NONADIABATIC QUANTUM BROWNIAN RECTIFIERS

We study both dissipative and nondissipative quantum transport in disc rete Brownian rectifiers being driven by nonthermal noise that is unbi ased on average. In the absence of dissipation the current is always z ero and the ballistic diffusion changes into normal diffusion. The dis sipative quantum dynamics exhibits current (with distinctive reversals ) as a result of the cooperative interplay between dissipative forces and external fluctuations. Considering the nonlinear current response to aperiodic, noisy forces we predict aperiodic quantum stochastic res onance. The nonthermal fluctuations can considerably enhance, as well as suppress, the thermal quantum diffusion.