Quantum

Fidelity Dynamics of a Jaynes--Cummings Qubit under Markovian and Non-Markovian Coupling Noise

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Briefings

This article analyzes the fidelity decay of a Jaynes-Cummings qubit coupled to a cavity under stochastic coupling noise. The study derives exact analytical expressions for noise-averaged density matrices and fidelity relative to ideal evolution. Key findings include a single decoherence factor determined by the integrated noise correlation function, with exponential decay in the white-noise limit and nonexponential decay in the presence of finite correlation times. The research establishes a direct link between microscopic coupling fluctuations and macroscopic coherence loss, providing a unified framework for evaluating cavity-QED protocol robustness.

Key points

• The fidelity of a Jaynes-Cummings qubit coupled to a cavity decays exponentially in the white-noise limit, whereas finite noise correlation times produce nonexponential decay.
• Decoherence increases with photon number due to enhanced effective qubit-cavity coupling, governed by the integrated noise correlation function.

Context

This research addresses stochastic fluctuations in cavity-QED platforms, which are critical for quantum communication, sensing, and information processing. Understanding how coupling noise affects fidelity is essential for assessing protocol robustness.

Limitations

The study relies on analytical derivations within the Jaynes-Cummings model. Results are limited to Gaussian white noise and Ornstein-Uhlenbeck noise models. The analysis does not account for specific fabrication imperfections or environmental disturbances beyond the modeled stochastic fluctuations.

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