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Classification of Quantum Cellular Automata

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arxiv 1902.10285 v3 pith:5K5OIAPE submitted 2019-02-27 quant-ph math-phmath.MP

classification quant-phmath-phmath.MP
keywords automataclassificationdimensionscellularindexquantumtheoryhigher
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There exists an index theory to classify strictly local quantum cellular automata in one dimension. We consider two classification questions. First, we study to what extent this index theory can be applied in higher dimensions via dimensional reduction, finding a classification by the first homology group of the manifold modulo torsion. Second, in two dimensions, we show that an extension of this index theory (including torsion) fully classifies quantum cellular automata, at least in the absence of fermionic degrees of freedom. This complete classification in one and two dimensions by index theory is not expected to extend to higher dimensions due to recent evidence of a nontrivial automaton in three dimensions. Finally, we discuss some group theoretical aspects of the classification of quantum cellular automata and consider these automata on higher dimensional real projective spaces.

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Cited by 2 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

  1. Causal Decompositions of 1D Quantum Cellular Automata

    quant-ph 2025-06 conditional novelty 8.0 of 10

    For N > 4r, every 1D quantum cellular automaton of causality radius r is exactly a routed unitary circuit of nearest-neighbour interactions, and translation-invariant automata get translation-invariant circuits.

  2. Anomaly-free symmetries with obstructions to gauging and onsiteability

    cond-mat.str-el 2025-07 conditional novelty 7.0 of 10

    A new class of two-dimensional lattice symmetries is anomaly-free yet obstructs both gauging and on-site realization, with the obstruction classified by H^2(G,Q+).

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