Quantum Cellular Automata: The Group, the Space, and the Spectrum

Fuente: arXiv
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Main Authors: Ji, Mattie, Yang, Bowen
Format: Preprint
Published: 2026
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author Ji, Mattie
Yang, Bowen
author_facet Ji, Mattie
Yang, Bowen
contents Over an arbitrary commutative ring $R$, we develop a theory of quantum cellular automata. We then use algebraic K-theory to construct a space $\mathbf{Q}(X)$ of quantum cellular automata (QCA) on a given metric space $X$. In most cases of interest, $π_0 \mathbf{Q}(X)$ classifies QCA up to quantum circuits and stabilization. Notably, the QCA spaces are related by homotopy equivalences $\mathbf{Q}(*) \simeq Ω^n \mathbf{Q}(\mathbb{Z}^n)$ for all $n$, which shows that the classification of QCA on Euclidean lattices is given by an $Ω$-spectrum indexed by the dimension $n$. As a corollary, we also obtain a non-connective delooping of the K-theory of Azumaya $R$-algebras, which may be of independent interest. We also include a section leading to the $Ω$-spectrum for QCA over $C^*$-algebras with unitary circuits.
format Preprint
id arxiv_https___arxiv_org_abs_2602_16572
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Quantum Cellular Automata: The Group, the Space, and the Spectrum
Ji, Mattie
Yang, Bowen
Algebraic Topology
Mathematical Physics
Operator Algebras
Rings and Algebras
Quantum Physics
Primary: 19D23, 81P45. Secondary: 55P47
Over an arbitrary commutative ring $R$, we develop a theory of quantum cellular automata. We then use algebraic K-theory to construct a space $\mathbf{Q}(X)$ of quantum cellular automata (QCA) on a given metric space $X$. In most cases of interest, $π_0 \mathbf{Q}(X)$ classifies QCA up to quantum circuits and stabilization. Notably, the QCA spaces are related by homotopy equivalences $\mathbf{Q}(*) \simeq Ω^n \mathbf{Q}(\mathbb{Z}^n)$ for all $n$, which shows that the classification of QCA on Euclidean lattices is given by an $Ω$-spectrum indexed by the dimension $n$. As a corollary, we also obtain a non-connective delooping of the K-theory of Azumaya $R$-algebras, which may be of independent interest. We also include a section leading to the $Ω$-spectrum for QCA over $C^*$-algebras with unitary circuits.
title Quantum Cellular Automata: The Group, the Space, and the Spectrum
topic Algebraic Topology
Mathematical Physics
Operator Algebras
Rings and Algebras
Quantum Physics
Primary: 19D23, 81P45. Secondary: 55P47
url https://arxiv.org/abs/2602.16572