Abstract: As urban quantum networks expand beyond point-to-point links into multi-tenant meshes, dynamic routing protocols become essential. This paper details routing algorithms that balance optical path attenuation, key pool levels, and physical fiber cut risks in real time.
We formulate metropolitan quantum key allocation as a constrained multi-commodity flow optimization problem, solved in real time using linear programming. The algorithm minimizes end-to-end hop count while penalizing links experiencing high classical Raman background noise.
We extend standard BGP routing vectors with quantum metadata attributes, including available key volume (AKV), current QBER, and physical trusted node security certification levels. Autonomous systems use Q-BGP to negotiate inter-domain quantum-secured routes seamlessly.
Simulating a 30-node topology modeled on the London financial district confirms that Q-BGP dynamic routing improves aggregate key delivery throughput by 48% compared to static Dijkstra routing, completely preventing localized key pool exhaustion during financial market open hours.