Universal delocalization rate in driven dissipative two-level systems at high temperature

We study the lifetime of localized states in a two-level system coupled to a dissipative bath and driven by strong time-periodic monochromatic fields. At high temperature, moderate friction and high frequency driving the dynamics is practically exponential characterized by a rate constant. By mapping the driven dissipative two-level system onto a dissipative multilevel curve-crossing problem and applying semiclassical nonadiabatic rate theory we show that strong fields can stabilize localized states over long time intervals and that the delocalization rate exhibits a ‘‘universal’’ plateau whose value depends only on the intensity of the driving field. Numerical path integral results confirm our theoretical predictions. @S1063-651X~97!06103-5#