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

Abstract:We investigate how photon loss and environmental memory affect probe selection and measurement sensitivity for estimating the dispersive coupling strength in a cavity qubit system. Using density operator and quantum state diffusion approaches, we examine the quantum Fisher information for representative separable and entangled initial states in Markovian and non Markovian regimes. The results show that closed system generator variance alone does not determine open system performance. The survival of parameter sensitive coherences and the influence of environmental memory also play important roles. Within the single photon preparations examined, a separable probe can outperform the entangled family considered. Comparisons of selected coherent and squeezed vacuum preparations at equal mean photon number further illustrate how photon number statistics and qubit preparation affect sensitivity. For the parameters studied, finite environmental memory can enhance and prolong sensitivity and yield nonzero QFI for a probe whose Markovian QFI vanishes. We also numerically identify a fixed Hermitian observable whose error propagation uncertainty remains close to the quantum Cramer Rao bound over a prescribed coupling interval in the Markovian regime. These findings clarify the interplay between probe preparation, environmental dynamics, and measurement choice in dispersive quantum metrology.

arXiv:2610.07221 [quant-ph]

(or arXiv:2610.07221v1 [quant-ph] for this version)

https://doi.org/10.48550/arXiv.2610.07221 Focus to learn more arXiv-issued DOI via DataCite (pending registration)

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