Nonclassical features of an open qubit cavity QED system - Research paper

Sep 30, 2026

Nonclassical features in an open quantum two-qubit cavity-QED configuration are studied by analyzing quantum correlations and measurement uncertainty under resonant and off-resonant conditions, with equal and unequal qubit–cavity coupling strengths. The work incorporates asymmetric qubit relaxation and dephasing together with cavity decay, showing cases where separable initial states outperform entangled ones for longer correlation preservation. A trade-off is identified among quantum correlations, measurement uncertainty, and mutual information, including irregular oscillations enabled by parameter asymmetries, and a quantum speed limit assessment of resourcefulness.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages16

Reading Time40 min

AccessFree to download

Introduction

Open quantum systems and information loss

Correlation measures: discord and mutual information

Problem formulation

Geometric quantum discord (GQD)

Quantum mutual information (MI)

Uncertainty relations and quantum memory

[www. nature.com/scientificreports](www. nature.com/scientificreports) OPEN Nonclassical features of an open qubit cavity QED system Abbas Manan1, Atta ur Rahman2, HamidArianZad3, Hazrat Ali4􀀍, AsadAli5, Saif Al-Kuwari5 & Saeed Haddadi6􀀍 We investigate the dynamics of quantum correlations and measurement uncertainty in a two-qubit system coupled to a cavity-QED system, characterized by various parameters such as qubit and cavity frequencies under resonant and off-resonant conditions, with equal and unequal coupling strengths. We emphasize asymmetric qubit relaxation and dephasing mechanisms, accompanied by cavity decay. In certain scenarios, separable initial states can outperform entangled states in maintaining quantum correlations over longer periods. We further uncover a trade-off between quantum correlations, measurement uncertainty, and mutual information. Additionally, we demonstrate that asymmetries in coupling strengths or qubit frequencies can enhance quantum correlations and induce irregular oscillations, suggesting new strategies for engineering robust quantum resources in open quantum systems. In comparison, we find that qubit relaxation leads to less decay than qubit dephasing. In contrast, quantum correlations are preserved much longer with appropriate tuning of the cavity decay rate. Finally, the concept of quantum speed limit is employed to assess the resourcefulness of our configuration. Keywords Cavity-QED system, Resonant and off-resonant coupling, Measurement uncertainty, Quantum speed limit, Open quantum systems Isolated quantum systems provide an ideal framework for studying quantumness or nonclassical features. However, in practical quantum information processing, quantum systems are often influenced by their surrounding environment1. In practice, quantum systems inevitably interact with their environment, leading to non-unitary dynamics that deviate from ideal unitary evolution2,3. The study of the dynamics, dynamical behaviors, and strategies of open quantum systems to avoid information loss is one of the most debated topics in quantum information science4–7. Although such interactions present challenges, they are essential for the advancement of quantum technologies and associated protocols, including communication, sensing, and computing8. In general, theoretical investigations lead to achieving optimal control of the system-environmental couplings, which in turn would be helpful to develop robust quantum protocols with higher efficiency in the quantum practical world. The open quantum system approach offers a realistic model for quantum systems that interact with their environment, leading to decoherence and the loss of quantum information9, 10. To address the challenges inherent in open quantum systems, several strategies have been proposed, including tracing out the environment or cavity degrees of freedom to obtain reduced dynamics11, employing optimal parameterizations ofthe system–environment interaction12, and engineering symmetric or asymmetric couplings that can induce or preserve quantum correlations13, 14. The utility of open quantum systems largely depends on the degree to which they maintain quantum correlations, with coherence serving as one of the most fundamental correlations15–17. While coherence quantifies superposition within a preferred basis, a complete characterization of quantumness requires examining how correlations are distributed between subsystems. This naturally leads to some measures like quantum discord, which captures non-classical correlations beyond entanglement. Geometric quantum discord (GQD) plays a significant role in understanding the behavior of quantum systems and the associated resourcefulness18 as it measures non-classical correlations between subsystems that persist 1School of Physics and State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 611731, China.

FAQs

What key trade-offs and control effects are reported?

The paper reports a trade-off between quantum correlations, measurement uncertainty, and mutual information, and shows that asymmetries in coupling strengths or qubit frequencies can enhance correlations and produce irregular oscillations.

Sep 30, 2026

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