Exploring the Quantum: Atoms, Cavities, and Photons , Serge Haroche and Jean-Michel Raimond , Oxford U. Press, New York, 2006. $89.50 (605 pp.). ISBN 978-0-19-850914-1
In 1952 Erwin Schrödinger wrote in the British Journal of the Philosophy of Science , “We never experiment with just one electron or atom or (small) molecule. In thought-experiments we sometimes assume that we do; this invariably entails ridiculous consequences.” One cannot help but wonder how Schrödinger would react to the fact that single atoms, ions, and photons can now be isolated, manipulated, and detected almost routinely, and with exquisite control.
Those developments are quite astounding when we really think about them. After all, it was not until the beginning of the 20th century that the existence of the atom was definitely established. Until the 1970s researchers could only handle atoms in vast quantities. The origins of single-particle trapping and control are found in the pioneering experiments of Hans Dehmelt and coworkers, who succeeded in 1973 in trapping a single electron, eventually for several months at a time, an achievement that led to a revolution in precision measurements. The story has it that Dehmelt became tired of his teachers and colleagues telling him to “consider a single electron” and then chalking a dot on the blackboard; he decided that he wanted to really see one. I also recall the astonishment of the atomic-physics and quantum-optics community at the first images of fluorescence from a lone barium ion trapped by Peter Toschek and his colleagues. Suddenly, it became clear that the thought experiments dreamt up by Schrödinger, Albert Einstein, and the other fathers of quantum mechanics would now become possible: We would soon see whether those experiments did entail ridiculous consequences.
Exploring the Quantum: Atoms, Cavities, and Photons by Serge Haroche and Jean-Michel Raimond describes much of the remarkable progress that has occurred in the trapping and controlling of single atoms, ions, and photons in the past 30 years. The book covers the new and sometimes surprising directions in which these developments are taking us, particularly in the emerging field of quantum information science. The authors, grand masters at that game, are eminently qualified to write such a book. Haroche is a professor at the Collège de France, and Raimond is a professor at the University of Pierre and Marie Curie and at the University Institute of France. For many years the two have been at the forefront of the field of cavity quantum electrodynamics (QED), in which single photons and atoms are trapped and made to interact in intricate ways so that researchers can test and exploit some of the most puzzling aspects of quantum physics. What Exploring the Quantum shows is that the authors are also grand masters at telling us that story. Their monograph is a gem and a must-read for any student of quantum physics, from advanced undergraduate to expert.
Chapter 2 takes readers through a whirlwind pedagogical review of ideas and concepts. It covers considerable ground, from quantum interference to identical particles, from quantum entanglement to quantum teleportation, and from the quantum–classical boundary to quantum information. The chapter also teaches readers how to recast familiar two-state-system physics in terms of qubits manipulated by quantum gates and to represent that physics by quantum-circuit equivalents that become increasingly useful as the manipulation of atoms and fields becomes more elaborate. The authors' approach is indicative of the progression of quantum optics toward engineering applications and the increased influence of quantum information science on current developments in quantum optics. The old-timers among us optical physicists will be particularly fascinated by Haroche and Raimond's illustration of the quantum-circuit equivalent of a Mach–Zehnder interferometer (page 437).
The next two chapters, 3 and 4, discuss two-state systems, harmonic oscillators, and decoherence. The authors give much emphasis to the Jaynes–Cummings model of a two-state system coupled to a simple harmonic oscillator, and to the system's coupling to the environment. The problem is prominent in the rest of the book and is at the heart of quantum optics. Therefore, the chapters could easily form the basis of a short introductory course in quantum optics for advanced undergraduate or beginning graduate students.
In chapters 5 through 7, Haroche and Raimond guide us through a detailed tour of cavity QED—that area of atomic, molecular, and optical science that deals with the interaction between photons trapped in high-Q resonators (photons in a box) and atoms, mostly the two-state variety. In about 200 pages, the authors take readers through topics ranging from superra-dianceand micromasers, to quantum gates, to multiparticle entanglement, to the life and death of Schrödinger cats. They also give many experimental details that emphasize the difficulty and elegance of the experimental work in the field and confirm the empirical law that the difficulty of an experiment is usually inversely related to the difficulty of the theory.
Not surprisingly, the book strongly reflects the personal interests and expertise of the authors; hence, the discussions of trapped ions, quantum degenerate atomic systems, and the potential applications of those systems in quantum information science are less detailed. Other emerging directions, such as circuit QED, are barely touched upon. Still, the close theoretical connections and comparisons between the various systems are clearly emphasized, and chapters 8 and 9 will certainly be useful as an introduction to students and researchers in those areas of quantum optics.
The authors state in their introduction that the text is intended for advanced undergraduate and graduate students. Although the material covered justifies their claim, the lack of problem sets may prevent the book from becoming a canonical text. Yet students at all levels, including advanced researchers, will certainly learn from it a great deal of exciting, modern physics, which the authors present in a way that builds clear bridges between quantum physics and quantum information science.
One criticism is that the index is not very detailed; it has the impression of having been added as an afterthought. I found it of little help in finding important key words and concepts in the text. But that flaw is essentially the only negative I have about this elegant and beautifully produced book. I have no doubt that Schrödinger would have loved Exploring the Quantum.
