An Efficient Scheme for Multiparty Multi-particle State Sharing

We present an efficient scheme for sharing an arbitrary m-qubit state with n agents. In our scheme, the sender Alice first shares m Bell states with the agent Bob, who is designated to recover the original m-qubit state. Furthermore, Alice introduces n- 1 auxiliary particles in the initial state ｜0）, applies Hadamard （H） gate and Controlled-Not （CNOT） gate operations on the particles, which make them entangled with one of m particle pairs in Bell states, and then sends them to the controllers （i.e., other n - 1 agents）, where each controller only holds one particle in hand. After Alice performing m Bell-basis measurements and each controller a single-particle measurement, the recover Bob can obtain the original unknown quantum state by applying the corresponding local unitary operations on his particles. Its intrinsic efficiency for qubits approaches 100%, and the total efficiency really approaches the maximal value.     

Cryptanalysis of fair quantum blind signatures

We investigate the fair quantum blind signature scheme proposed by Wang and Wen [Wang T Y and Wen Q Y 2010 Chin.Phys.B 19 060307],which uses the fundamental properties of quantum mechanics and the availability of a trusted arbitrator.However,in this paper,we find that the protocol cannot satisfy the property of non-forgeability even under the condition that the trusted arbitrator is totally credible.Moreover,a simple feasible suggestion for improving the protocol is proposed.