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Trading symmetry for Hilbert-space dimension in Bell-inequality violation

Hsin-Yu Hsu, Gelo Noel M. Tabia, Kai-Siang Chen, Mu-En Liu, Tam\'as V\'ertesi, Nicoals Brunner, Yeong-Cherng Liang
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⚡ Quantum Brief
A January 2026 study by Hsin-Yu Hsu and collaborators examines how symmetry constraints in Bell tests affect quantum advantage, revealing that asymmetry can enable stronger violations of certain Bell inequalities. The team proves that for symmetric Collins-Gisin-Linden-Massar-Popescu inequalities, maximal violation requires neither symmetry trade-offs nor higher-dimensional quantum systems. However, for other Bell inequalities with few dichotomic measurements, symmetric strategies in minimal Hilbert space dimensions yield only suboptimal violations, demanding asymmetric approaches for peak performance. Conversely, some asymmetric Bell inequalities paradoxically achieve maximal violation through symmetric quantum correlations, challenging conventional assumptions about symmetry’s role. The findings reshape understanding of quantum correlation geometry and may advance self-testing protocols by clarifying when symmetry must be sacrificed for optimal Bell violation.
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Quantum Physics arXiv:2601.02893 (quant-ph) [Submitted on 6 Jan 2026] Title:Trading symmetry for Hilbert-space dimension in Bell-inequality violation Authors:Hsin-Yu Hsu, Gelo Noel M. Tabia, Kai-Siang Chen, Mu-En Liu, Tamás Vértesi, Nicoals Brunner, Yeong-Cherng Liang View a PDF of the paper titled Trading symmetry for Hilbert-space dimension in Bell-inequality violation, by Hsin-Yu Hsu and 6 other authors View PDF HTML (experimental) Abstract:In quantum information, asymmetry, i.e., the lack of symmetry, is a resource allowing one to accomplish certain tasks that are otherwise impossible. Similarly, in a Bell test using any given Bell inequality, the maximum violation achievable using quantum strategies respecting or disregarding a certain symmetry can be different. In this work, we focus on the symmetry involved in the exchange of parties and explore when we have to trade this symmetry for a lower-dimensional quantum strategy in achieving the maximal violation of given Bell inequalities. For the family of symmetric Collins-Gisin-Linden-Massar-Popescu inequalities, we provide evidence showing that there is no such trade-off. However, for several other Bell inequalities with a small number of dichotomic measurement settings, we show that symmetric quantum strategies in the minimal Hilbert space dimension can only lead to a suboptimal Bell violation. In other words, there exist symmetric Bell inequalities that can only be maximally violated by asymmetric quantum strategies of minimal dimension. In contrast, one can also find examples of asymmetric Bell inequalities that are maximally violated by symmetric correlations. The implications of these findings on the geometry of the set of quantum correlations and the possibility of performing self-testing therefrom are briefly discussed. Comments: Subjects: Quantum Physics (quant-ph) Cite as: arXiv:2601.02893 [quant-ph] (or arXiv:2601.02893v1 [quant-ph] for this version) https://doi.org/10.48550/arXiv.2601.02893 Focus to learn more arXiv-issued DOI via DataCite (pending registration) Submission history From: Hsin-Yu Hsu [view email] [v1] Tue, 6 Jan 2026 10:27:27 UTC (115 KB) Full-text links: Access Paper: View a PDF of the paper titled Trading symmetry for Hilbert-space dimension in Bell-inequality violation, by Hsin-Yu Hsu and 6 other authorsView PDFHTML (experimental)TeX Source view license Current browse context: quant-ph new | recent | 2026-01 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?) Links to Code Toggle Papers with Code (What is Papers with Code?) 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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