  A real-time path integral Monte Carlo approach is developed to study the
dynamics in a many-body quantum system until reaching a nonequilibrium
stationary state. The approach is based on augmenting an exact reduced equation
for the evolution of the system in the interaction picture which is amenable to
an efficient path integral (worldline) Monte Carlo approach. Results obtained
for a model of inelastic tunneling spectroscopy reveal the applicability of the
approach to a wide range of physically important regimes, including high
(classical) and low (quantum) temperatures, and weak (perturbative) and strong
electron-phonon couplings.
