The Kubo-Thermalization Correspondence
Abstract
Quantum thermalization describes how interacting quantum systems relax toward thermal equilibrium, a central problem in modern physics. Yet most experimental information on many-body systems comes from short-time transition spectroscopy, typically interpreted within Kubo's linear-response framework. These perspectives-long-time equilibration versus short-time response-seem fundamentally disconnected. Here we establish an exact link between them: the \emph{Kubo-Thermalization correspondence}, which connects long-time thermalized magnetization under weak driving to short-time linear-response spectra for a spin coupled to a thermal bath. The correspondence holds even when the steady state differs substantially from the initial state and when each regime is individually difficult to describe theoretically. We experimentally confirm the correspondence using effective spin-1/2 impurities realized with ultracold fermions in two internal states coupled to a Fermi sea. Our results provide a rare exact statement about quantum thermalization and offer a novel route to infer thermalization dynamics from equilibrium response measurements in strongly interacting quantum systems, independent of microscopic details of the system--bath coupling.
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BibTeX
@misc{huang2026kubothermalization,
title = {{The Kubo-Thermalization Correspondence}},
author = {Songtao Huang and Xingyu Li and Jianyi Chen and Alan Tsidilkovski and Gabriel G. T. Assumpção and Pengfei Zhang and Hui Zhai and Nir Navon},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2605.06666},
eprint = {2605.06666},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2605.06666},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - The Kubo-Thermalization Correspondence
AU - Songtao Huang
AU - Xingyu Li
AU - Jianyi Chen
AU - Alan Tsidilkovski
AU - Gabriel G. T. Assumpção
AU - Pengfei Zhang
AU - Hui Zhai
AU - Nir Navon
PY - 2026
DA - 2026/10/26
PB - arXiv
DO - 10.48550/arxiv.2605.06666
UR - https://arxiv.org/abs/2605.06666
AB - Quantum thermalization describes how interacting quantum systems relax toward thermal equilibrium, a central problem in modern physics. Yet most experimental information on many-body systems comes from short-time transition spectroscopy, typically interpreted within Kubo's linear-response framework. These perspectives-long-time equilibration versus short-time response-seem fundamentally disconnected. Here we establish an exact link between them: the \emph{Kubo-Thermalization correspondence}, which connects long-time thermalized magnetization under weak driving to short-time linear-response spectra for a spin coupled to a thermal bath. The correspondence holds even when the steady state differs substantially from the initial state and when each regime is individually difficult to describe theoretically. We experimentally confirm the correspondence using effective spin-1/2 impurities realized with ultracold fermions in two internal states coupled to a Fermi sea. Our results provide a rare exact statement about quantum thermalization and offer a novel route to infer thermalization dynamics from equilibrium response measurements in strongly interacting quantum systems, independent of microscopic details of the system--bath coupling.
ER -