Measurement Speed Limits for Quantum State Purification

Quantum Physics arXiv:2607.09118 (quant-ph) [Submitted on 10 Jul 2026] Title:Measurement Speed Limits for Quantum State Purification Authors:Jiaxin Liu, Zuoxian Wang, Danyue Ma View a PDF of the paper titled Measurement Speed Limits for Quantum State Purification, by Jiaxin Liu and 2 other authors View PDF HTML (experimental) Abstract:We derive three matched speed limits on the purification of a monitored system, valid in every finite dimension and for every strategy and efficiency. All three are set by one functional, the square root of the state's impurity, whose maximal decay rate is a state-independent constant. For a qubit this reduces to the square root of the determinant, whose protocol-independent decay at unit efficiency is a sharp null test. The three rate constants stand in ratio two to four to eight, and attainment freezes at that square root, the half-moment. Numerics confirm the bounds; for the qubit, a conservation law settles the local-versus-global optimality puzzle, and doubling feedback spends exactly twice the minimum. Comments: Subjects: Quantum Physics (quant-ph) Cite as: arXiv:2607.09118 [quant-ph] (or arXiv:2607.09118v1 [quant-ph] for this version) https://doi.org/10.48550/arXiv.2607.09118 Focus to learn more arXiv-issued DOI via DataCite (pending registration) Submission history From: Zuoxian Wang [view email] [v1] Fri, 10 Jul 2026 06:16:29 UTC (233 KB) Full-text links: Access Paper: View a PDF of the paper titled Measurement Speed Limits for Quantum State Purification, by Jiaxin Liu and 2 other authorsView PDFHTML (experimental)TeX Source view license Current browse context: quant-ph new | recent | 2026-07 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?)