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arXiv:2604.16236 · IEEE Transactions on Quantum Engineering

Long-term Performance Analysis of a Commercial QKD Device Under Real-world Deployment Conditions

Alisson Tezzin, Gustavo M. Uhdre, Oscar Martins, Sabrina Rufo, Vitor G. A. Carneiro

quant-phSubmitted Apr 17, 2026• Announced Apr 20, 2026• 0 citations• Revised May 19, 2026 (v2)
v1 · Apr 17, 2026v2 · May 19, 2026
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Abstract

Quantum key distribution (QKD) has reached a commercially viable stage, with several companies offering hardware systems designed for operational deployment. Evaluating the performance of commercial QKD devices under real-world deployment conditions is essential for users seeking to understand the practical limitations and operational reliability of these systems. In this paper, we present a long-term performance analysis of ID Quantique's Clavis XGR deployed within the Hermes Quantum Network, in Brazil. Our study provides a detailed characterization of key operational metrics, such as secret key rate, quantum bit error rate (QBER), visibility, and detection counts, mapping their behavior over extended periods of continuous operation. We analyze the system's stability across two distinct optical links: a 40.3 km indoor spooled fiber and a 3.5 km outdoor deployed underground fiber. Monitored under both unregulated tropical ambient fluctuations and actively controlled thermal stress, our results demonstrate excellent overall baseline resilience, with the system maintaining visibility above 97% and QBER below 1% on average. These findings provide practical insights into the expected behavior and thermal bottlenecks of commercial QKD systems in field deployments, particularly in tropical climates, helping to inform realistic expectations for operational quantum-safe infrastructures.

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12 pages and 20 figures

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Quantum key distribution (QKD) has reached a commercially viable stage, with several companies offering hardware systems designed for operational deployment. Evaluating the performance of commercial QKD devices under real-world deployment conditions is essential for users seeking to understand the practical limitations and operational reliability of these systems. In this paper, we present a long-term performance analysis of ID Quantique's Clavis XGR deployed within the Hermes Quantum Network, in Brazil. Our study provides a detailed characterization of key operational metrics, such as secret key rate, quantum bit error rate (QBER), visibility, and detection counts, mapping their behavior over extended periods of continuous operation. We analyze the system's stability across two distinct optical links: a 40.3 km indoor spooled fiber and a 3.5 km outdoor deployed underground fiber. Monitored under both unregulated tropical ambient fluctuations and actively controlled thermal stress, our results demonstrate excellent overall baseline resilience, with the system maintaining visibility above 97% and QBER below 1% on average. These findings provide practical insights into the expected behavior and thermal bottlenecks of commercial QKD systems in field deployments, particularly in tropical climates, helping to inform realistic expectations for operational quantum-safe infrastructures.
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The feasibility of a quantum-classical hybrid network using multicore fiber is explored and key performance metrics of the quantum channel with respect to co-propagating classical light are examined. Multiple commercial time bin quantum key distribution systems from ID Quantique are characterized using direct injection techniques to determine optimal operational parameters for the classical optical channels in order to minimize the quantum bit error rate and maximize secret key generation. A phenomenological model that determines the expected quantum bit error rate for a wide range of injected input wavelengths and powers is utilized to evaluate the quantum key distribution system performance. Analysis shows that the performance limitations exhibited by the tested commercial quantum key distribution systems in a hybrid network based on multicore fiber could be overcome by a strategic choice of the classical channel parameters.
The deployment of quantum-secure communication networks is facing rapid progress, however their practical implementation still presents significant challenges due to limited achievable distances, channel losses, resource constraints, and network imperfections. Focusing on single-click quantum key distribution (QKD) protocols, which are advantageous for their long-distance capabilities, we investigate their experimental requirements and system characteristics in the context of realistic network deployment. We provide a comprehensive assessment based on our current experimental status, anticipated improvements, different detection technologies, and channel asymmetries. We further discuss our experimental results obtained with a preliminary single-click QKD hardware implementation, showing an achievable communication distance of ~ 250 km, with the potential to extend this reach to ~ 500 km. We show that viable setup improvements enable even longer distances > 1000 km. Our analysis serves as a foundation for further evaluating the applicability of single-click QKD within an existing national quantum communication infrastructure, addressing key practical considerations such as link asymmetries and channel losses. Our study and results provide a solid foundation for the practical deployment of large-scale quantum communication networks, and highlight the potential of single-click QKD as a promising candidate in this direction.
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