DETERMINISTIC SECURE QUANTUM COMMUNICATION WITH FOUR-QUBIT W STATES
Hao Yuan, Jun Song, Xiangyuan Liu, Shan Jen Cheng, Kui Hou, Lian-Fang Han · International Journal of Quantum Information · 2011
We propose a new protocol for deterministic secure quantum communication with a four-qubit W state. In this protocol, by using four local two-particle unitary operations and Bell basis measurements, the two legitimate users can directly transmit secret messages after exchanging some additional classical information. It will be shown that our protocol has a high capacity as each W state can carry two bits of secret information, and has a high intrinsic efficiency because almost all the instances are useful. Furthermore, this protocol is feasible with present day techniques.