Speaker
Description
Observers, unlike experimentalists, have no control over the autonomously evolving quantum systems they study. They infer dynamics and states from partial observations, limited to spatial subsystems, finite time windows, accessible charges, and finite measurement resolution. This talk will discuss features revealed by analytic and numerical examples of closed systems described as ensembles of their subsystems, with dynamics described by open-system propagators. Restricting to systems with a symmetry, we contrast the statistical properties that emerge from Hamiltonian dynamics and random circuits with constrained circuits that achieve non-equilibrium steady states. These ensembles provide a foundation for better understanding effective theories and inference for observers, especially in out-of-equilibrium systems.