We analyze the operation of a molecular machine driven by the nonadiabatic variation of external parameters. We derive a formula for the integrated flow from one configuration to another, obtain a “no-pumping theorem” for cyclic processes with thermally activated transitions, and show that in the adiabatic limit the pumped current is given by a geometric expression.

• Received 24 July 2008

DOI:https://doi.org/10.1103/PhysRevLett.101.140602