  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.
