Energy requirement of control: Comments on Szilard's engine and Maxwell's demon

¹ Department of Electrical and Computer Engineering, Texas A&M University College Station, TX 77843-3128, USA
² Department of Engineering Sciences, The Ångström Laboratory, Uppsala University P. O. Box, 534, SE-75121 Uppsala, Sweden, EU

^a Laszlo.Kish@ece.tamu.edu

Received: 26 February 2012
Accepted: 21 May 2012

Abstract

In mathematical physical analyses of Szilard's engine and Maxwell's demon, a general assumption (explicit or implicit) is that one can neglect the energy needed for relocating the piston in Szilard's engine and for driving the trap door in Maxwell's demon. If this basic assumption is wrong, then the conclusions of a vast literature on the implications of the second law of thermodynamics and of Landauer's erasure theorem are incorrect, too. Our analyses of the fundamental information physical aspects of various types of control within Szilard's engine and Maxwell's demon indicate that the entropy production due to the necessary generation of information yield much greater energy dissipation than the energy Szilard's engine is able to produce even if all sources of dissipation in the rest of these demons (due to measurement, decision, memory, etc.) are neglected.