Minimum Cost Swapping and Purification Scheduling Over Quantum Repeater Chains
Jiyao Liu, Lei Fan, Yuanxiong Guo +2 more
Entanglement swapping and purification are two fundamental primitives for long-distance entanglement distribution in quantum networks, enabling key applications such as quantum key distribution, quantum sensing, and distributed quantum computing. While prior work has established that purification should precede swapping in Binary systems to minimize the expected number of consumed link-level entanglements for an E2E fidelity guarantee, the critical problem of finding the optimal swapping and purification strategy remains open. To fill this gap, we study the Optimal Swapping and Purification Tree (OSPT) problem for a quantum repeater chain in Binary systems and derive the exact optimal solution. By leveraging the associativity of swapping and purification fidelity, we decompose the problem into three subproblems: optimal swapping tree construction, optimal purification scheduling, and global budget allocation. We show that although the exact solution can be obtained via brute-force search over budget distributions, its complexity grows exponentially. To address this challenge, we further propose an efficient greedy budget allocation algorithm. Extensive evaluations demonstrate that the greedy algorithm closely approximates the optimal solution and outperforms existing solutions while significantly reducing computational complexity.
International Conference on Quantum Communications, Networking, and Computing (QCNC)•Apr 6, 2026•0 citations