This volume investigates the fundamental physical principles and operational definitions required to classify engineered devices as true quantum machines. The editors, including Michel Devoret and Robert Schoelkopf, compile selected papers from the 100th Les Houches Summer School to establish a rigorous framework for distinguishing between classical devices that utilize quantum effects, such as lasers, and systems where signal variables function as quantum operators.

Experts recognize this collection as a specialized resource for graduate-level researchers and practitioners in quantum information and condensed matter physics. Readers frequently note the high academic density of the prose and the necessity of a strong background in quantum mechanics to fully grasp the technical arguments presented.