Recent decades of research contributed significantly to our understanding how an interacting quantum system, evolving in isolation from environment, approaches a thermal equilibrium. This process is called thermalization, and the state of the system is referred to as being ergodic. The mechanism of thermalization is today understood via the eigenstate thermalization hypothesis stating that all eigenstates of a Hamiltonian are already thermal, which is a consequence of many-body quantum chaos. Under what conditions can a physical system not thermalize, that is, not be chaotic and cannot be attributed a temperature? This question has been intensively studied in the last decade in many-body quantum systems. The main motivation of these studies is to establish a new type of quantum phase transitions dubbed ergodicity breaking phase transitions. I will describe some of their properties and provide examples of recent studies that may lead to a new understanding of these transitions.
Quantum entanglement, foundations and experiments
Prof. Dr. Anton Zeilinger
Nobel laureate in physics in 2022
University of Vienna, Austrian Academy of Sciences, Austria
