Surface Entanglement in Quantum Spin Networks

TL;DR

This paper investigates how boundary spins in quantum spin networks can become strongly entangled over long distances when weakly coupled to the bulk, with implications for quantum communication.

Contribution

It generalizes the phenomenon of long-distance entanglement to arbitrary geometries and discusses how surface entanglement patterns can be controlled.

Findings

Surface spins are strongly entangled when weakly coupled to the bulk.

Entanglement patterns range from bipartite to multipartite depending on couplings.

Results enable quantum routers for distributing quantum correlations.

Abstract

We study the ground-state entanglement in systems of spins forming the boundary of a quantum spin network in arbitrary geometries and dimensionality. We show that as long as they are weakly coupled to the bulk of the network, the surface spins are strongly entangled, even when distant and non directly interacting, thereby generalizing the phenomenon of long-distance entanglement occurring in quantum spin chains. Depending on the structure of the couplings between surface and bulk spins, we discuss in detail how the patterns of surface entanglement can range from multi-pair bipartite to fully multipartite. In the context of quantum information and communication, these results find immediate application to the implementation of quantum routers, that is devices able to distribute quantum correlations on demand among multiple network nodes.