  Ergodicity-breaking and slow relaxation are intriguing aspects of
nonequilibrium dynamics both in classical and in quantum settings. These
phenomena are typically associated with phase transitions, e.g. the emergence
of metastable regimes near a first-order transition or scaling dynamics in the
vicinity of critical points. Despite being of fundamental interest the
associated divergent time scales are a hindrance when trying to explore
steady-state properties. Here we show that the relaxation dynamics of Markovian
open quantum systems can be accelerated exponentially by devising an optimal
unitary transformation that is applied to the quantum system immediately before
the actual dynamics. This initial "rotation" is engineered in such a way that
the state of the quantum system becomes orthogonal to the slowest decaying
dynamical mode. We illustrate our idea -- which is inspired by the so-called
Mpemba effect, i.e., water freezing faster when initially heated up -- by
showing how to achieve an exponential speed-up in the convergence to
stationarity in Dicke models, and how to avoid metastable regimes in an
all-to-all interacting spin system.
