This volume describes a new technology based on harnessing the irreducible uncertainty of the quantum world. Quantum technology manipulates nature at the most elementary level. The first chapter gives the essential principles of quantum mechanical theory using simple geometric arguments. No mathematical knowledge or treatment is assumed. The book then describes various examples of present and future quantum technologies such as schemes to manipulate and trap single atoms with beams of light, quantum nanocircuits and the most powerful computers we can envisage based on quantum theory.