"What is information?"

Ben Schumacher
Caltech

Abstract

Quantum information theory forces us to reconsider just what we mean by the term "information".  Is there a more general physical idea of information that encompasses both quantum and classical concepts? This talk will try to present such a view.  An information theory is a theory of the reversibility (or approximate reversibility) of state changes under a restricted set of feasible operations. Within quantum mechanics, there can be several distinct reasonable choices for the feasible set, and therefore several inequivalent concepts of "information".  But these different types of information must share certain "categorical" features.

We can also adapt this approach to ask, "What is computation?" From the standpoint of physics, computation must be based on the ability of one dynamical evolution to simulate another.  A few observations on the general idea of simulation will be presented.