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On the undecidability of quantum channel capacities

arXiv Quantum Physics
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⚡ Quantum Brief
Researchers Bhattacharyya, Mehta, and Zhao proved in January 2026 that computing quantum channel capacities is fundamentally harder than classical channels, marking a breakthrough in quantum information theory. The study demonstrates that calculating a general quantum channel’s capacity is QMA-hard, meaning no efficient quantum algorithm can solve it—a stronger complexity barrier than previously suspected. They also proved the maximal-entanglement-assisted zero-error one-shot classical capacity is uncomputable, resolving a long-standing question about quantum communication limits. This work formalizes earlier suspicions that quantum capacities defy algorithmic computation, contrasting sharply with classical channels where capacities are computable. The findings bridge quantum physics, computational complexity, and information theory, with implications for quantum error correction and network design.
On the undecidability of quantum channel capacities

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Quantum Physics arXiv:2601.22471 (quant-ph) [Submitted on 30 Jan 2026] Title:On the undecidability of quantum channel capacities Authors:Archishna Bhattacharyya, Arthur Mehta, Yuming Zhao View a PDF of the paper titled On the undecidability of quantum channel capacities, by Archishna Bhattacharyya and 2 other authors View PDF HTML (experimental) Abstract:An important distinction in our understanding of capacities of classical versus quantum channels is marked by the following question: is there an algorithm which can compute (or even efficiently compute) the capacity? While there is overwhelming evidence suggesting that quantum channel capacities may be uncomputable, a formal proof of any such statement is elusive. We initiate the study of the hardness of computing quantum channel capacities. We show that, for a general quantum channel, it is QMA-hard to compute its quantum capacity, and that the maximal-entanglement-assisted zero-error one-shot classical capacity is uncomputable. Comments: Subjects: Quantum Physics (quant-ph); Computational Complexity (cs.CC); Information Theory (cs.IT) Cite as: arXiv:2601.22471 [quant-ph] (or arXiv:2601.22471v1 [quant-ph] for this version) https://doi.org/10.48550/arXiv.2601.22471 Focus to learn more arXiv-issued DOI via DataCite (pending registration) Submission history From: Archishna Bhattacharyya [view email] [v1] Fri, 30 Jan 2026 02:35:01 UTC (48 KB) Full-text links: Access Paper: View a PDF of the paper titled On the undecidability of quantum channel capacities, by Archishna Bhattacharyya and 2 other authorsView PDFHTML (experimental)TeX Source view license Current browse context: quant-ph new | recent | 2026-01 Change to browse by: cs cs.CC cs.IT math math.IT 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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Source: arXiv Quantum Physics