Information Thermodynamics: a True Exorcism of Maxwell

There have been long-time eorts for about 140 years to resolve the paradox of Maxwells demon since introducted in his 1871 book, Theory of Heat. It opened the era of information thermody- namics where information is transferred as a form of entropy, which was founded much earlier than Shannons idea in computer science. A satisfactory exorcism of demon has been left until the recent theory of feedback control developed late in 2000s and improved up to date. I explain the most recent theory of feedback control and revisit the Szilard engine, one of the most famous and tractable model of Maxwells demon, to demonstrate how a true exorcism can be executed so that the second law thermodynamics is satised without paradox.