The Quantum Realization Functor and the κ-Obstruction Theorem: Why Quantum Computation is Bounded by the Algebraic Geometry of Motives

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Autor principal: Eltgroth, Matthew
Formato: Recurso digital
Lenguaje:inglés
Publicado: Zenodo 2026
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author Eltgroth, Matthew
author_facet Eltgroth, Matthew
contents <p>We introduce the quantum realization procedure H_{\mathrm{QFT}}, which packages the Betti and étale realizations of a motive into a single Hilbert space and implements a computational analogue of the comparison isomorphism at polynomial cost via the quantum Fourier transform.</p> <p>The central result is the κ-obstruction theorem, a purely categorical statement: any exact functor from an abelian category to a semisimple target category annihilates all higher extension groups \mathrm{Ext}^n for n \geq 1. This applies in particular to quantum computation, where measurement maps quantum states to classical outputs in a semisimple category (finite-dimensional vector spaces).</p> <p>We show that the complementarity index \kappa of the Algorithmic Motives (AM) framework corresponds canonically to a nontrivial extension class arising from the derived inverse limit \varprojlim^1, which embeds into \mathrm{Ext}^1 of the motivic category. When \kappa = 0, the obstruction is fully captured by morphisms and can be resolved via the comparison isomorphism, yielding polynomial-time quantum algorithms (e.g., Shor, Biasse–Song). When \kappa > 0, the residual obstruction lies in \mathrm{Ext}^1, which is annihilated by any realization functor and therefore cannot be accessed by any computational model whose output lands in a semisimple category.</p> <p>This establishes a structural limitation on quantum computation: quantum speedup is possible precisely when the relevant motivic obstruction is visible at the level of realizations, and impossible when it resides in extension data invisible to all such functors.</p> <p>The result is independent of physical assumptions and depends only on standard homological algebra and the semisimplicity of the output category.</p>
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spellingShingle The Quantum Realization Functor and the κ-Obstruction Theorem: Why Quantum Computation is Bounded by the Algebraic Geometry of Motives
Eltgroth, Matthew
Quantum computation; motives; Tannakian categories; Ext groups; homological algebra; quantum Fourier transform; complexity theory; arithmetic geometry; Nori motives; category theory
<p>We introduce the quantum realization procedure H_{\mathrm{QFT}}, which packages the Betti and étale realizations of a motive into a single Hilbert space and implements a computational analogue of the comparison isomorphism at polynomial cost via the quantum Fourier transform.</p> <p>The central result is the κ-obstruction theorem, a purely categorical statement: any exact functor from an abelian category to a semisimple target category annihilates all higher extension groups \mathrm{Ext}^n for n \geq 1. This applies in particular to quantum computation, where measurement maps quantum states to classical outputs in a semisimple category (finite-dimensional vector spaces).</p> <p>We show that the complementarity index \kappa of the Algorithmic Motives (AM) framework corresponds canonically to a nontrivial extension class arising from the derived inverse limit \varprojlim^1, which embeds into \mathrm{Ext}^1 of the motivic category. When \kappa = 0, the obstruction is fully captured by morphisms and can be resolved via the comparison isomorphism, yielding polynomial-time quantum algorithms (e.g., Shor, Biasse–Song). When \kappa > 0, the residual obstruction lies in \mathrm{Ext}^1, which is annihilated by any realization functor and therefore cannot be accessed by any computational model whose output lands in a semisimple category.</p> <p>This establishes a structural limitation on quantum computation: quantum speedup is possible precisely when the relevant motivic obstruction is visible at the level of realizations, and impossible when it resides in extension data invisible to all such functors.</p> <p>The result is independent of physical assumptions and depends only on standard homological algebra and the semisimplicity of the output category.</p>
title The Quantum Realization Functor and the κ-Obstruction Theorem: Why Quantum Computation is Bounded by the Algebraic Geometry of Motives
topic Quantum computation; motives; Tannakian categories; Ext groups; homological algebra; quantum Fourier transform; complexity theory; arithmetic geometry; Nori motives; category theory
url https://doi.org/10.5281/zenodo.19273083