Man Zhong-Xiao

Quantum Bidirectional Secure Direct Communication via Entanglement Swapping

In light of a quantum secure direct communication (QSDC) scheme using entanglement swapping [Chin. Phys. Lett. 22 (2005) 18], by introducing additional local operations for encoding, we propose a bidirectional QSDC (BQSDC) protocol, in which two legitimate users can simultaneously exchange their respective messages. The rule for the users to retrieve his/her partners messages is derived explicitly in the most general case. Eves commonly used attack method has been discussed and can be detected with the security checking process.

Controlled Bidirectional Quantum Direct Communication by Using a GHZ State

A controlled bidirectional quantum secret direct communication scheme is proposed by using a Greenberger–Horne–Zeilinger (GHZ) state. In the scheme, two users can exchange their secret messages simultaneously with a set of devices under the control of a third party. The security of the scheme is analysed and confirmed.

Continuous-Variable Quantum Teleportation of Entangled Coherent States

We propose a quantum teleportation scheme for tripartite entangled coherent state (ECS) with continuous variable. Our scheme is feasible and economical in the sense that we need only linear optical devices such as beam splitters, phase shifters and photon detectors and employ three bipartite maximally ECSs as quantum channels. We also generalize the tripartite scheme into multipartite case and calculate the minimum average fidelity for the schemes in tripartite and multipartite cases.

Quantum secure direct communication via partially entangled states

We present in this paper a quantum secure direct communication (QSDC) protocol by using partially entangled states. In the scheme a third party (Trent) is introduced to authenticate the participants. After authentication, Alice can directly, deterministically and successfully send a secret message to Bob. The security of the scheme is also discussed and confirmed.

Controlled Quantum N-Party Simultaneous Direct Communication

In this paper, we propose a controlled quantum N-party simultaneous direct communication protocol with single-qubit measurements. Many users can simultaneously exchange their secret messages in a set of devices with the control of a supervisor. The eavesdroppers commonly used attacks can be detected through two security checking processes.

Efficient One-Sender Versus N-Receiver Quantum Secure Direct Communication

An efficient quantum secure direct communication protocol with one-sender versus N-receiver is proposed. The secret bits can be encoded in the N+1-particle GHZ states and can be decoded by the N receivers with a classical information of the sender plus their own measurement outcomes. Any attacks can be detected by comparing measurement results on the detecting states.

A study on entanglement dynamics for a four-qubit model

In this paper, we consider the entanglement dynamics of a four-qubit model [2006 Phys. Rev. A 74 042328] where two entangled qubits a and b locally interact with separate qubits A and B via the spin-exchange-like Hamiltonian. We study the effect of purity of initial entangled state of qubits a, b on the entanglement evolution and its relation with energy transfer. Also, we find that the total bipartite entanglement of qubits a, b plus A, B is not a constant any longer when the initial entangled state of a, b is not pure, which is a complement to the result in the paper [2007 J. Phys. B 40 S45] for the pure case.

On entanglement invariant for a double Jaynes–Cummings model

In a recent paper [Phys. Rev. A 76 042313 (2007)], Sainz and Bjork introduced an entanglement invariant E under evolution for a system of four qubits interacting through two isolated Jaynes–Cummings Hamiltonians. This paper proves that this entanglement invariant E is closely connected with the linear entropy between two independent subsystems.