  We present a history-dependent Monte Carlo scheme for the efficient
calculation of the free-energy of quantum systems, inspired by the Wang-Landau
sampling and metadynamics method. When embedded in a path integral formulation,
it is of general applicability to a large variety of Hamiltonians. In the
two-dimensional quantum Ising model, chosen here for illustration, the accuracy
of free energy, critical temperature, and specific heat is demonstrated as a
function of simulation time, and successfully compared with the best available
approaches, particularly the Wang-Landau method over two different Monte Carlo
procedures.
