Routing and Wavelength Assignment for Entanglement Swapping in Photonic Quantum Networks

Abstract

Efficient entanglement routing in quantum data networks is essential for concurrently establishing as many entanglement connections as possible, maximizing network throughput. We consider networks with wavelength-division multiplexed quantum links where each quantum repeater performs entanglement swapping by directly measuring two photonic qubits from entangled photon sources on the same wavelength. To address unique challenges in achieving a high network throughput in such networks, we propose QuRWA to jointly optimize the entanglement routing and wavelength assignment. QuRWA introduces the Co-Path concept to improve fault-tolerance: we assign all entanglement links in a Co-Path set to the same wavelength, allowing them to serve as backup resources for other links within the same Co-Path during connection establishment. To exploit this redundancy, we design efficient algorithms to optimize the Co-Path selection and wavelength assignment to maximize resource utilization and fault tolerance. We further extend QuRWA to QuRWA-AO by adding all-optical switches at quantum nodes. This extension enables direct entanglement establishment between non-adjacent nodes through photonic Bell pair distribution across physical segments (interconnected physical links sharing wavelength consistency) while bypassing operations dependent on fiber delay lines at selected intermediate nodes. By reducing intermediate fiber delay line consumption, QuRWA-AO can admit additional feasible connections. Extensive simulations demonstrate that QuRWA improves throughput over schemes without the Co-Path abstraction or with sub-optimal wavelength assignment, and also maintains a consistent margin over a more advanced concurrent-routing baseline. By integrating all-optical switching, QuRWA-AO further improves throughput over QuRWA by 25.2% on average across the evaluation groups.