Mikhael T. Semann and James P. Crutchfield
ABSTRACT: The averaged steady-state surprisal links a driven stochastic system's information processing to its nonequilibrium thermodynamic response. By explicitly accounting for the effects of nonequilibrium steady states, a decomposition of the surprisal results in an information processing First Law that extends and tightens—to strict equalities—various information processing Second Laws. Applying stochastic thermodynamics' integral fluctuation theorems then shows that the decomposition reduces to the second laws under appropriate limits. In unifying them, the First Law paves the way to identifying the mechanisms by which nonequilibrium steady-state systems extract work from information-bearing degrees of freedom. To illustrate, we analyze an autonomous Maxwellian information ratchet that tunably violates detailed balance in its effective dynamics. This demonstrates how the presence of nonequilibrium steady states qualitatively alters an information engine's allowed functionality.