Robust device-independent characterization of sharpness and incompatibility of unsharp instruments

Quantum Physics arXiv:2608.06726 (quant-ph) [Submitted on 7 Aug 2026] Title:Robust device-independent characterization of sharpness and incompatibility of unsharp instruments Authors:Qian Zhang, Kai-Yu Yuan, Yan-Xin Rong, Zhen Shang, Yong-Jian Gu, Ya Xiao View a PDF of the paper titled Robust device-independent characterization of sharpness and incompatibility of unsharp instruments, by Qian Zhang and 5 other authors View PDF HTML (experimental) Abstract:Unsharp measurements are key resources for tasks that balance information gain and disturbance, but certifying them without device assumptions remains a challenge. We propose a fully device-independent protocol for characterizing unsharp instruments, based on an entanglement-assisted sequential quantum random access code, where the first decoder is allowed to communicate her measurement setting to the second. This communication-enhanced scheme creates a decoding regime in which both decoders surpass classical bounds, enabling tight quantification of sharpness and direct quantification of measurement incompatibility beyond noncommunicating protocols. Experimentally, we implement tunable unsharp measurements using a Mach-Zehnder interferometer, observing the predicted sequential enhancement in decoding probability. Additionally, we achieve significantly narrower sharpness intervals and incompatibility quantification across multiple target sharpness values. Our results show that communication is a powerful operational resource for certifying precisely unsharp instruments and advancing device-independent quantum information protocols. Comments: Subjects: Quantum Physics (quant-ph) Cite as: arXiv:2608.06726 [quant-ph] (or arXiv:2608.06726v1 [quant-ph] for this version) https://doi.org/10.48550/arXiv.2608.06726 Focus to learn more arXiv-issued DOI via DataCite (pending registration) Journal reference: Physical Review A 114, 022411 (2026) Related DOI: https://doi.org/10.1103/yxq6-n2nr Focus to learn more DOI(s) linking to related resources Submission history From: Ya Xiao Dr [view email] [v1] Fri, 7 Aug 2026 02:43:16 UTC (10,524 KB) Full-text links: Access Paper: View a PDF of the paper titled Robust device-independent characterization of sharpness and incompatibility of unsharp instruments, by Qian Zhang and 5 other authorsView PDFHTML (experimental)TeX Source view license Current browse context: quant-ph new | recent | 2026-08 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?)