Four classes of new entanglement-assisted quantum optimal codes

Entanglement-assisted quantum error-correcting codes (EAQECCs) provide a general framework for quantum code construction, which overcome certain self-orthogonal restriction. It becomes one main task in quantum error-correction to find EAQECCs with good parameters, especially entanglement-assisted quantum maximum distance separable (EAQMDS) codes. In this work, we construct four new families of EAQECC codes with flexible parameters in view of negacyclic codes. It is worth pointing out that those EAQECCs are EAQMDS codes when d <=(n+2)/2. By exploring the selection of defining sets, the constructed EAQECCs possess larger minimum distance in contrast with the known results in the literatures.