Introduction to the Role of Information in Physics

Abstract

The paradox first proposed by Maxwell and well known under the name of “The Maxwell’s Demon paradox” is discussed starting from the contribution to the issue given by L. Szilard in 1929. The accurate analysis of the paradox shows that, in order to violate the Second Principle, Maxwell’s Devil must perform observations and adapt his own strategy accordingly. Performing observations involves creating information. To save the Second Principle, it is required that the created information should be deleted. The latter operation requires dissipation in the form of heat and the Landauer Principle fixes the minimum amount of heat dissipated by erasing one bit of information. The nonseparability of the observer from the observed constitutes a new epistemological paradigm in which the theory of information, both classical and quantum, ceases to be a purely technical discipline to become a fundamental constituent of the theories of Physics. In this chapter, some elements of classical and quantum information theory are briefly dealt with. Zurek’s theory, which explores the possibility that thermodynamic potentials of thermodynamic systems should contain additive contributions due to the description of the configuration by the observer (algorithmic complexity), is reported as an example.