Teleportation via an Entangled Coherent Channel and Decoherence Effect on This Channel

We study an entangled two-mode coherent state within the framework of 2×2-dimensional Hilbert space. We investigate the problem of quantum teleportation of a superposition coherent state via an entangled coherent channel. By three different measures with the titles ``minimum assured fidelity (MASF)”, ``average teleportation fidelity” and ``optimal fidelity (f)” we study the quality of this kind of teleportation. Decoherence properties of the entangled coherent state due to channel losses are analysed. For a symmetric noise channel, the degradation of optimal fidelity and degree of entanglement are calculated. Also by two different measures with the titles ``concurrence” and ``entanglement of formation” we study the amount of entanglement of a decohered quantum channel and discuss its details. We demonstrate that entanglement of the decohered entangled coherent state is reduced but not throughly lost. Finally we find that the optimal fidelity of the decohered entangled coherent state is more than the classical limit and the decohered entangled coherent state may be useful for quantum teleportation.