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Learning Hamiltonians at Long Times

arXiv Quantum Physics
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⚡ Quantum Brief
Researchers proved that unknown local Hamiltonians in n-qubit systems can be uniquely identified from a single long-time evolution operator, even for arbitrarily large times. The work establishes that the Hamiltonian remains the sole approximately conserved local observable under these conditions. The team demonstrates an efficient recovery method using random product-state inputs and classical shadows, reconstructing the Hamiltonian (up to scale) as the null vector of a data matrix. This approach bypasses traditional short-time evolution requirements. A key mathematical result shows that any normalized local observable orthogonal to the Hamiltonian exhibits a Frobenius norm lower bound of 1/poly(n) when commuted with the time-evolved operator, ensuring distinguishability. The findings imply weak equilibration: infinite-temperature autocorrelations of observables orthogonal to the Hamiltonian decay by at least an inverse-polynomial factor, linking learning theory to thermalization dynamics. The work advances quantum Hamiltonian tomography by eliminating the need for multiple time measurements, offering a scalable framework for characterizing complex quantum systems from minimal experimental data.
Learning Hamiltonians at Long Times

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Quantum Physics arXiv:2606.05690 (quant-ph) [Submitted on 4 Jun 2026] Title:Learning Hamiltonians at Long Times Authors:Constantin Cedillo Vayson de Pradenne, Jordan Cotler, Hsin-Yuan Huang View a PDF of the paper titled Learning Hamiltonians at Long Times, by Constantin Cedillo Vayson de Pradenne and 2 other authors View PDF HTML (experimental) Abstract:We study the problem of learning an unknown $n$-qubit Hamiltonian $H$ from $U = e^{-iHt}$ for a single time $t$, where $t$ may be arbitrarily large. For broad families of local Hamiltonians, we prove that, with high probability over $H$ and $t$, any sum of local observables $A$ that is normalized and orthogonal to $H$ satisfies $\tfrac{1}{2^n}\|[U(t),A]\|_F^2 \geq 1/\text{poly}(n)$. The Hamiltonian is therefore the unique approximately conserved local observable, and we can efficiently recover $H$, up to scale, as the approximate null vector of a data matrix built from random product-state inputs and classical shadows. As a corollary, we obtain a weak equilibration statement: the infinite-temperature autocorrelation of every sum of local observables orthogonal to $H$ decays by at least an inverse-polynomial amount. Comments: Subjects: Quantum Physics (quant-ph) Cite as: arXiv:2606.05690 [quant-ph] (or arXiv:2606.05690v1 [quant-ph] for this version) https://doi.org/10.48550/arXiv.2606.05690 Focus to learn more arXiv-issued DOI via DataCite (pending registration) Submission history From: Constantin Cedillo Vayson De Pradenne [view email] [v1] Thu, 4 Jun 2026 04:16:12 UTC (1,557 KB) Full-text links: Access Paper: View a PDF of the paper titled Learning Hamiltonians at Long Times, by Constantin Cedillo Vayson de Pradenne and 2 other authorsView PDFHTML (experimental)TeX Source view license Current browse context: quant-ph new | recent | 2026-06 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