The physics of forgetting: Landauer's erasure principle and information theory

This article discusses the concept of information and its intimate relation ship with physics. After an introduction of all the necessary quantum mecha nical and information theoretical concepts we analyse Landauer's principle which states that the erasure of information is inevitably accompanied by t he generation of heat. We employ this principle to rederive a number of res ults in classical and quantum information theory whose rigorous mathematica l derivations are difficult. This demonstrates the usefulness of Landauer's principle and provides an introduction to the physical theory of informati on.