Quantum

Open-System Probe Selection and Optimal Measurements for Dispersive Coupling Metrology

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Briefings

This article investigates how photon loss and environmental memory influence probe selection for estimating dispersive coupling strength in cavity qubit systems. Using quantum state diffusion and density operator methods, the study finds that closed system generator variance alone does not determine open system performance. Key findings include that environmental memory can enhance sensitivity and prolong it even when Markovian QFI vanishes, and that separable probes can outperform entangled ones under single photon preparations. The research also identifies a fixed Hermitian observable whose error propagation uncertainty remains near the quantum Cramer Rao bound in the Markovian regime.

Key points

• Environmental memory can enhance and prolong sensitivity in open systems, even when the Markovian quantum Fisher information vanishes.
• Separable probe preparations can outperform entangled probe families for estimating dispersive coupling strength under single photon conditions.

Context and limitations

Results are limited to Markovian and non-Markovian regimes with separable and entangled initial states. Numerical identification of the optimal observable is restricted to the Markovian regime, and specific parameter values are not provided.

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