Quantum entanglement and quantum geometry measured with inelastic x-ray scattering

The authors experimentally investigate here the quantum geometry and quantum information in the insulator LiF. Using sum rules for the measured density-density response, the authors compute the quantum Fisher information of LiF associated with density perturbations, and from these extrapolate a component of the quantum metric tensor. These results serve as a proof of principle that scattering techniques can quantify state-of-the-art quantum geometric quantities in materials, and establishes the quantum Fisher information as an experimentally accessible generalization of quantum geometry to real materials.