Quantum key distribution protocol of mesh network structure based on n + 1 EPR pairs

Quantum key distribution (QKD) is used in quantum cryptographic systems to exchange secret key between parties who need to communicate secretly. According to the structure of European Secoqc QKD network, a QKD protocol is proposed. Entanglement swapping between Einstein-Podolsky-Rosen (EPR) pairs can be used to exchange message bits in two remote places. Based on this idea, n + 1 EPR pairs are used as logical quantum channel (for n nodes per routing), while measurements of Bell operator are transmitted by classical channel. Random space quantum channel selection is exploited in our protocol to improve the probability of revealing Eve. Compared with traditional EPR protocol, the proposed protocol exhibits many features, which are minutely described.