Quantum thermalization in disordered spin systems using fluctuation-dissipation relations

Thermalization in closed, isolated quantum systems is a rather poorly understood topic. The eigenstate thermalization hypothesis (ETH) ensures that the system equilibrates sensibly but it can’t be checked by experiment in a straight-forward manner. However ETH guarantees the existence of Fluctuation-dissipation relations (FDR), relating the system’s thermal fluctuation with how perturbations on the system dissipate. These are experimentally accessible and may offer a measurable indicator for thermalization.