Angular Rejection Filtering Achieves Enhanced Security for Continuous-Variable Quantum Communications

Secure communication relies increasingly on quantum key distribution, and continuous-variable quantum key distribution (CVQKD) offers a promising route for free-space optical links, though vulnerabilities to turbulence, misalignment, and signal leakage currently limit its effectiveness.

Mohammad Taghi Dabiri, Meysam Ghanbari, Rula Ammuri, et al. from Hamad Bin Khalifa University and Qatar University now demonstrate a significant advance in CVQKD security by modelling and analysing a system incorporating an angular rejection filter. This filter establishes a safe zone at the receiver, blocking potentially compromised signals arriving from outside a defined angle, and the team’s detailed analysis reveals how careful optimisation of beam size, angular thresholds, and aperture dimensions dramatically reduces information leakage. The research highlights the crucial role of safe-zone enforcement and parameter tuning in achieving practical and secure quantum communication over free-space optical channels, paving the way for more robust and reliable quantum networks. Free-Space CV-QKD for UAV and Satellite Links This research pioneers a comprehensive system for continuous-variable quantum key distribution (CV-QKD) over free-space optical links, addressing critical vulnerabilities to turbulence, pointing errors, and eavesdropping attempts. Scientists engineered a receiver equipped with an Angular Rejection Filter positioned to define a safe-zone, blocking signals arriving from outside a desired angle and limiting information leakage.

The team developed a system and channel model that jointly captures the effects of atmospheric turbulence, random pointing errors, and the safe-zone, allowing for precise evaluation of security and performance.,. Safe-Zone Filter Boosts Free-Space QKD Security Scientists have achieved a significant breakthrough in continuous-variable quantum key distribution (CV-QKD) for free-space optical links by demonstrating the effectiveness of a novel “safe-zone” enforcement technique. The research team developed a comprehensive system and channel model that accurately captures the combined effects of atmospheric turbulence, pointing errors, and the newly implemented safe-zone filter. This model allows for precise evaluation of security metrics and optimization of system parameters. Experiments reveal that the safe-zone filter substantially reduces information leakage by blocking signals arriving from outside a defined angular cone.

The team derived information-theoretic expressions for mutual information, enabling detailed analysis of the system’s performance under various conditions.

Results demonstrate that careful tuning of the beam waist, angular threshold, and aperture size is essential for maximizing the secret key rate.,. Free-Space CVQKD Security With Safe Zones This research demonstrates that enforcing a safe zone at the receiver, coupled with careful parameter optimization, significantly enhances the security of continuous-variable quantum key distribution (CV-QKD) systems operating over free-space optical links. By modelling turbulence, misalignment, and the effects of a safe zone, the team developed metrics to evaluate security and demonstrated that simply maximizing signal reception is insufficient; the optimal angular threshold must be chosen to maximize the secret key rate and ensure reliable, secure communication. The findings reveal a clear trade-off between link distance, aperture size, and system performance. Longer links experience increased angular jitter and leakage, reducing the achievable key rate unless tighter angular control is implemented. However, increasing the aperture size demonstrably improves performance by increasing the maximum achievable key rate and allowing for wider beams and looser angular thresholds without compromising security. Simulations show that careful tuning of the beam waist and angular threshold is essential to maintain a secure region, particularly over extended distances.,. Free-Space CVQKD Security With Safe Zones This research demonstrates that enforcing a safe zone at the receiver, coupled with careful parameter optimization, significantly enhances the security of continuous-variable quantum key distribution (CV-QKD) systems operating over free-space optical links. By modelling turbulence, misalignment, and the effects of a safe zone, the team developed metrics to evaluate security and demonstrated that simply maximizing signal reception is insufficient; the optimal angular threshold must be chosen to maximize the secret key rate and ensure reliable, secure communication. The findings reveal a clear trade-off between link distance, aperture size, and system performance. Longer links experience increased angular jitter and leakage, reducing the achievable key rate unless tighter angular control is implemented. However, increasing the aperture size demonstrably improves performance by increasing the maximum achievable key rate and allowing for wider beams and looser angular thresholds without compromising security. Simulations show that careful tuning of the beam waist and angular threshold is essential to maintain a secure region, particularly over extended distances. 👉 More information 🗞 CV Quantum Communications with Angular Rejection Filtering: Modeling and Security Analysis 🧠 ArXiv: https://arxiv.org/abs/2512.18097 Tags: