The Necessity of Eigenstate Thermalization

Giacomo De Palma, Alessio Serafini, Vittorio Giovannetti, Marcus Cramer

Published 2015-06-24Version 1

Under the eigenstate thermalization hypothesis (ETH), quantum-quenched systems equilibrate towards canonical, thermal ensembles. While at first glance the ETH might seem a very strong hypothesis, we show that it is indeed not only sufficient but also necessary for thermalization. More specifically, we consider systems coupled to baths with well-defined macroscopic temperature and show that whenever all product states thermalize then the ETH must hold.