Quantum Computation and Information Seminar 

01/07/2011, 15:00 — 16:00 — Room P4.35, Mathematics Building
Daowen Qiu, SQIG, Instituto de Telecomunicações

Semi-quantum key distribution with less states and Semi-quantum secret sharing without entanglement

Boyer, Kenigsberg, and Mor [Phys.Rev.Lett.99, 140501(2007)] proposed a new semi-quantum key distribution with four states where a key can be securely distributed between Alice who can perform any quantum operation and Bob who works classically. We have proposed new protocols for semi-quantum key distribution with less than four states and their security has been analyzed in detail. Recently, this idea of "semi-quantumness" has been incorporated also to quantum secret sharing [Phys.Rev. A 82, 022303 (2010)], and a semi-quantum secret sharing protocol has been presented, where a quantum Alice, can share a secret key with two classical participants and they can collaborate to recover the secret, but none can do that alone. In the protocol, a three-particle maximally entangled state plays a crucial role. However, multipartite entangled states are generally difficult to prepare in experiments. Therefore, we also present a new protocol for semi-quantum secret sharing where a quantum participant can share a secret key with two classical participants without using any entanglement. The protocol is also showed to be secure against eavesdropping.