Free-space optical (FSO) quantum communication offers strong potential for secure, high capacity data transmission, but remains vulnerable to covert physical-layer attacks. This paper presents a rigorous analysis of vacuum state jamming—an adversarial strategy where the jammer probabilistically replaces transmitted pulses with vacuum states, thereby reducing effective photon counts without adding excess noise. We consider a binary phase-shift keying coherent-state quantum system over a Gamma–Gamma atmospheric turbulence channel. A consistent mixture model is developed for the jammed states, and optimal Helstrom detection is applied to derive exact expressions for the quantum bit error rate (QBER) under turbulence and jamming. For secure information throughput, the Holevo capacity is evaluated numerically from density operator eigenvalues. Numerical results confirm that vacuum jamming induces measurable degradation of both QBER and Holevo capacity, with stronger effects under high turbulence and lower signal energies. Comparisons between exact integral results and common approximations highlight the latter’s limited validity range. The framework not only quantifies the resilience of quantum FSO links against vacuum jamming, but also provides a foundation for developing jamming-aware monitoring and countermeasures.
Free-space optical (FSO) quantum communication offers strong potential for secure, high capacity data transmission, but remains vulnerable to covert physical-layer attacks. This paper presents a rigorous analysis of vacuum state jamming—an adversarial strategy where the jammer probabilistically replaces transmitted pulses with vacuum states, thereby reducing effective photon counts without adding excess noise. We consider a binary phase-shift keying coherent-state quantum system over a Gamma–Gamma atmospheric turbulence channel. A consistent mixture model is developed for the jammed states, and optimal Helstrom detection is applied to derive exact expressions for the quantum bit error rate (QBER) under turbulence and jamming. For secure information throughput, the Holevo capacity is evaluated numerically from density operator eigenvalues. Numerical results confirm that vacuum jamming induces measurable degradation of both QBER and Holevo capacity, with stronger effects under high turbulence and lower signal energies. Comparisons between exact integral results and common approximations highlight the latter’s limited validity range. The framework not only quantifies the resilience of quantum FSO links against vacuum jamming, but also provides a foundation for developing jamming-aware monitoring and countermeasures.
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 investigates the performance of coherent-state quantum optical wireless communication systems operating over atmospheric turbulence channels with pointing errors (PEs). The average error probability (AEP) and average achievable rate (AAR) are analyzed for on–off keying (OOK) and binary phase-shift keying (BPSK) signaling under photon-counting (PC), homodyne, and optimal Helstrom detection. The proposed framework jointly incorporates deterministic path loss, atmospheric turbulence, and PEs, and accommodates multiple statistical channel models, including Gamma-Gamma (GG), doubly inverted Gamma-Gamma (IGGG), and Fisher-Snedecor F distributions, within a unified analytical formulation. Closed-form expressions for AEP and AAR are derived via direct probability density function (PDF)-based integration of the conditional error probability, along with high-photon-number asymptotic approximations that provide insight into performance scaling behavior. Numerical results validate the analytical expressions and demonstrate the impact of PEs on system performance. The analysis further enables systematic comparison between classical and optimal quantum detection schemes and quantifies the achievable performance gains under different channel conditions. These results provide useful design insights for modulation and receiver selection in turbulent free-space optical (FSO) communication systems.
In this letter, we analyze the average probability of error of quantum modulation schemes in weakly turbulent quantum communication channels utilizing coherent states. Atmospheric turbulence-induced fading is a significant challenge that degrades the performance of free-space quantum communication systems. We derive and present closed-form expressions for the average probability of error for various detection methods: classical (shot-noise limited) single-photon detection, coherent detection, and the optimal quantum hypothesis-testing (Helstrom) detection for binary quantum modulation schemes. Our analysis focuses on the transmission of classical data modulated by quantum coherent states over a log-normal turbulent channel. Additionally, we discuss the lower bounds of the average capacities for Helstrom detection, providing comprehensive insights into the achievable information rates in realistic atmospheric conditions. The derived expressions show excellent agreement with numerical Monte Carlo simulations across a broad range of average transmitted photon numbers, offering valuable guidelines for the design and optimization of quantum communication systems.
This work is concerned with the physical layer security of the free space optical (FSO) communication network comprising of a transmitter, a receiver, an eavesdropper (Eve), and a friendly reactive jammer that aims to thwart the activity of the Eve. As the key feature of this work, we calculate the discrete-input-continuous-output for memory-less channel (DCMC) capacity of the authentic and eavesdropping channel in the presence of the atmospheric turbulence characterised by$\alpha -\mu $probability density function (PDF), zero and non-zero boresight pointing error, and partial band or broadband jamming noise. For this purpose, novel PDFs for all-encompassing conditions of FSO channel and the received signals at different nodes of the considered system are formulated. Thereafter, we devise schemes to wane the effect of a vicious Eve by formulating novel closed-form expressions of average secrecy capacity for both strategies. Our derived analytical expressions can be used as tools to examine the DCMC capacity and secrecy capacity for different turbulence regimes of FSO link, severity of boresight errors, and activity of a friendly jammer. The mathematical results are affirmed by Monte-Carlo simulation. We exhibit that deploying a friendly jammer to assist enhancing the security of an FSO system is very conducive as it makes the Eve to hike its signal-to-jamming-noise ratio by almost 10 dB when the jammer’s activity increases from 10% to 100% of the time frame of data transmission.
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.
Abstract This investigation examines the use of a Quadrature Phase Shift Keying (QPSK)-based Free-space Optical (FSO) Communication system combined with Quantum Key Distribution (QKD) for improved security and dependability in disaster management situations. We tackle the problems caused by atmospheric turbulence by utilizing a hybrid gamma–gamma and log–normal channel model to precisely characterize the FSO link. The proposed system’s purpose is to offer secure, high-bandwidth communication for emergency response coordination, telemedicine, and data transmission in environments affected by disasters. We present a system design and performance evaluation based on the hybrid atmospheric model, discuss the potential advantages, drawbacks, and countermeasures of the approach, and propose future research avenues, encompassing real-time adjustment, modulation variability, and field testing. Our implementation of real-time adaptation mechanisms lowers the BER by about 30 % under conditions affected by turbulence, while hybrid FSO/RF switching maintains uninterrupted connectivity during severe atmospheric attenuation.