum (OAM) encoded BB84 on an unmanned aerial vehicle (UAV) platform. A unified channel model captures Kolmogorov turbulence, pointing induced misalignment, and finite aperture clipping, enabling quantitative predictions of inter mode crosstalk and the resulting quantum bit error rate (QBER). Using a weak plus vacuum decoy state formulation, we derive composable finite key lower bounds on the secret key rate that incorporate statistical fluctuations, detector dark counts, efficiency mismatch, and error correction leakage. To stabilize performance under non stationary flight conditions, we introduce a lightweight physics informed learning module that combines physical priors with measured link statistics to classify valid pulses, reject corrupted data, and recommend decoding strategies. We outline a complete evaluation pipeline including UAV system architecture, turbulence driven QBER maps, decoy optimization, finite key scaling, and AI calibration metrics. Simulations indicate that under moderate turbulence and milliradian level pointing jitter, the proposed AI assisted method can improve the secret key rate by 10 percent to 30 percent while preserving composable security.
Unmanned aerial vehicles (UAV) based on free-space optical (FSO) systems combine the benefits of both the high data rate of the FSO and the mobility of UAV. However, cumulative effects of laser beam divergence and turbulence-induced fading on the received irradiance in the FSO link might allow an external eavesdropper located near the authorized receiver to break the transmission under certain conditions. Quantum key distribution (QKD) is a technique of secure communication that employs quantum mechanics-based cryptography principles. A combination of a continuous-variable quantum key distribution (CV-QKD) and Gaussian modulation of quantum coherent states (GMCS) enables a relatively secure communication system against collective attacks over FSO transmission links. However, the performance is restricted and degraded due to the influence of atmospheric turbulence and excess noise. This paper aims to evaluate the performance of a secured UAV-based FSO system utilizing prepare and measure CV-QKD protocol based on GMCS under collective attack in terms of quantum bit error rate (QBER), outage probability, and secret key rate (SKR) considering the impairments of the FSO channel, link budget, deviations in the position and attitude angles of the UAV, channel fluctuating transmittance, and excess noise. The system parameters, including transmit power, receiver’s field-of-view, and beam divergence angle, are optimized to satisfy the system’s design criteria of threshold-QBER=10−3and threshold outage probability=10−2. The proposed system tolerates boresight displacement up to 7 cm with the optimized values. The Closed-form expressions and analytical results are confirmed by Monte-Carlo simulations.
This paper develops a comprehensive analytical framework for modeling and performance evaluation of unmanned aerial vehicles (UAVs)-to-ground quantum communication links, incorporating key physical impairments such as beam divergence, pointing errors at both transmitter and receiver, atmospheric attenuation, turbulence-induced fading, narrow field-of-view (FoV) filtering, and background photon noise. To overcome the limitations of conventional wide-beam assumptions, we introduce a grid-based approximation for photon capture probability that remains accurate under tightly focused beams. Analytical expressions are derived for the quantum key generation rate and quantum bit error rate (QBER), enabling fast and reliable system-level evaluation. Our results reveal that secure quantum key distribution (QKD) over UAV-based free-space optical (FSO) links requires beam waists below 10 cm and sub-milliradian tracking precision to achieve Mbps-level key rates and QBER below 10−3. Additionally, we highlight the critical role of receiver FoV in balancing background noise rejection and misalignment tolerance, and propose adaptive FoV tuning strategies under varying illumination and alignment conditions. The proposed framework provides a tractable and accurate tool for the design, optimization, and deployment of next-generation airborne quantum communication systems.
Free-space quantum key distribution (QKD) allows two distant parties to share secret keys with information-theoretic security, which can pave the way for satellite-ground quantum communication to set up a global network for sharing secret message. However, free-space channels in the presence of atmospheric turbulence are affected by losses and fluctuating transmissivity which further affect the quantum bit error rate and the secure key rate. To implement free-space QKD, it is indispensable to study the effect of atmospheric turbulence. Different models have been used to describe the probability distribution for channel transmission coefficient under atmospheric turbulence, including the log-normal distribution and K distribution. In this paper, we focus on free space measurement-device-independent quantum key distribution (MDI-QKD) under K-distributed strong atmospheric turbulence. The MDI-QKD can close all loopholes on detection and achieve a similar performance to QKD, relying on time-reversed version of entanglement-based QKD protocol. Threshold post-selection method is adopted to restrain detrimental effects of the atmospheric turbulence, which is based on the selection of the intervals with higher channel transmissivity. By combining the general MDI-QKD system model with this method, we present a framework for the optimal choice of threshold. Our simulation result shows that the optimal threshold is dependent on the turbulence intensity and expected channel loss. Furthermore, compared with the original MDI-QKD protocols, the proposed protocol with threshold post-selection method can acquire a considerable better performance in key rate, especially in regions of high turbulence and high loss. What is more, this is instructive to the building of a practical free-space MDI-QKD system with better performance.