Ex(e/o)rcising Demons: Brownian Motors at Work on the Nanoscale

19.1.2009: Prof. Dr. Peter Hänggi (Institut für Physik, Univ. Augsburg): Noise is usually thought of as the enemy of order rather than of a constructive influence. For the phenomena of Brownian motors, however, noise can play a beneficial role in enhancing and facilitating directed transport in absence of biasing forces. We identify variety of intriguing beneficial applications in physical, technological, and biomedical contexts. In their modus operandi such classical and quantum Brownian motors use the energy from the haphazard source of thermal noise in order to perform work against external loads. The basic principles that underpin directed transport in quantum optical and solid-state based devices are elucidated for various nonlinear systems. The very presence of non-equilibrium disturbances enables a Brownian motor to overcome the limiting laws imposed by thermal equilibrium, thereby rectifying quantum Brownian motion for shuttling efficiently quantum objects along a priori designed routes.