Non-abelian anyons on graphs from presentations of graph braid groups

TL;DR

This paper develops algorithms and frameworks for understanding non-abelian anyons on graphs by analyzing graph braid groups, their presentations, and associated unitary representations, with implications for topological quantum computation.

Contribution

It introduces a method to derive physical presentations of graph braid groups from minimal Morse presentations and explores the structure of their unitary representations via moduli spaces.

Findings

Stabilization of moduli spaces for large particle numbers on 2-connected graphs

Framework for studying non-abelian topological phases on graphs

Algorithmic approach to construct physical presentations of graph braid groups

Abstract

The aim of this paper is to analyse algorithms for constructing presentations of graph braid groups from the point of view of anyonic quantum statistics on graphs. In the first part of this paper, we provide a comprehensive review of an algorithm for constructing so-called minimal Morse presentations of graph braid groups that relies on discrete Morse theory. Next, we introduce the notion of a physical presentation of a graph braid group as a presentation whose generators have a direct interpretation as particle exchanges. We show how to derive a physical presentation of a graph braid group from its minimal Morse presentation. In the second part of the paper, we study unitary representations of graph braid groups that are constructed from their presentations. We point out that algebraic objects called moduli spaces of flat bundles encode all unitary representations of graph braid groups. For $2$-connected graphs, we conclude the stabilisation of moduli spaces of flat bundles over graph configuration spaces for large numbers of particles. Moreover, we set out a framework for studying locally abelian anyons on graphs whose non-abelian properties are only encoded in non-abelian topological phases assigned to cycles of the considered graph.