This book adopts a novel, physics-first approach to quantum measurement, using physical experiments as the basis to describe the underlying mathematical formalism. Topics covered include weak measurements, quantum measurement reversal, quantum trajectories and the stochastic path integral formalism. The theory of quantum measurement is also covered in detail, including discussion of how it can be tested and demonstrated in a laboratory: how to build quantum-limited amplifiers, fundamental noise limits imposed on measurement by quantum mechanics, and the design of superconducting circuits. This text is an excellent introduction for students with a basic understanding of quantum mechanics wanting to learn more about measurement theory, and the inclusion of a wide selection of end-of-chapter exercises make this book ideal for emerging courses on the topic. Key chapters introducing the foundations of quantum computing and the history of measurement theory are equally accessible to a broader, less specialised audience.

‘There is a spot in the great John Archibald Wheeler’s autobiography where he writes, ‘Many students entering upon their study of quantum mechanics are told that [the theory] shows its essence in the equation Erwin Schrödinger published in 1926. … But, to my mind, the Schrödinger wave fails to capture the true essence of quantum mechanics. That essence is measurement.’ Were Wheeler but alive today to see this marvelous book! His outlook shaped my own approach to the foundations of quantum theory, but this book is the first living instantiation of Wheeler’s deep thought to physical practice itself. It will be a standard reference for years to come.’

Christopher Fuchs - University of Massachusetts Boston

‘This is a fascinating exploration of quantum measurement, going far beyond the standard textbook coverage and guided by the most recent experiments. Essential reading for quantum physicists and engineers and a valuable reference for all those seeking an in-depth understanding of fundamental quantum processes and solid-state quantum devices.’

Jean-Michel Raimond - Sorbonne Université

‘Theoretical and experimental physicists mean different things when they refer to the quantum measurement problem. In this book two world leading quantum physicists, one a theoretician and one an experimentalist, give a comprehensive treatment of the real measurement problem: how to intervene and control the quantum world. This problem is at the foundation of the rapidly developing quantum technology industry. In so doing, they recast moribund questions in quantum foundations and provide the tools for more effective quantum technology.’

Gerard Milburn - The University of Queensland