Quantum systems equilibrate rapidly for most observables.

@article{Malabarba2014QuantumSE,
  title={Quantum systems equilibrate rapidly for most observables.},
  author={Artur S. L. Malabarba and Luis Pedro Garc{\'i}a-Pintos and Noah Linden and Terence C. Farrelly and Anthony J. Short},
  journal={Physical review. E, Statistical, nonlinear, and soft matter physics},
  year={2014},
  volume={90 1},
  pages={012121}
}
Considering any Hamiltonian, any initial state, and measurements with a small number of possible outcomes compared to the dimension, we show that most measurements are already equilibrated. To investigate nontrivial equilibration, we therefore consider a restricted set of measurements. When the initial state is spread over many energy levels, and we consider the set of observables for which this state is an eigenstate, most observables are initially out of equilibrium yet equilibrate rapidly… CONTINUE READING