A high dimensional entanglement-based fully connected quantum key distribution network

Many field tests of quantum key distribution (QKD) have been implemented, which proves it to be a reliable technology. However, most of the implementations are limited to two parties. The ability to efficiently build cryptographic keys among multiple users can significantly extend the applications of QKD. Here, we propose and experimentally demonstrate a high-dimensional entanglement-based fully connected QKD network. In this architecture, a broadband entanglement photon pair source at telecom band is shared by end users via wavelength and space division multiplexing. The spectrum of entangled photon pairs is divided into 16 pairs of frequency-conjugate channels and each pair supports a subnet with 8 users by a passive beam splitter. What's more, high-dimensional encoding is applied in QKD network to utilize the entanglement resource efficiently. Eventually, we show that one entangled photon source can be shared over 100 users, and high-dimensional entanglement-based QKD could be realized between any two users.