Optimal Calibration of Quantum Network Links

2026-06-16

AI Summary

This work addresses the trade-off between availability and fidelity in quantum networks, where link entanglement fidelity degrades under environmental disturbances. Focusing on calibration and activation scheduling for quantum repeater links, the authors formulate an optimization model that guarantees end-to-end fidelity constraints and extend it to general network topologies. Their key contributions include the first analytically derived optimal calibration strategy for linear repeater chains and an efficient heuristic algorithm for general networks that effectively handles the complex coupling constraints arising from shared links across multiple paths. Theoretical analysis and simulations demonstrate that the proposed approach achieves theoretical optimality in linear chains and significantly outperforms existing numerical benchmarks in general networks, closely approaching fundamental performance limits.

Abstract

The reliable distribution of entanglement is essential for the effective operation of quantum networks. Due to fundamental differences between quantum and classical communication systems, it is necessary to develop specialised algorithms and protocols that also account for quantum-specific constraints. In this work, we focus on the issue of recalibration. As suggested by recent experimental studies, the process of local entanglement generation in a quantum link degrades over time due to environmental changes that have to be estimated and compensated via a calibration operation, during which the link is not available. Therefore, in such a quantum network, every link alternates between an activation period, during which it operates normally, and a calibration period, during which it cannot participate in the end-to-end entanglement distribution, thereby creating a trade-off between link quality (the fidelity of generated pairs, which decays during activation) and availability (the fraction of time the link is usable, which calibration reduces). We develop analytically a protocol for optimally assigning activation periods to each link in linear quantum repeater chains, subject to any general end-to-end fidelity requirements and local initial fidelity thresholds. Building on this foundation, we extend to general quantum networks, where multiple paths may cross at common links, proposing a heuristic approach evaluated in simulations and compared with a benchmark, numerical approach, and theoretical bounds.

Problem

• quantum networks
• entanglement distribution
• link calibration
• fidelity decay
• availability trade-off

Innovation

• quantum network calibration
• entanglement distribution
• fidelity-availability trade-off
• optimal activation scheduling
• quantum repeater chain