Xia Yun-Jie

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.

The problems of the nonlinear unsymmetrical bending for cylindrically orthotropic circular plate (II)

In this paper, the problems of nonlinear unsymmetrical bending for cylindrically orthotropic circular plate are studied by using “the method of two-variable”[1], and the uniformly valid asymptotic solutions of Nth-order for ε1 and Mth-order for ε2 are obtained

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.

Entanglement dynamics of a three-qubit system with different interatomic distances*

We investigate the tripartite entanglement dynamics of three two-level atoms in a multi-mode vacuum field. By considering the influences of the interatomic distance and the initial condition on the lower bound of concurrence and the tripartite negativity, we show that an optimal interatomic distance can be found to minimize the collective damping. Interestingly, at the same optimal distance, the tripartite entanglement would be maximized in the open dynamics process. In the case of shorter interatomic distance, the tripartite entanglement can display the oscillatory behavior in the initial short-time limit and be trapped in a stationary value in the long-time limit. In addition, the tripartite entanglement for the general situation with different interatomic distances is also discussed.

Entanglement Dynamics and Bell Violations of Two Atoms in Tavis–Cummings Model with Phase Decoherence

X iv :0 80 8. 37 09 v1 [ qu an tph ] 27 A ug 2 00 8 Entanglement dynamics and Bell Violations of two atoms in Tavis-Cummings model with phase decoherence ∗ C. J. Shan†,1 W. W. Cheng, 1 T. K. Liu‡,1 D. J. Guo, 2 and Y. J. Xia2 1College of Physics and Electronic Science, Hubei Normal University, Huangshi 435002, China 2Department of Physics, Qufu Normal University, Qufu 273165, China (Dated: August 27, 2008) Abstract Considering the dipole-dipole coupling intensity between two atoms and the field in the Fock state, the entanglement dynamics between two atoms that are initially entangled in the system of two two-level atoms coupled to a single mode cavity in the presence of phase decoh erence has been investigated. The two-atom entanglement appears with periodicity without considerin g phase decoherence, however, the phase decoherence causes the decay of entanglement between two atoms, with the increasing of the phase decoherence coefficient, the entanglement will quickly become a constan t v lue, which is affected by the two-atom initial state, Meanwhile the two-atom quantum state will forev er stay in the maximal entangled state when the initial state is proper even in the presence of phase decoher enc . On the other hand, the Bell violation and the entanglement does not satisfy the monotonous relation, a large Bell violation implies the presence of a large amount of entanglement under certain conditions, whi le a large Bell violation corresponding to a little amount of entanglement in certain situations. However, the violation of Bell-CHSH inequality can reach the maximal value if two atoms are in the maximal entangled st ate, or vice versa.Considering the dipole-dipole coupling intensity between two atoms and the field in the Fock state, the entanglement dynamics between two atoms that are initially entangled in the system of two two-level atoms coupled to a single mode cavity in the presence of phase decoherence has been investigated. The two-atom entanglement appears with periodicity without considering phase decoherence, however, the phase decoherence causes the decay of entanglement between two atoms, with the increasing of the phase decoherence coefficient, the entanglement will quickly become a constant value, which is affected by the two-atom initial state. Meanwhile the two-atom quantum state will forever stay in the maximal entangled state when the initial state is proper even in the presence of phase decoherence. On the other hand, the Bell violation and the entanglement do not satisfy the monotonous relation, a large Bell violation implies the presence of a large amount of entanglement under certain conditions, while a large Bell violation corresponds to a little amount of entanglement in certain situations. However, the violation of Bell-CHSH inequality can reach the maximal value if two atoms are in the maximal entangled state, or vice versa.

Phase modulation pseudocolor encoding ghost imaging

We present a ghost imaging scheme that can obtain a good pseudocolor image of black-and-white objects. The essential idea is to use a multi-wavelength thermal light source and the phase modulation pseudocolor encoding technique, which overcomes the disadvantages of other methods involved spatial filtering. Therefore, the pseudocolor ghost image achieved by this imaging scheme is better than that obtained by other methods in terms of brightness, color, and signal-to-noise ratio.