  A new method is presented which allows time averaged density matrices of
closed quantum systems to be computed via a constraint overlap maximization.
Due to its simplicity, this method can be combined with algorithms based on
tensor networks, as, e.g., matrix product operators (MPO). An algorithm is
explained and several results for non-integrable Ising chains are given. Among
them are scaling examples, time averaged expectation values, their variances
and operator space entanglement entropies.
