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IEEE Journal of Quantum Electronics

Pointing Error Influence on Quantum Key Distribution

Yalçın Ata, Kamran Kıasaleh

Published Oct 31, 2025• 3 citations
Publisher

Abstract

Recently, quantum key distribution (QKD) has emerged as a prominent solution to provide secure and reliable communication in atmosphere. This paper investigates the effect of pointing error on the performance of QKD communication systems. The analytical solution of error and sift probabilities, quantum bit error rate (QBER) and secret key rate (SKR) are obtained depending on pointing error effect that is modeled by Rayleigh and Hoyt distributions. Our findings show that the increased beam waist, hence the increased pointing error, degrades the performance of QKD communication systems remarkably. Also, the symmetric pointing error, where horizontal and vertical pointing errors are equal, yields worse performance for QKD systems as compared to the asymmetric pointing error case where vertical and horizontal pointing errors are different. The undeniable effect of pointing error on the performance of QKD system highlights the importance of precise beam alignment to minimize the adverse effects of pointing errors, thereby ensuring the secure and efficient operation of QKD systems in various deployment scenarios.

DOI
10.1109/jqe.2025.3627887

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Recently, quantum key distribution (QKD) has emerged as a prominent solution to provide secure and reliable communication in atmosphere. This paper investigates the effect of pointing error on the performance of QKD communication systems. The analytical solution of error and sift probabilities, quantum bit error rate (QBER) and secret key rate (SKR) are obtained depending on pointing error effect that is modeled by Rayleigh and Hoyt distributions. Our findings show that the increased beam waist, hence the increased pointing error, degrades the performance of QKD communication systems remarkably. Also, the symmetric pointing error, where horizontal and vertical pointing errors are equal, yields worse performance for QKD systems as compared to the asymmetric pointing error case where vertical and horizontal pointing errors are different. The undeniable effect of pointing error on the performance of QKD system highlights the importance of precise beam alignment to minimize the adverse effects of pointing errors, thereby ensuring the secure and efficient operation of QKD systems in various deployment scenarios.
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We devoted to analyzing information transfer in quantum channels in terms of the performance of quantum key distribution (QKD) free-space optical (FSO) communication systems through Bennett and Brassard 84 (BB84) protocol by taking into account the combined effect of attenuation, turbulence, pointing error, and angle of arrival (AOA) fluctuations. Path loss is modeled by Beer-Lambert law, and the turbulent channel is assumed to be Fisher-Snedecor F distributed. The pointing error and AOA fluctuations are modeled by Hoyt and Rayleigh distributions, respectively. The error and sift probabilities, quantum bit error rate, and secret key rate of a QKD FSO system are obtained in analytical form, and results are presented depending on various parameters. It is shown that increased beam waist, beam deviation, AOA fluctuations, and propagation distance cause performance degradation and less secure information transmission. However, an increase in the ratio of horizontal and vertical beam misalignments, field of view, average photon number per pulse, visibility of the atmospheric environment, and optical beam wavelength impact the performance of QKD FSO systems positively. The effect of the turbulence structure constant is observed to be modest on the performance of the QKD FSO system.
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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.
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.
Quantum Key Distribution (QKD) is a prominent solution to achieve proven secure data transmission between legitimate users despite any assumptions about the eavesdropper's computational power (given that the laws of quantum mechanics are correct). This remains true even under attacks by quantum computers. In recent years, there has been a great research interest in developing enhanced security constructions based on QKD. This is mainly driven by the envisioned threats of quantum computers to the traditional information security infrastructure based on public key cryptography. This research lies under the wide umbrella of the so-called post-quantum cryptography. However, for any QKD protocol, an accurate estimation of the Quantum Bit Error Rate (QBER) before the information reconciliation phase is crucial for both the efficiency and security perspectives. In spite of the importance of the QBER estimation step, the state-of-the-art literature still lacks a detailed investigation of the practical aspects of this issue. Therefore, this work aims to fill this research gap. An extension of the EnQuad simulator has been used to study the effect of QBER estimation on the efficiency and security of the BB84 QKD protocol for depolarizing quantum channels and individual Intercept/Resend Eve attacks. Various parameters affecting the QBER estimation process have been carefully investigated. Our evaluation has shown the significant importance of the QBER estimation step. Indeed, an empirical formula has been derived for calculating the required size of the sifted key subset (the so-called sharing rate) needed for the QBER estimation. This is a major contribution of the presented work.