Witnessing quantum entanglement in solid state systems with neutron scattering

Abstract: Quantum materials promise new states of matter and platforms for next-generation electronics, but in many cases no tractable theoretical models exist for their behavior. Compounding this difficulty is the fact that their key properties—quantum entanglement—have been historically very difficult to probe. In this talk I discuss recent work to use neutron spectroscopy to probe many-body entanglement between electron spins in real solid state materials. By processing neutron scattering data with entanglement witnesses, we are able to experimentally measure Quantum Fisher Information which puts experimental bounds on entanglement depth, and also define a quantum correlation length which can be probed at finite temperatures. We have demonstrated these methods for 1D and 2D quantum spin systems. Our hope is that these tools—which apply to any momentum-resolved probe of dynamic susceptibility—will shed light on the fundamental quantum properties of quantum materials where theoretical models are not forthcoming.