A 15-user quantum secure direct communication network
Zhantong Qi, Yuanhua Li, Yiwen Huang, Juan Feng, Yuanlin Zheng, Xianfeng Chen
Quantum secure direct communication (QSDC) based on entanglement can directly
transmit confidential information. However, the inability to simultaneously
distinguish the four sets of encoded entangled states limits its practical
application. Here, we explore a deterministic QSDC network based on time-energy
entanglement and sum-frequency generation. 15 users are in a fully connected
QSDC network, and the fidelity of the entangled state shared by any two users
is greater than 97%. The results show that when any two users are performing
QSDC over 40 kilometers of optical fiber, the fidelity of the entangled state
shared by them is still greater than 95%, and the rate of information
transmission can be maintained above 1Kbp/s. Our Letter demonstrates the
feasibility of a proposed QSDC network, and hence lays the foundation for the
realization of satellite-based long-distance and global QSDC in the future.