Improving entanglement of assistance by local parity–time symmetric operation**Project supported by China Postdoctoral Science Foundation (Grant No. 2017M622582), the Natural Science Foundation of Hunan Province of China (Grant No. 2015JJ3092), the Research Foundation of Education Bureau of Hunan Province of China (Grant No. 16B177), Applied Characteristic Disciplines in Hunan Province-Electronic Science and Technology of China, and Hunan-Provincial Key Laboratory of

Abstract

We investigate entanglement of assistance without and with decoherence using a local non-Hermitian operation, i.e., parity–time () symmetric operation. First we give the explicit expressions of entanglement of assistance for a general W-like state of a three-qubit system under a local parity–time symmetric operation. Then for a famous W state without decoherence, we find that entanglement of assistance shared by two parties can be obviously enhanced with the assistance of the third party by a local parity–time symmetric operation. For the decoherence case, we provide two schemes to show the effects of local parity–time symmetric operation on improvement of entanglement of assistance against amplitude damping noise. We find that for the larger amplitude damping case the scheme of symmetric operation performed on one of two parties with the influence of noise is superior to that of symmetric operation performed on the third party without the influence of noise in suppressing amplitude damping noise. However, for the smaller amplitude damping case the opposite result is given. The obtained results imply that the local symmetric operation method may have potential applications in quantum decoherence control.