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Simple slow operators and quantum thermalization

arXiv Quantum Physics
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⚡ Quantum Brief
Yang, Gopalakrishnan, and Abanin (April 2026) establish a rigorous link between quantum thermalization and operator dynamics, introducing "simple slow operators" (SSOs) as key indicators of non-thermalizing systems. SSOs are defined as local operators with small Hamiltonian commutators and significant small-sized components, acting as quasi-conserved quantities when thermalization fails on timescale t. The study proves that if typical low-complexity states don’t thermalize by time t, SSOs must exist that remain approximately conserved until t—conversely, their absence guarantees thermalization. A new "ensemble variance norm" quantifies operator expectation values across state ensembles, revealing that for low-entanglement systems, this norm directly ties operator size growth to thermalization behavior. This framework bridges operator dynamics and thermalization, offering a measurable criterion to distinguish thermalizing from non-thermalizing quantum systems without full spectral analysis.
Simple slow operators and quantum thermalization

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Quantum Physics arXiv:2604.13172 (quant-ph) [Submitted on 14 Apr 2026] Title:Simple slow operators and quantum thermalization Authors:Tian-Hua Yang, Sarang Gopalakrishnan, Dmitry A. Abanin View a PDF of the paper titled Simple slow operators and quantum thermalization, by Tian-Hua Yang and 2 other authors View PDF HTML (experimental) Abstract:We establish a rigorous relation between the thermalization of typical initial states and the dynamics of local operators. We introduce a concept of simple slow operators (SSOs), defined as operators that have a small commutator with the Hamiltonian and have significant small-sized components. We show that if typical initial states (drawn from a low-complexity state ensemble) do not thermalize on timescale $t$, then SSOs must exist that are approximately conserved up to timescale $t$. Equivalently, the absence of SSOs implies that typical initial states thermalize. We establish these results by introducing the concept of an ensemble variance norm of an operator, defined as the typical magnitude of the expectation value of that operator with respect to states in the ensemble. For low-entanglement ensembles, the norm is related to operator sizes, allowing us to establish a direct link between operator growth and thermalization. Subjects: Quantum Physics (quant-ph); Statistical Mechanics (cond-mat.stat-mech) Cite as: arXiv:2604.13172 [quant-ph] (or arXiv:2604.13172v1 [quant-ph] for this version) https://doi.org/10.48550/arXiv.2604.13172 Focus to learn more arXiv-issued DOI via DataCite (pending registration) Submission history From: Tian-Hua Yang [view email] [v1] Tue, 14 Apr 2026 18:00:08 UTC (768 KB) Full-text links: Access Paper: View a PDF of the paper titled Simple slow operators and quantum thermalization, by Tian-Hua Yang and 2 other authorsView PDFHTML (experimental)TeX Source view license Current browse context: quant-ph new | recent | 2026-04 Change to browse by: cond-mat cond-mat.stat-mech References & Citations INSPIRE HEP NASA ADSGoogle Scholar Semantic Scholar export BibTeX citation Loading... BibTeX formatted citation × loading... Data provided by: Bookmark Bibliographic Tools Bibliographic and Citation Tools Bibliographic Explorer Toggle Bibliographic Explorer (What is the Explorer?) Connected Papers Toggle Connected Papers (What is Connected Papers?) Litmaps Toggle Litmaps (What is Litmaps?) scite.ai Toggle scite Smart Citations (What are Smart Citations?) Code, Data, Media Code, Data and Media Associated with this Article alphaXiv Toggle alphaXiv (What is alphaXiv?) Links to Code Toggle CatalyzeX Code Finder for Papers (What is CatalyzeX?) DagsHub Toggle DagsHub (What is DagsHub?) GotitPub Toggle Gotit.pub (What is GotitPub?) Huggingface Toggle Hugging Face (What is Huggingface?) ScienceCast Toggle ScienceCast (What is ScienceCast?) Demos Demos Replicate Toggle Replicate (What is Replicate?) Spaces Toggle Hugging Face Spaces (What is Spaces?) Spaces Toggle TXYZ.AI (What is TXYZ.AI?) Related Papers Recommenders and Search Tools Link to Influence Flower Influence Flower (What are Influence Flowers?) Core recommender toggle CORE Recommender (What is CORE?) Author Venue Institution Topic About arXivLabs arXivLabs: experimental projects with community collaborators arXivLabs is a framework that allows collaborators to develop and share new arXiv features directly on our website. Both individuals and organizations that work with arXivLabs have embraced and accepted our values of openness, community, excellence, and user data privacy. arXiv is committed to these values and only works with partners that adhere to them. Have an idea for a project that will add value for arXiv's community? Learn more about arXivLabs. Which authors of this paper are endorsers? | Disable MathJax (What is MathJax?)

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Source: arXiv Quantum Physics