Entanglement fidelity of channel adaptive quantum codes

We study the performances of quantum channel adaptive 4,1 code transmitting in a joint amplitude damping and dephasing channel, the 6,2 code transmitting in an amplitude damping channel by combining the encoding, noise process, and decoding as one effective channel. We explicitly obtain the entanglement fidelities. The recovery operators of the 6,2 code are given. The performance is nearly optimal comparing with that of the optimal method of semidefinite programming.