Mixed Entangled Coherent Channel for Quantum Information Processing

We study an entangled two-mode coherent state within the framework of $2\times 2$ dimensional Hilbert space and suggest a scheme to teleport a coherent superposition state. When the entangled coherent state decays into the vacuum, it is found that its evolved state always remains entangled and the larger the coherent amplitude, the faster entanglement decreases. We find that the decohered entangled coherent state can be useless in quantum teleportation as it gives the optimal fidelity of teleportation less than the classical limit 2/3.