Finite-frequency fluctuation-response bounds for open quantum systems

Abstract:We derive a finite-frequency fluctuation-response inequality for Markovian open quantum systems in an input-output setting. For any downstream measurement of the emitted field, the measured lock-in response-to-noise matrix is bounded by the output-field quantum Fisher information rate. For dissipative amplitude modulation with vacuum inputs, this information rate is further bounded by a frequency-independent signal-channel activity, which reduces for kinetic modulation to the stationary channel fluxes. The result is detector-facing but unraveling-independent: it applies after choosing a measurement record, while the information ceiling is set by the quantum field before any detection scheme or trajectory representation is selected. We formulate the bound for multiple signal channels and real finite-frequency quadratures, and illustrate it with a single-sided cavity, resonance fluorescence, and a truncated Kerr-parametric cat resonator.

21 pages, 2 figures. Close to published version

Quantum Physics (quant-ph); Statistical Mechanics (cond-mat.stat-mech)

arXiv:2605.03340 [quant-ph]

(or arXiv:2605.03340v2 [quant-ph] for this version)

https://doi.org/10.48550/arXiv.2605.03340 Focus to learn more arXiv-issued DOI via DataCite

https://doi.org/10.1088/2058-9565/aeaf7f Focus to learn more DOI(s) linking to related resources

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