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Laser Physics

The effects of non-Hermitian operators on entanglement in non-Markovian environments

Yang Leng, Wenjuan Li

Published Aug 28, 2020• 11 citations
Publisher

Abstract

Abstract The enhancement of qubit–qubit entanglement is systematically investigated by employing local non-Hermitian operations. Special attention is paid to the comparison of prior and post non-Hermitian cases. We derive the exact expressions of concurrence quantifying entanglement to arrive at an exact solution model, consisting of two qubits interacting with an independent structured reservoir. The results show that qubit–qubit entanglement can obviously be enhanced by means of either local prior or post non-Hermitian operations. In particular, we find that the effect of the prior non-Hermitian operator process of the double damping channels is superior to the post non-Hermitian process, while the effect of the single damping channel case shows the opposite trend.

DOI
10.1088/1555-6611/abaabd

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Abstract The enhancement of qubit–qubit entanglement is systematically investigated by employing local non-Hermitian operations. Special attention is paid to the comparison of prior and post non-Hermitian cases. We derive the exact expressions of concurrence quantifying entanglement to arrive at an exact solution model, consisting of two qubits interacting with an independent structured reservoir. The results show that qubit–qubit entanglement can obviously be enhanced by means of either local prior or post non-Hermitian operations. In particular, we find that the effect of the prior non-Hermitian operator process of the double damping channels is superior to the post non-Hermitian process, while the effect of the single damping channel case shows the opposite trend.
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.
Abstract In this work, we investigate effect of parity-time ( PT ) symmetric operation on the dynamic behavior of entanglement for two qubits system in Markovian and non-Markovian regimes with the resonant and off-resonant cases. First we derive the explicit expressions of concurrence quantifying entanglement for an exactly solving model consisting of two qubits interacting with independent structured reservoir. Then, we give two schemes, i.e. pre- 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 lower the absolute value of the PT operation strength, the better the enhancement of entanglement. In addition, we show that the entanglement can be obviously enhanced by means of the pre- PT symmetric operation in different regimes.
Abstract The dynamic behavior of the relative entropy of coherence for a two-level system is systematically investigated within non-Markovian environment. We derive the exact expressions of relative entropy quantifying coherence for an exactly solving model consisting of single qubit interacting with independent structured reservoir. By employing local non-Hermitian operation, i.e. parity-time ( PT ) symmetric operation, we show that the vanished quantum coherence can be effectively restored under the non-Markovian regimes. Furthermore, the freezing phenomenon of the coherence can be detected by using the optimal PT symmetric operation strength within the non-Markovian environments.
The dynamics of entanglement between two qubits in the local damping two-sided channel and single-sided channel are compared through non-Markovian process and Markovian process. The entanglement between two qubits is found to be longer in the single-sided channel case due to the weakening of the dissipative effects. In the two-sided channel, influenced by the entanglement between qubits, the previous independent dissipative channels incline to the composite effect of the Markovian process. This composite effect results in the dissipative effect of one channel affecting the qubits in the other channel, especially inhibiting the backflow effect in the non-Markovian channel, which is disadvantageous to the entanglement maintenance between qubits. In the Markovian channel, the composite effect of the damping two-sided channels is more obvious since there is no backflow effect, thus more disadvantageous to the entanglement maintenance.
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.
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.