  Through concurrence, we characterize the entanglement properties of optical
coherent-state qubits subject to an amplitude damping channel. We investigate
the distillation capabilities of known error correcting codes and obtain upper
bounds on the entanglement depending on the non-orthogonality of the coherent
states and the channel damping parameter. This work provides a first, full
quantitative analysis of these photon-loss codes which are naturally
reminiscent of the standard qubit codes against Pauli errors.
