Thinking carefully about quantum information

Abstract

The development of quantum information theory over the last 20 years has produced a plethora of interesting new results and along with them a host of claims have been made by physicists and philosophers about how quantum information theory helps us understand the quantum world. When one examines such claims with any attention to detail, it is quite obvious that radically different and incompatible claims are being made about the quantum world. Christopher Timpson’s Quantum Information Theory and the Foundations of Quantum Mechanics provide a sober and thorough critical guide to these claims. Claims made about how quantum information theory can help us understand the quantum world are a motley collection, and so too are the chapters of Timpson’s book. That said, they can almost be sorted into two broad categories: those that aim to define quantum information and to understand the quantum world in terms of it, and those that aim to reconstruct quantum mechanics in terms of informationtheoretic axioms which will render the quantum world understandable to us. Timpson’s Chapter 6, on quantum computation is the exception. Oftentimes, different concepts of information are deployed in the literature associated with quantum information theory that are as much related as Michael Jackson the pop music icon and Michael Jackson the beer and whisky expert. It is strikingly ironic how much confusion has been generated by appeal to concepts of information. Timpson’s second chapter, ‘‘What is information?’’, is the antidote to such confusion. Timpson claims that there are really only two proper ways to talk about information in this context: the everyday way, which has a strong connection to knowledge, and the technical way, whose roots lie in Shannon (1948). With respect to both, Timpson’s most pressing point is to guard against a view that