Density Classification with Non-Unitary Quantum Cellular Automata

The density classification (DC) task, a computation which maps global density information to local density, is studied using one-dimensional non-unitary quantum cellular automata (QCAs). Two approaches are considered: one that preserves the number density and one that performs majority voting. For n...

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Main Authors: Elisabeth Wagner, Federico Dell’Anna, Ramil Nigmatullin, Gavin K. Brennen
Format: Article
Language:English
Published: MDPI AG 2024-12-01
Series:Entropy
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Online Access:https://www.mdpi.com/1099-4300/27/1/26
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author Elisabeth Wagner
Federico Dell’Anna
Ramil Nigmatullin
Gavin K. Brennen
author_facet Elisabeth Wagner
Federico Dell’Anna
Ramil Nigmatullin
Gavin K. Brennen
author_sort Elisabeth Wagner
collection DOAJ
description The density classification (DC) task, a computation which maps global density information to local density, is studied using one-dimensional non-unitary quantum cellular automata (QCAs). Two approaches are considered: one that preserves the number density and one that performs majority voting. For number-preserving DC, two QCAs are introduced that reach the fixed-point solution in a time scaling quadratically with the system size. One of the QCAs is based on a known classical probabilistic cellular automaton which has been studied in the context of DC. The second is a new quantum model that is designed to demonstrate additional quantum features and is restricted to only two-body interactions. Both can be generated by continuous-time Lindblad dynamics. A third QCA is a hybrid rule defined by both discrete-time and continuous-time three-body interactions that is shown to solve the majority voting problem within a time that scales linearly with the system size.
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series Entropy
spelling doaj-art-fbdd7c7a13894db9b1a385fd9c77cf5c2025-01-24T13:31:43ZengMDPI AGEntropy1099-43002024-12-012712610.3390/e27010026Density Classification with Non-Unitary Quantum Cellular AutomataElisabeth Wagner0Federico Dell’Anna1Ramil Nigmatullin2Gavin K. Brennen3School of Mathematical and Physical Sciences, Macquarie University, Sydney, NSW 2109, AustraliaDipartimento di Fisica e Astronomia, Università di Bologna, I-40127 Bologna, ItalySchool of Mathematical and Physical Sciences, Macquarie University, Sydney, NSW 2109, AustraliaSchool of Mathematical and Physical Sciences, Macquarie University, Sydney, NSW 2109, AustraliaThe density classification (DC) task, a computation which maps global density information to local density, is studied using one-dimensional non-unitary quantum cellular automata (QCAs). Two approaches are considered: one that preserves the number density and one that performs majority voting. For number-preserving DC, two QCAs are introduced that reach the fixed-point solution in a time scaling quadratically with the system size. One of the QCAs is based on a known classical probabilistic cellular automaton which has been studied in the context of DC. The second is a new quantum model that is designed to demonstrate additional quantum features and is restricted to only two-body interactions. Both can be generated by continuous-time Lindblad dynamics. A third QCA is a hybrid rule defined by both discrete-time and continuous-time three-body interactions that is shown to solve the majority voting problem within a time that scales linearly with the system size.https://www.mdpi.com/1099-4300/27/1/26quantum cellular automatadensity classificationmajority problemquantum computingquantum simulationopen quantum systems
spellingShingle Elisabeth Wagner
Federico Dell’Anna
Ramil Nigmatullin
Gavin K. Brennen
Density Classification with Non-Unitary Quantum Cellular Automata
Entropy
quantum cellular automata
density classification
majority problem
quantum computing
quantum simulation
open quantum systems
title Density Classification with Non-Unitary Quantum Cellular Automata
title_full Density Classification with Non-Unitary Quantum Cellular Automata
title_fullStr Density Classification with Non-Unitary Quantum Cellular Automata
title_full_unstemmed Density Classification with Non-Unitary Quantum Cellular Automata
title_short Density Classification with Non-Unitary Quantum Cellular Automata
title_sort density classification with non unitary quantum cellular automata
topic quantum cellular automata
density classification
majority problem
quantum computing
quantum simulation
open quantum systems
url https://www.mdpi.com/1099-4300/27/1/26
work_keys_str_mv AT elisabethwagner densityclassificationwithnonunitaryquantumcellularautomata
AT federicodellanna densityclassificationwithnonunitaryquantumcellularautomata
AT ramilnigmatullin densityclassificationwithnonunitaryquantumcellularautomata
AT gavinkbrennen densityclassificationwithnonunitaryquantumcellularautomata