Quantum expanders and property (T) discrete quantum groups

Fuente: arXiv
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Autores principales: Brannan, Michael, Culf, Eric, Vernooij, Matthijs
Formato: Preprint
Publicado: 2025
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author Brannan, Michael
Culf, Eric
Vernooij, Matthijs
author_facet Brannan, Michael
Culf, Eric
Vernooij, Matthijs
contents Families of expander graphs were first constructed by Margulis from discrete groups with property (T). Within the framework of quantum information theory, several authors have generalised the notion of an expander graph to the setting of quantum channels. In this work, we use discrete quantum groups with property (T) to construct quantum expanders in two ways. The first approach obtains a quantum expander family by constructing the requisite quantum channels directly from finite-dimensional irreducible unitary representations, extending earlier work of Harrow using groups. The second approach directly generalises Margulis' original construction and is based on a quantum analogue of a Schreier graph using the theory of coideals. To obtain examples of quantum expanders, we apply our machinery to discrete quantum groups with property (T) coming from compact bicrossed products.
format Preprint
id arxiv_https___arxiv_org_abs_2502_01974
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Quantum expanders and property (T) discrete quantum groups
Brannan, Michael
Culf, Eric
Vernooij, Matthijs
Operator Algebras
Mathematical Physics
Families of expander graphs were first constructed by Margulis from discrete groups with property (T). Within the framework of quantum information theory, several authors have generalised the notion of an expander graph to the setting of quantum channels. In this work, we use discrete quantum groups with property (T) to construct quantum expanders in two ways. The first approach obtains a quantum expander family by constructing the requisite quantum channels directly from finite-dimensional irreducible unitary representations, extending earlier work of Harrow using groups. The second approach directly generalises Margulis' original construction and is based on a quantum analogue of a Schreier graph using the theory of coideals. To obtain examples of quantum expanders, we apply our machinery to discrete quantum groups with property (T) coming from compact bicrossed products.
title Quantum expanders and property (T) discrete quantum groups
topic Operator Algebras
Mathematical Physics
url https://arxiv.org/abs/2502.01974