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Laser Physics

Decoherence suppression with both spontaneous emission and dephasing by non-Hermitian operation

Li Ji-Xin, Lan Xu, Yun-Hui Zhao, Zhi He, Qiong Wang

Published Jun 18, 2021• 9 citations
Publisher

Abstract

Abstract Decoherence suppression from disturbance of the environment is an essential task in quantum information processing. Using the non-Hermitian operation approach, decoherence suppression of a qubit system interacting with a zero-temperature reservoir with both spontaneous emission and dephasing is investigated. We derive the exact analytical expressions of the quantum fidelity and find that quantum coherence can be significantly enhanced by controlling the non-Hermitian operator parameters. In particular, the non-Hermitian is more effective in the case of strong decay rates and show better inhibition effect on dephasing process than the spontaneous emission process.

DOI
10.1088/1555-6611/ac089d

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Abstract Decoherence suppression from disturbance of the environment is an essential task in quantum information processing. Using the non-Hermitian operation approach, decoherence suppression of a qubit system interacting with a zero-temperature reservoir with both spontaneous emission and dephasing is investigated. We derive the exact analytical expressions of the quantum fidelity and find that quantum coherence can be significantly enhanced by controlling the non-Hermitian operator parameters. In particular, the non-Hermitian is more effective in the case of strong decay rates and show better inhibition effect on dephasing process than the spontaneous emission process.
Decoherence suppression from disturbance of the environment is an essential task in quantum information processing. We investigate decoherence suppression of a qutrit system interacting with a zero-temperature reservoir with both spontaneous emission and dephasing by employing the weak measurement and reversal (WMR) operation. We find that the qutrit decoherence can be efficiently suppressed by solving the master equation of the qutrit system. In particular, WMR can completely suppress the decoherence in the case of strong decay rates.
Abstract Using a non-Hermitian operation approach, we propose a scheme to improve quantum dense coding of a qubit-qubit system interacting with a zero-temperature reservoir with both spontaneous emission and dephasing. By solving the master equation of the two-qubit system, we numerically obtain the final capacity of quantum dense coding. The numerical results show explicitly that the non-Hermitian operation indeed helps to improve the non-Hermitian operation from amplitude-phase decoherence. In particular, non-Hermitian operations can protect quantum dense coding more efficiently in the case of strong decay rates than those with small decay rates.
Decoherence is strongly influenced by environmental criticality, with conventional Hermitian critical points typically enhancing the loss of quantum coherence. Here, we show that this paradigm is fundamentally altered in non-Hermitian environments. Focusing on qubits coupled to non-Hermitian spin chains and interacting ultracold Fermi gases, we find that approaching exceptional points can either enhance or strongly suppress decoherence, depending on the balance between Hermitian and non-Hermitian system-environment couplings. In particular, when these couplings are comparable, decoherence is dramatically suppressed at exceptional transitions. We trace this behavior to the distinct response of the environmental ground state near non-Hermitian degeneracies and demonstrate the robustness of this effect across multiple models. Finally, we show that the predicted suppression of decoherence is directly observable on current digital quantum simulation platforms. Our results establish exceptional points as a concrete mechanism for suppressing decoherence and identify non-Hermitian criticality as a new avenue for coherence control in open quantum systems and quantum technologies.
Abstract Protection of entanglement from disturbance of the environment is an essential task in quantum information processing. We study the dynamic behaviours of quantum entanglement between two uncoupled qubits, which are immersed in a common phase decoherence environment. We examine the validity of the local non-Hermitian operation in the amplification of qubit–qubit entanglement. In particular, using analytical and numerical investigations, we show explicitly that the quantum entanglement of the two qubits can be greatly amplified by means of non-Hermitian operation.
Inevitable interaction between quantum system and environment will induce decoherence which would destroy the quantum coherence (QC) of quantum system. In this paper, we examine the QC behaviors for a single qubit locally coupled to the zero-temperature multiple bosonic reservoirs. Comparing the Markovian and non-Markovian QC behaviors, it is demonstrated that QC decays as decoherent time goes by, and non-Markovian QC exhibits obvious oscillating behaviors. The oscillatory frequency and amplitude increase with growing coupling strength and number of reservoirs. In addition, in non-Markovian regime, QC vanishes at some discrete critical time points. Finally, we reveal an effective method to suppress decoherence with filtering operation.
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.