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Accelerating Classical and Quantum Tensor PCA

arXiv Quantum Physics
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⚡ Quantum Brief
Matthew B. Hastings proposes quadratic speedups for both classical and quantum tensor PCA algorithms, reducing runtime for detection tasks in "spiked" Gaussian tensors. The quantum version now achieves an eighth-power speedup over the original classical baseline. The modified quantum algorithm further extends its advantage, reaching a sixth-power speedup over the improved classical method—though proofs currently cover only detection, not full tensor recovery. A late-discovered reference (Ref. 3) tightens spectral norm bounds, potentially eliminating provable polynomial speedups. Hastings argues the results may still hold if broader spectral properties (like density of states) remain valid. The work targets high-dimensional linear operators in exponential vector spaces, where quantum approaches previously showed exponential space savings and quartic time advantages. The techniques likely apply to other problems using similar quartic quantum speedups, though validation depends on unproven spectral assumptions. A new section addresses required density-of-states conditions.
Accelerating Classical and Quantum Tensor PCA

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Quantum Physics arXiv:2602.10366 (quant-ph) [Submitted on 10 Feb 2026] Title:Accelerating Classical and Quantum Tensor PCA Authors:Matthew B. Hastings View a PDF of the paper titled Accelerating Classical and Quantum Tensor PCA, by Matthew B. Hastings View PDF HTML (experimental) Abstract:Spectral methods are a leading approach for tensor PCA with a ``spiked" Gaussian tensor. The methods use the spectrum of a linear operator in a vector space with exponentially high dimension and in Ref. 1 it was shown that quantum algorithms could then lead to an exponential space saving as well as a quartic speedup over classical. Here we show how to accelerate both classical and quantum algorithms quadratically, while maintaining the same quartic separation between them. That is, our classical algorithm here is quadratically faster than the original classical algorithm, while the quantum algorithm is eigth-power faster than the original classical algorithm. We then give a further modification of the quantum algorithm, increasing its speedup over the modified classical algorithm to the sixth power. We only prove these speedups for detection, rather than recovery, but we give a strong plausibility argument that our algorithm achieves recovery also. Note added: After this paper was prepared, A. Schmidhuber pointed out to me Ref. 3. This improves the best existing bounds on the spectral norm of a certain random operator. Because the norm of this operator enters into the runtime, with this improvement on the norm, we no longer have a provable polynomial speedup. Our results are phrased in terms of certain properties of the spectrum of this operator (not merely the largest eigenvalue but also the density of states). So, if these properties still hold, the speedup still holds. Rather than modify the paper, I have left it unchanged but added a section at the end discussing the needed property of density of states and considering for which problems (there are several problems for which this kind of quartic quantum speedup has been used and the techniques here will likely be applicable to several of them) the property is likely to hold. Comments: Subjects: Quantum Physics (quant-ph) Cite as: arXiv:2602.10366 [quant-ph] (or arXiv:2602.10366v1 [quant-ph] for this version) https://doi.org/10.48550/arXiv.2602.10366 Focus to learn more arXiv-issued DOI via DataCite (pending registration) Submission history From: Matthew Hastings [view email] [v1] Tue, 10 Feb 2026 23:35:30 UTC (23 KB) Full-text links: Access Paper: View a PDF of the paper titled Accelerating Classical and Quantum Tensor PCA, by Matthew B. HastingsView PDFHTML (experimental)TeX Source view license Current browse context: quant-ph new | recent | 2026-02 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