“…( 138) is a mathematically rigorous statement if |ψ is essentially drawn at random from a sufficiently large Hilbert space (Bartsch and Gemmer, 2009;Reimann, 2007). In fact, the idea of using random states |ψ has a long history (Alben et al, 1975;De Raedt and De Vries, 1989;Jaklič and Prelovšek, 1994) and is at the basis of various numerical approaches to the density of states (Hams and De Raedt, 2000), thermodynamic quantities (De Vries and De Raedt, 1993;Shimizu, 2012, 2013;Wietek et al, 2019), equilibrium correlation functions (Elsayed and Fine, 2013;Iitaka and Ebisuzaki, 2003;Rousochatzakis et al, 2019;Steinigeweg et al, 2014aSteinigeweg et al, , 2016b, non-equilibrium processes (Endo et al, 2018;Monnai and Sugita, 2014;Richter et al, 2019c), as well as ETH (Steinigeweg et al, 2014c). In this review, we focus on the case of equilibrium correlation functions.…”