Entanglement protection induced by mixed noise

TL;DR

The paper addresses whether noise can be leveraged to protect entanglement in open quantum systems by analyzing a two-atom cavity QED model with quantum noise from cavity leakage and classical noise in atom–cavity couplings. It derives an HF-noise freezing mechanism analytically and validates it with numerical simulations across mixtures of Ornstein–Uhlenbeck, 1/f (flicker), and telegraph noises, showing that high-frequency content in the mixed noise suppresses decoherence from LF quantum noise. The key contribution is demonstrating that the HF fraction of the mixed classical noise, together with the constituent-noise properties and their mixing ratio, governs entanglement protection, yielding practical guidelines for noise-engineering to protect entanglement in realistic devices. The results offer a path toward noise-assisted mitigation of decoherence in open quantum systems, with potential impact on robust quantum information processing in cavity QED and related platforms.

Abstract

Contrary to the conventional view that noise is detrimental, we show that mixed noise can protect entanglement in a two-atom-cavity system. Specifically, the leakage of the cavity and the stochastic atom-cavity couplings are modeled as two types of noises. From the analytical derivation of the dynamical equations, the mechanism of the entanglement protection is revealed as the high-frequency(HF) noise in the atom-cavity couplings could suppress the decoherence caused by the cavity leakage, thus protect the entanglement. We investigate the entanglement protection induced by mixed noise constructed from diverse noise types, including the Ornstein-Uhlenbeck noise, flicker noise, and telegraph noise. Numerical simulations demonstrate that entanglement protection depends critically on the proportion of HF components in the power spectral density of the mixed noise. Our work establishes that enhanced HF components are essential for effective noise-assisted entanglement protection, offering key insights for noise engineering in practical open quantum systems.

Figures (6)

• Figure 1: Schematic diagram of two-level atoms interacting with an optical cavity. The cavity leaks into a vacuum bath. The coupling strengths between each atom and the cavity depends on the positions of the atoms within the electromagnetic field. Random motion of atoms induces stochastic coupling strengths $G_{1}(t)$ and $G_{2}(t)$.
• Figure 2: Quantum entanglement protection induced by the mixture of violet noise ($\xi_{a}$) and O-U noise ($\xi_{b}$). The violet, pink, and blue surfaces indicate the time evolution of concurrence under different mixture of violet and O-U noise. The green surface is presented as a comparison to demonstrate the case without noise.
• Figure 3: PSD for three special cases $\gamma_{\xi}=1$, $\gamma_{\xi}=15$, and $\gamma_{\xi}=90$. The PSD for violet noise ($p=1$), O-U noise ($p=0$), and mixed noise ($p=0.5$) are represented by the purple, pink, and blue curves. The black dashed line serves as a phenomenological, approximate boundary to delineate the LF and HF regimes, reflecting a heuristic distinction rather than a rigid, physically inherent threshold.
• Figure 4: Quantum entanglement protection induced by the mixture of telegraph noise ($\xi_{a}$) and O-U noise ($\xi_{b}$). The gray surface corresponds to telegraph noise only, the pink surface corresponds to O-U noise only, and the blue surface represents the mixed noise. As a comparison, the light-green surface shows the case without classical noise. The parameters are $p_{{\rm jump}}=0.35$ (for $\xi_{a}$), $\gamma_{\xi}=15$ (for $\xi_{b}$).
• Figure 5: The PSD of three types of noise are shown in (a), (b), and (c), each corresponding to different values of $\gamma_{{\rm Q}}$ selected in Fig. \ref{['fig:4']}. The gray, pink, and blue curves represent telegraph noise, O-U noise, and mixed noise, respectively. The black dashed line is a hypothetical boundary to distinguish LF and HF domains. Since $\gamma_{{\rm Q}}$ are different in (a), (b), and (c), the reference dashed lines are also moved. This is different from Fig. \ref{['fig:3']}.