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arXiv · 2510.12313

Metrological approach to the emergence of classical objectivity

Anthony Kiely·Diana A. Chisholm·Akram Touil·Sebastian Deffner·Gabriel Landi·Steve Campbell
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Abstract

We present a precise characterization of the onset of classicality that combines the formalism of quantum Darwinism with the tools from quantum metrology. We show that the quantum Fisher information provides a useful metric for assessing the rate at which classical objectivity emerges. Furthermore, our formalism allows us to explore how the choice of measurement impacts the precision with which an observer can determine the state of the system. For a paradigmatic example of the spin-star model, we demonstrate that optimal measurements lead to the emergence of classicality at an exponential rate. Although other measurements necessarily lead to slower emergence, we importantly show that suboptimal measurements can still saturate the Cram\'{e}r-Rao bound. By recasting emergent classicality as an information acquisition protocol, our framework provides a precise operational description of quantum Darwinism.

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Anthony Kiely, Diana A. Chisholm, Akram Touil, Sebastian Deffner, Gabriel Landi, Steve Campbell. 2025-10-14. Metrological approach to the emergence of classical objectivity. https://doi.org/10.1103/hn78-7xx3

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