A Maxwell's demon type "information engine" that extracts work from a bath is constructed from a microscopic Hamiltonian for the whole system including a subsystem, a thermal bath, and a nonequilibrium bath of phonons or photons that represents an information source or sink. The kinetics of the engine is calculated self-consistently from the state of the nonequilibrium bath, and the relation of this kinetics to the underlying microscopic thermodynamics is established.

• Received 23 May 1994

DOI:https://doi.org/10.1103/PhysRevLett.74.10