Those interested in thermodynamics may find the following worthwhile: Some recent papers showing that Maxwell's demon may not require energy -
"Single-reservoir heat engine: Controlling the spin" http://fqmt.fzu.cz/13/pdfabstracts/605_1f.pdf "Beyond Landauer Erasure" http://www.mdpi.com/1099-4300/15/11/4956 The latter is part of the journal 'Entropy' - Special Issue "Maxwells Demon 2013" http://www.mdpi.com/journal/entropy/special_issues/maxwells_demon2013 The following paper shows that computation needs no energy - if reversible. "The Connection between Reversibility and Heat Generation" http://people.ccmr.cornell.edu/~clh/p562/TPH/Bohn_TP.pdf Whether a spin (or other conserved quantity) reservoir can be created (or discovered) for less than the thermodynamic energy it returns in a novel engine is an intriguing question - and, also whether such engines can be scaled to macroscopic size. -- Lou Pagnucco
