Assuming there is a shared string between the users, we present a novel scheme, the lengthened string scheme (LSS), where the shared string is lengthened firstly by a specially designed algorithm, then some special treatments are applied on the lengthened one before it is used to authenticate. Based on the lengthened string scheme (LSS) we propose a quantum authentication protocol using entanglements. And the robustness of our protocol is discussed. In fact all the quantum key distribution protocols can do identification simultaneously based on the LSS.
GUO Fen-zhuo~(1,2), WEN Qiao-yan~1, ZHU Fu-chen~3 1.School of Science, Beijing University of Posts and Telecommunications, Beijing 100876, P.R. China
A scheme for teleporting an unknown two-particle entangled state is proposed. In comparison with the recent protocol （Cola et al., Phys. Lett. A 337 （2005））, the entangled state as quantum channel required by this scheme is a single, partially entangled pair, which is much easier to prepare and maintain. Furthermore, a positive operator valued measure （POVM） is adopted and all kinds of transformations performed by sender and receiver are given in detail. It is shown that the probability of successful teleportation is twice the modulus square of the smaller Schmidt coefficient of the two-particle entangled state, and the fidelity can reach one.
