We address the problem of encoding entanglement-assisted (EA) quantum error-correcting codes (QECCs) and of the corresponding complexity.We present an iterative algorithm from which a quantum circuit composed of CNOT,H,and S gates can be derived directly with complexity O(n～2) to encode the qubits being sent.Moreover,we derive the number of each gate consumed in our algorithm according to which we can design EA QECCs with low encoding complexity.Another advantage brought by our algorithm is the easiness and efficiency of programming on classical computers.
