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Laser Physics

Enhancement of quantum entanglement by local non-Hermitian operation under various decoherence sources

Qiong Wang, Lan Xu, Zhi He

Published Nov 19, 2020• 12 citations
Publisher

Abstract

Abstract We examine the validity and limitation of the local non-Hermitian operation in the enhancement of qubit-qubit entanglement from various decoherence sources. We derive the exact expressions of concurrence quantifying entanglement for an exactly solving model consisting of two qubits interacting with various decoherence sources. we show explicitly that the local non-Hermitian operation indeed helps for enhancing quantum entanglement from amplitude damping, but not for phase damping. Finally, we give a brief discussion of the physical explanation for our scheme.

DOI
10.1088/1555-6611/abc613

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We investigate entanglement of assistance without and with decoherence using a local non-Hermitian operation, i.e., parity–time ( P T ) 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 P T symmetric operation performed on one of two parties with the influence of noise is superior to that of P T 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 P T symmetric operation method may have potential applications in quantum decoherence control.
Abstract Entangled states with high-dimensional systems have been investigated widely because of their extended possibilities. We investigate the entanglement protection of a qubit–qutrit system under amplitude damping decoherence by employing non-Hermitian operation. We find that the qubit–qutrit entanglement decays monotonically as the decoherence strength increases, and may go through a sudden death for strong decoherence strength. However, we can completely defeat amplitude damping decoherence and recover or even magnify the initial entanglement perfectly by means of non-Hermitian operation. In particular, the non-Hermitian operation can protect entanglement more efficiently in the case of strong decoherence strength than those with small decoherence strength.
Abstract Using the non-Hermitian operation approach, we propose a scheme to protect and enhance entanglement from correlated amplitude damping decoherence. In contrast to the results of memoryless amplitude damping channel, we show that the memory effects play a significant role in the suppression of entanglement sudden death and induce the entanglement revival. Moreover, we find that the damaged entanglement can be effectively enhanced by using the non-Hermitian operation. Furthermore, the freezing phenomenon of entanglement can be detected by using the optimal non-Hermitian operation.
Abstract Protection of entanglement of two qubits undergoing two independent amplitude damping channels using a local parity-time ( PT ) symmetric operation is exactly studied. First, the explicit expressions of concurrence quantifying the entanglement of two qubits with both local PT symmetric operation and two amplitude damping channels are obtained. Then, we give two schemes, i.e. prior and post PT symmetric operations, to show the performance of PT symmetric operation on entanglement dynamics of two qubits. By investigation, we find that the effect of prior PT symmetric operation schemes on the protection of entanglement of two qubits in the double channel case is superior to that of the single channel case. Conversely, the effect of post PT symmetric operation scheme on the protection of entanglement of two qubits in the single channel case is better than that in the double channel case. In other words, the local PT symmetric operation approach may have potential applications in combating amplitude damping decoherence.