Quantum-Coherent Thermodynamics: Leaf Typicality via Minimum-Variance Foliation

Fuente: arXiv
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Autore principale: Fagotti, Maurizio
Natura: Preprint
Pubblicazione: 2026
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author Fagotti, Maurizio
author_facet Fagotti, Maurizio
contents Equilibrium statistical ensembles commute with the Hamiltonian and thus carry no coherence in the energy eigenbasis. We develop a framework in which energy fluctuations can retain genuinely quantum-coherent contributions. We foliate state space into ``minimum-variance leaves,'' defined by minimizing the average energy variance over all pure-state decompositions, with the minimum set by the quantum Fisher information. On each leaf we construct the least-biased state compatible with normalization and mean energy, defining a leaf-canonical ensemble. The Gibbs ensemble is recovered on the distinguished commuting leaf, while generic states are organized by their leaf label. This structure provides a natural setting to extend eigenstate thermalization beyond equilibrium via a ``leaf typicality'' hypothesis. According to that hypothesis, local observables depend only on the leaf and energy and are reproduced by a representative pure state drawn from the optimal ensemble, whose minimized energy spread reduces the complexity of time evolution.
format Preprint
id arxiv_https___arxiv_org_abs_2602_12212
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Quantum-Coherent Thermodynamics: Leaf Typicality via Minimum-Variance Foliation
Fagotti, Maurizio
Quantum Physics
Statistical Mechanics
Mathematical Physics
Equilibrium statistical ensembles commute with the Hamiltonian and thus carry no coherence in the energy eigenbasis. We develop a framework in which energy fluctuations can retain genuinely quantum-coherent contributions. We foliate state space into ``minimum-variance leaves,'' defined by minimizing the average energy variance over all pure-state decompositions, with the minimum set by the quantum Fisher information. On each leaf we construct the least-biased state compatible with normalization and mean energy, defining a leaf-canonical ensemble. The Gibbs ensemble is recovered on the distinguished commuting leaf, while generic states are organized by their leaf label. This structure provides a natural setting to extend eigenstate thermalization beyond equilibrium via a ``leaf typicality'' hypothesis. According to that hypothesis, local observables depend only on the leaf and energy and are reproduced by a representative pure state drawn from the optimal ensemble, whose minimized energy spread reduces the complexity of time evolution.
title Quantum-Coherent Thermodynamics: Leaf Typicality via Minimum-Variance Foliation
topic Quantum Physics
Statistical Mechanics
Mathematical Physics
url https://arxiv.org/abs/2602.12212