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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…

Quantum Physics · Physics 2022-09-20 M. Freedman , M. B. Hastings

Quantum cellular automata (QCAs) are automorphisms of tensor product algebras that preserve locality, with local quantum circuits as a simple example. We study approximate QCAs, where the locality condition is only satisfied up to a small…

Quantum Physics · Physics 2026-03-10 Daniel Ranard , Michael Walter , Freek Witteveen

We consider Clifford Quantum Cellular Automata (CQCAs) and their time evolution. CQCAs are an especially simple type of Quantum Cellular Automata, yet they show complex asymptotics and can even be a basic ingredient for universal quantum…

Quantum Physics · Physics 2010-02-01 Johannes Gütschow , Sonja Uphoff , Reinhard F. Werner , Zoltán Zimborás

There have been several non-axiomatic approaches taken to define Quantum Cellular Automata (QCA). Partitioned QCA (PQCA) are the most canonical of these non-axiomatic definitions. In this work we first show that any QCA can be put into the…

Quantum Physics · Physics 2010-10-14 Pablo Arrighi , Jonathan Grattage

We consider quantum cellular automata for one-dimensional chains of Fermionic modes and study their implementability as finite depth quantum circuits. Fermionic automata have been classified in terms of an index modulo circuits and the…

Quantum-dot Cellular Automata (QCA) as a nanoscale transistor-less device technology offers distinguishing advantages over the limitations of CMOS circuits. While more than 2 decades of design progress have been achieved with QCA, a…

Emerging Technologies · Computer Science 2018-01-31 Shadi Sheikhfaal

Quantum-dot fabrication and characterization is a well-established technology, which is used in photonics, quantum optics and nanoelectronics. Four quantum-dots placed at the corners of a square form a unit cell, which can hold a bit of…

One can think of some physical evolutions as being the emergent-effective result of a microscopic discrete model. Inspired by classical coarse-graining procedures, we provide a simple procedure to coarse-grain color-blind quantum cellular…

Quantum Physics · Physics 2021-04-07 O. Duranthon , Giuseppe Di Molfetta

This paper introduces a new formalism for quantum cellular automata (QCAs), based on evolving tensor products of qubits using local unitary operators. It subsequently uses this formalism to analyze and validate several conjectures, stemming…

Quantum Physics · Physics 2019-10-03 Ruhi Shah , Jonathan Gorard

We provide a complete classification of Clifford quantum cellular automata (QCAs) on arbitrary metric spaces and any qudits (of prime or composite dimensions) in terms of algebraic L-theory. Building on the delooping formalism of Pedersen…

Mathematical Physics · Physics 2026-03-30 Bowen Yang

We provide algebraic criteria for the unitarity of linear quantum cellular automata, i.e. one dimensional quantum cellular automata. We derive these both by direct combinatorial arguments, and by adding constraints into the model which do…

Quantum Physics · Physics 2017-08-29 Pablo Arrighi

We construct a three-dimensional quantum cellular automaton (QCA), an automorphism of the local operator algebra on a lattice of qubits, which disentangles the ground state of the Walker-Wang three fermion model. We show that if this QCA…

Quantum Physics · Physics 2023-02-15 Jeongwan Haah , Lukasz Fidkowski , Matthew B. Hastings

Quantum cellular automata (QCA) are models of quantum computation of particular interest from the point of view of quantum simulation. Quantum lattice gas automata (QLGA - equivalently partitioned quantum cellular automata) represent an…

Mathematical Physics · Physics 2014-01-16 Asif Shakeel , Peter J. Love

Quantum-dot Cellular Automata (QCA) may offer a viable alternative of traditional transistor-based technology at the nanoscale. When modeling a QCA circuit, the number of degrees of freedom necessary to describe the quantum mechanical state…

Mesoscale and Nanoscale Physics · Physics 2007-05-23 Geza Toth , Craig S. Lent

Discretizing spacetime is often a natural step towards modelling physical systems. For quantum systems, if we also demand a strict bound on the speed of information propagation, we get quantum cellular automata (QCAs). These originally…

Quantum Physics · Physics 2020-12-02 Terry Farrelly

Quantum cellular automata are alternative quantum-computing paradigms to quantum Turing machines and quantum circuits. Their working mechanisms are inherently automated, therefore measurement free, and they act in a translation invariant…

Quantum Physics · Physics 2025-07-28 Thiago L. M. Guedes , Don Winter , Markus Müller

We define quantum cellular automata as infinite quantum lattice systems with discrete time dynamics, such that the time step commutes with lattice translations and has strictly finite propagation speed. In contrast to earlier definitions…

Quantum Physics · Physics 2007-05-23 B. Schumacher , R. F. Werner

We show that quantum cellular automata naturally form the degree-zero part of a coarse homology theory. The recent result of Ji and Yang that the space of QCA forms an Omega-spectrum in the sense of algebraic topology is a direct…

K-Theory and Homology · Mathematics 2026-03-27 Matthias Ludewig

Quantum dot Cellular Automata (QCA) is a novel and potentially attractive technology for implementing computing architectures at the nanoscale. The basic Boolean primitive in QCA is the majority gate. In this paper we present a novel design…

Emerging Technologies · Computer Science 2016-11-15 Mostafa Rahimi Azghadi , O. Kavehie , K. Navi

In the near future the era of Beyond CMOS will start as the scaling of the current CMOS technology will reach the fundamental limit. QCA (Quantum-dot Cellular Automata) is the transistor less computation paradigm and viable candidate for…

Emerging Technologies · Computer Science 2017-11-23 Usha Mehta , Vaishali Dhare