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Laser Physics

Local quantum uncertainty in a two-qubit system due to classical environmental noise

Qinglong Tian, You-neng Guo

Published Oct 2, 2020• 3 citations
Publisher

Abstract

Abstract In this paper, we address the dynamics of nonclassical correlation, quantified by local quantum uncertainty (LQU) in a two-qubit system subjected to classical environmental noise when the initial states of system are prepared in a specific class of Bell states. Two different configurations of the local noisy environment are examined. In the first case, we consider a system of two independently qubits, each locally interacting with its classical random noise, whereas in the second case we consider only one of qubits subject to a classical random noise. Our results show that the dynamics of LQU is strongly related to both the dephasing and relaxation factors. The behaviors of LQU in above two cases exhibit similar variation, with monotonic decay in the weak coupling region, while revivals in the strong coupling region depending on the ratio of the switching rate and coupling strength to the qubit. By controlling this ratio, long-time survival of LQU is obtained. Therefore, our results may open an interesting perspective in using of the long-time survival of quantum correlations for practical applications in quantum information science.

DOI
10.1088/1555-6611/abb768

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Abstract In this paper, we address the dynamics of nonclassical correlation, quantified by local quantum uncertainty (LQU) in a two-qubit system subjected to classical environmental noise when the initial states of system are prepared in a specific class of Bell states. Two different configurations of the local noisy environment are examined. In the first case, we consider a system of two independently qubits, each locally interacting with its classical random noise, whereas in the second case we consider only one of qubits subject to a classical random noise. Our results show that the dynamics of LQU is strongly related to both the dephasing and relaxation factors. The behaviors of LQU in above two cases exhibit similar variation, with monotonic decay in the weak coupling region, while revivals in the strong coupling region depending on the ratio of the switching rate and coupling strength to the qubit. By controlling this ratio, long-time survival of LQU is obtained. Therefore, our results may open an interesting perspective in using of the long-time survival of quantum correlations for practical applications in quantum information science.
In this paper, the dynamics of quantum correlation quantified by local quantum uncertainty (LQU) and local quantum Fisher information (LQFI) for two uncoupled qubits driven by classical phase noisy laser have been investigated. The results show that, both LQU and LQFI exhibit similar behaviours, either display exponential decay or oscillatory decay with revivals depending on the ratios of classical phase noisy laser rate and system-environment coupling strength. Beside, our results also confirm the amount of quantum correlation measured by LQU is strictly bounded by LQFI in an open system. Finally, we propose a scheme to protect quantum correlation against classical phase noisy laser with the technique of weak measurement and reversal.
Abstract Recently, local quantum uncertainty (LQU) as a measure of quantum correlations has been proposed by Girolami et al . We here have investigated the LQU dynamics in a pair of qubits system subjected to either local or collective classical phase noises. The explicit analytical expressions of LQU for the two-qubit system of interest initially in a Werner state under these dephasing noises have been derived. We compare the dynamics of LQU with that of entanglement as measured with concurrence. Our results show that LQU always decays asymptotically while the entanglement displays sudden death phenomenon. Besides, there is no simple relation between the LQU and entanglement since LQU may be smaller or larger than entanglement. Finally, we try to protect LQU against the dephasing noise by means of filtering operation.
Abstract Quantum correlation plays an important role in quantum information processing, for which various quantifiers have been proposed so far. In this paper, we address the dynamics of local quantum uncertainty (LQU) as a reliable quantifier of quantum correlation in a two-qubit Heisenberg spin chain in the presence of nonuniform external magnetic field and Dzyaloshinski-Moriya interaction with intrinsic decoherence. The influences of the initial states, external magnetic field strength, Dzyaloshinski-Moriya interaction strength and intrinsic decoherence rate on the dynamics of LQU have been in detail investigated. Our analytical results show that the dynamics of LQU is strongly depended on the form of initial states. For an initial correlated state, the dynamical behaviors of LQU exhibit either monotonic decay or damped oscillations with respect to time. While for an initial separable state, quantum correlation quantified by LQU can be created due to the Dzyaloshinski-Moriya interaction and Heisenberg anisotropic interaction. Besides, the relationship between LQU and l -norm coherence or concurrence is also demonstrated in the present model.
Correlations in open quantum systems exhibit peculiar phenomena under the effect of various sources of noise. Here, we investigate the dynamics of entanglement and quantum discord (QD) for three noninteracting qubits coupled with a classical environmental static noise characterized by an external random field. Two initial entangled states of the system are examined, namely, the GHZ- and [Formula: see text]-type states. The system-environment interaction is here analyzed in three different configurations, namely, independent, mixed and common environments. We find that the dynamics of quantum correlations are strongly affected by the type of system-environment interaction and the purity of the initial entangled state. Indeed, depending on the type of interaction and the value of the purity of the initial state, peculiar phenomena such as sudden death, revivals and long-time survival of quantum correlations are observed. On the other hand, our results clearly show that quantum correlations initially present in the [Formula: see text]-type states are less robust than those of the GHZ-type states. Furthermore, we find that the long-time survival of entanglement can be detected by means of the suitable entanglement witnesses.
We address the effect of classical noise on the dynamics of quantum correlations, entanglement and quantum discord (QD), of two non-interacting qubits initially prepared in a Bell state. The effect of noise is modeled by randomizing the single-qubit transition amplitudes. We address both static and dynamic environmental noise corresponding to interaction with separate and common baths in either Markovian and non-Markovian regimes. In the Markov regime, a monotone decay of the quantum correlations is found, whereas for non-Markovian noise sudden death and revival phenomena may occur, depending on the characteristics of the noise. Entanglement and QD show the same qualitative behavior for all kind of noises considered. On the other hand, we find that separate and common environments may play opposite roles in preserving quantum correlations, depending on the noise regime considered.
In this paper, we analytically explore two qubits interacting with a coherent harmonic oscillator field under intrinsic noise. The interaction of the uncorrelated two qubits with a harmonic oscillator initially in the superposition of coherent states leads to the generation of nonclassical correlations (NCCs). The NCCs are quantified by local quantum uncertainty (LQU), uncertainty-induced non-locality (UIN), concurrence and Bell’s inequality. It is found that the generated NCCs are enhanced via the intensity coherence and the parameters of the initial harmonic oscillator state. For the even coherent state, the generated NCCs are more robust against the influence of intrinsic noise rate than that the ones of the coherent state. The appearance of the special type of skew-information correlation (in which, LQU and UIN are equal) depends on the superposition of the coherent states. The phenomena of sudden death and birth of entanglement depend not only on the intrinsic noise rate but also on the initial harmonic oscillator field. The generated NCCs could be controlled by adjusting these parameters.