This paper proposes a scheme for secure authentication of classical messages with single photons and a hashed function. The security analysis of this scheme is also given, which shows that anyone cannot forge valid message authentication codes （MACs）. In addition, the lengths of the authentication key and the MACs are invariable and shorter, in comparison with those presented authentication schemes. Moreover, quantum data storage and entanglement are not required in this scheme. Therefore, this scheme is more efficient and economical.
A multiparty simultaneous quantum identity authentication protocol based on Creenberger-Horne-Zeilinger （GHZ） states is proposed. The multi-user can be authenticated by a trusted third party （TTP） simultaneously. Compared with the scheme proposed recently （Wang et al 2006 Chin. Phys. Lett. 23（9） 2360）, the proposed scheme has the advantages of consuming fewer quantum and classical resources and lessening the difficulty and intensity of necessary operations.
Utilizing a three-particle W state, we come up with a protocol for the teleportation of an unknown two-particle entangled state. It is shown that the teleportation can be deterministically and exactly realized. Moreover, two-particle entanglement teleportation is generalized to a system consisting of many particles via a three-particle W state and a multi-particle W state, respectively. All unitary transformations performed by the receiver are given in a concise formula.
We present a new fair blind signature scheme based on the fundamental properties of quantum mechanics. In addition, we analyse the security of this scheme, and show that it is not possible to forge valid blind signatures. Moreover, comparisons between this scheme and public key blind signature schemes are also discussed.
A quantum secure direct communication protocol with cluster states is proposed.Compared with the deterministic secure quantum communication protocol with the cluster state proposed by Yuan and Song(Int.J.Quant.Inform.,2009,7:689),this protocol can achieve higher intrinsic efficiency by using two-step transmission.The implementation of this protocol is also discussed.
An efficient quantum secure direct communication protocol is presented over the amplitude damping channel.The protocol encodes logical bits in two-qubit noiseless states,and so it can function over a quantum channel subjected to collective amplitude damping.The feature of this protocol is that the sender encodes the secret directly on the quantum states,the receiver decodes the secret by performing determinate measurements,and there is no basis mismatch.The transmission's safety is ensured by the nonorthogonality of the noiseless states traveling forward and backward on the quantum channel.Moreover,we construct the efficient quantum circuits to implement channel encoding and information encoding by means of primitive operations in quantum computation.
We show a scheme to distribute the entanglement by using three-mode separable Gaussian state prepared with imperfect equipments. The scheme achieves the aim that the entanglement is distributed between two distant parties with only Gaussian operations and linear optics elements. Moreover, we analyse the logarithmic negativity of the entanglement shared between the two parties when the systems are imperfect and arrive at the conclusion that the logarithmic negativity is asymptotically stable with fluctuations within a certain space range.
Two simple quantum broadcast communication schemes are proposed. A central party can broadcast his secret message to all the legitimate receivers simultaneously. Compared with the three schemes proposed recently （Wang et al. 2007 Chin. Phys. 16 1868）, the proposed schemes have the advantages of consuming fewer quantum and classical resources, lessening the difficulty and intensity of necessary operations, and having higher efficiency.
Based on x-type entangled states and the two-step protocol [Deng F G, Long G L and Liu X S 2003 Phys. Rev. A 68 042317], a quantum secret sharing protocol of secure direct communication based on x-type entangled states ｜X00〉3214 is proposed. Using some interesting entanglement properties of this state, the agent entirety can directly obtain the secret message from the message sender only if they collaborate together. The security of the scheme is also discussed.
