We have, in the last few years, radically improved our grasp of the quantum world. Not just intellectually, either: our ability to manipulate real quantum systems has grown in equal measure with our understanding of their fundamental behavior. These two shoots - the intellectual and the practical harnessing of the quantum world - have sprung up at a time when a third shoot - information processing - has also been experiencing explosive growth. These three shoots are now becoming intertwined. Twisted together, our understanding of information processing, quantum theory and practical quantum...