Thermodynamics of information processing: A minimal model of an autonomous Maxwell Demon

The thermodynamic implications of information processing have recently received renewed attention, in contexts such as quantum information theory, the synthesis of artificial molecular machines, and feedback control in microscopic systems.  A question at the heart of this field is whether or not the Shannon entropy of a random string of data ought to be treated as a genuine thermodynamic entropy, with consequences for the conversion of heat into work. I will address this issue by describing a model system that operates as an autonomous Maxwell Demon.  This "demon" interacts with a thermal reservoir, a stream of bits, and a mass that can be lifted or lowered.  Its dynamics are modeled with thermodynamically consistent transition rates. The steady-state behavior of the model can be solved exactly, and this solution is used to construct the nonequilibrium phase diagram as a function of the model parameters.  The demon can act either as an engine, converting heat to work (lifting the mass) while writing information to the stream of bits; or as an eraser, using the energy of the falling mass to erase information in the bit stream.  The model offers a simple paradigm for exploring the interplay between heat, work and information in small systems.