Magnetic field effects on the optimal fidelity of standard teleportation via the two qubits Heisenberg XX chain in thermal equilibrium

We study the two qubits Heisenberg XX chain with magnetic impurity in the presence of the external magnetic field and calculate the optimal fidelity of standard teleportation via the thermal equilibrium state. It is found that the combined influence of magnetic impurity and external magnetic field can increase the critical temperatures of entanglement and quantum teleportation without limit. The relation between two kinds of critical temperatures is revealed.
8 pages, 3 figures