Towards the World-Wide Quantum Network

Quantum Key Distribution (QKD) networks are of much interest due to their capacity of providing extremely high security keys to network participants. Most QKD network studies so far focus on trusted models where all the network nodes are assumed to be perfectly secured. This restricts QKD networks to be small. In this paper, we first develop a novel model dedicated to large-scale QKD networks, some of whose nodes could be eavesdropped secretely. Then, we investigate the key transmission problem in the new model by an approach based on percolation theory and stochastic routing. Analyses show that under computable conditions large-scale QKD networks could protect secret keys with an extremely high probability. Simulations validate our results.