Thermal Entanglement of Anisotropic XY Chains in a Transverse Field

By using the concept of concurrence, we numerically investigate the thermal entanglement between any two nearest-neighbour spins in uniform and periodic anisotropic XY chains in a transverse field at finite temperature T. It is found that the entanglement has more than one critical temperatures on some parameter regions for uniform and periodic chains. We also discuss the behaviour of the thermal entanglement at the vicinity of quantum phase transition of periodic anisotropic XY chains and find that a11 the derivatives aλC have similar behaviour as that of the uniform chain.     

Standard Teleportation of One-Qubit State and Partial Teleportation of Two-Qubit State via X-States

In this article,we derive the explicit entanglement and fidelity expressions for a larger class of two-qubit states,namely,a seven-parameter family of so called X-states.The analytical expressions of the entanglement,the output entanglement and the average fidelity are obtained for this general model by using the concept of concurrence and average fidelity.We study the relations between quantum entanglement,the output entanglement,and the average fidelity for standard teleportation of one-qubit and partial teleportation of two-qubit state.We discover that the average fidelity and entanglement is not a simple dependence relation.The higher entangled system is helpful for teleportation.