Langevin simulations of quantum systems

We explore the potential of the Langevin simulation of quantum systems. A generalized quantum sine-Gordon chain, a generalized Toda chain, and impenetrable bosons on a ring are treated specifically to estimate low-lying excitation energies from the long-time behavior of the Langevin process. In the sine-Gordon case, we investigated the dependence of the bound-state frequency on the coupling constant, while in the Toda chain the phonon dispersion curves are obtained for different coupling constants. Finally, for impenetrable bosons the estimated dynamic form factor for density fluctuations is compared with exact results. © 1987 The American Physical Society.