Unitary Quantum Cellular Automata for Density Classification

Fuente: arXiv
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Hauptverfasser: Costa, Pedro C. S., Sanders, Yuval R., Balbi, Pedro Paulo, Brennen, Gavin K.
Format: Preprint
Veröffentlicht: 2025
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author Costa, Pedro C. S.
Sanders, Yuval R.
Balbi, Pedro Paulo
Brennen, Gavin K.
author_facet Costa, Pedro C. S.
Sanders, Yuval R.
Balbi, Pedro Paulo
Brennen, Gavin K.
contents We investigate the density classification task (DCT) -- determining the majority bit in a one-dimensional binary lattice -- within a quantum cellular automaton (CA) framework. While there is no one-dimensional two-state, radius $r \geq 1$, deterministic CA with periodic boundary conditions that solves the DCT perfectly, we explore whether a unitary quantum model can succeed. We employ the Partitioned Unitary Quantum Cellular Automaton (PUQCA), a number-conserving model, and, via evolutionary search, find solutions to the DCT where the success condition is stipulated in terms of measurement probabilities rather than convergence to fixed-point configurations. Finally, we identify a classically simulable regime of the PUQCA in which we find rules that solve the DCT at fixed system sizes and analyze their performance.
format Preprint
id arxiv_https___arxiv_org_abs_2510_06947
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Unitary Quantum Cellular Automata for Density Classification
Costa, Pedro C. S.
Sanders, Yuval R.
Balbi, Pedro Paulo
Brennen, Gavin K.
Quantum Physics
We investigate the density classification task (DCT) -- determining the majority bit in a one-dimensional binary lattice -- within a quantum cellular automaton (CA) framework. While there is no one-dimensional two-state, radius $r \geq 1$, deterministic CA with periodic boundary conditions that solves the DCT perfectly, we explore whether a unitary quantum model can succeed. We employ the Partitioned Unitary Quantum Cellular Automaton (PUQCA), a number-conserving model, and, via evolutionary search, find solutions to the DCT where the success condition is stipulated in terms of measurement probabilities rather than convergence to fixed-point configurations. Finally, we identify a classically simulable regime of the PUQCA in which we find rules that solve the DCT at fixed system sizes and analyze their performance.
title Unitary Quantum Cellular Automata for Density Classification
topic Quantum Physics
url https://arxiv.org/abs/2510.06947