Research Paper: Study of Thermal Entanglement and Teleportation in Spin-star Networks in Heisenberg XXX Model

In this paper, thermal entanglement in four and five-qubit spin-star networks evolved by an XXX Hamiltonian model is studied. We examine the effect of temperature, magnetic field and coupling constant on the concurrence. We will show that the entanglement is decreased by increasing the temperature and the number of qubits. Also, we investigate quantum teleportation via a couple of spin-star networks in a thermal state. The average of fidelity as a function of temperature, magnetic field, and coupling constant is analyzed, too. It will be observed that as the temperature increases, the fidelity first decreases and then tends to a constant value. Moreover, with the increase of the external magnetic field, the average fidelity first increases and then gradually decreases, and in a certain amount of magnetic field, the average fidelity becomes zero. In addition, as the number of qubits increases, fidelity decreases with temperature. The results indicate that mean fidelity increases with increasing coupling constant.