Experimental realisation of multipartite entanglement via quantum Fisher information in a uniform antiferromagnetic quantum spin chain

TL;DR

This paper demonstrates the experimental detection and quantification of multipartite entanglement in a quantum spin chain using quantum Fisher information derived from neutron scattering data, revealing strong entanglement at quantum phase transitions.

Contribution

It provides the first experimental measurement of multipartite entanglement in a bulk solid using quantum Fisher information in a quantum spin chain.

Findings

Quantum Fisher information detects multipartite entanglement.

Entanglement scales indicate a strongly entangled quantum phase transition.

The spin chain belongs to a class with divergent multipartite entanglement.

Abstract

Quantum entanglement is a quantum mechanical phenomenon where the quantum state of a many-body system with many degrees of freedom cannot be described independently of the state of each body with a given degree of freedom, no matter how far apart in space each body is. Entanglement is not only considered a resource in quantum information but also believed to affect complex condensed matter systems. Detecting and quantifying multi-particle entanglement in a many-body system is thus of fundamental significance for both quantum information science and condensed matter physics. Here, we detect and quantify multipartite entanglement in a spin 1/2 Heisenberg antiferromagnetic chain in a bulk solid. Multipartite entanglement was detected using quantum Fisher information which was obtained using dynamic susceptibility measured via inelastic neutron scattering. The scaling behaviour of quantum Fisher information was found to identify the spin 1/2 Heisenberg antiferromagnetic chain to belong to a class of strongly entangled quantum phase transitions with divergent multipartite entanglement.