This book covers the main ideas, methods, recent developments and applications of quantum-limit optical spectroscopy to quantum information, resolution spectroscopy, measurements beyond quantum limits, measurement of decoherence and entanglement. Quantum-limit spectroscopy lies at the frontier of current experimental and theoretical techniques, and is one of the areas of atomic spectroscopy where the quantization of the field is essential to predict and interpret the existing experimental results. Currently, there is an increasing interest in quantum and precision spectroscopy both theoretically and experimentally, due to a significant progress in trapping and cooling of single atoms and ions. This progress allows to explore in the most intimate detail the ways in which light interacts with atoms and to measure spectral properties and quantum effects with a large precision. Moreover, it allows to perform subtle tests of quantum mechanics on the single atom and single photon scale which were hardly even imaginable as ``thought experiments'' a few years ago.

This book covers the main ideas, methods, recent developments and applications of quantum-limit optical spectroscopy to quantum information, resolution spectroscopy, measurements beyond quantum limits, measurement of decoherence and entanglement. Quantum-limit spectroscopy lies at the frontier of current experimental and theoretical techniques, and is one of the areas of atomic spectroscopy where the quantization of the field is essential to predict and interpret the existing experimental results. Currently, there is an increasing interest in quantum and precision spectroscopy both theoretically and experimentally, due to a significant progress in trapping and cooling of single atoms and ions. This progress allows to explore in the most intimate detail the ways in which light interacts with atoms and to measure spectral properties and quantum effects with a large precision. Moreover, it allows to perform subtle tests of quantum mechanics on the single atom and single photon scale which were hardly even imaginable as ``thought experiments'' a few years ago.

Readers studying the abstract field of quantum physics need to solve plenty of practical, especially quantitative, problems. This book contains tutorial problems with solutions for the textbook Quantum Physics for Beginners. It places emphasis on basic problems of quantum physics together with some instructive, simulating, and useful applications. A considerable range of complexity is presented by these problems, and not too many of them can be solved using formulas alone.

Atomic correlations have been studied in physics for over 50 years and known as collective effects until recently when they came to be recognized as a source of entanglement. This is the first book that contains detailed and comprehensive analysis of two currently extensively studied subjects of atomic and quantum physics atomic correlations and their relations to entanglement between atoms or atomic systems along with the newest developments in these fields.

This book assembles accounts of many phenomena related to or resulting from atomic correlations. The essential language of the book is in terms of density matrices and master equations that provide detailed theoretical treatments and experimental analysis of phenomena such as entanglement between atoms, spontaneously or externally induced atomic coherence, engineering of atomic correlations, storage and controlled transfer of correlations, and dynamics of correlated systems."

Covers the new field of squeezing in quantum fields, encompassing all types of systems in which quantum fluctuations are reduced below those in the normal vacuum state. The first comprehensive overview of the field, it presents the currently known techniques of generating squeezed photon fields, together with treatments of matter field squeezing. Both theory and experiments are treated, together with applications to communications and measurement.

The ?eld that encompasses the term "quantum interference" combines a number of separate concepts, and has a variety of manifestations in d- ferent areas of physics. In the sense considered here, quantum interference is concerned with coherence and correlation phenomena in radiation ?elds and between their sources. It is intimately connected with the phenomenon of non-separability (or entanglement) in quantum mechanics. On account of this, it is obvious that quantum interference may be regarded as a com- nent of quantum information theory, which investigates the ability of the electromagnetic ?eld to transfer information between correlated (entangled) systems. Since it is important to transfer information with the minimum of corruption, the theory of quantum interference is naturally related to the theory of quantum ?uctuations and decoherence. Since the early days of quantum mechanics, interference has been - scribed as the real quantum mystery. Feynman, in his famous introduction to the lectures on the single particle superposition principle, referred in the following way to the phenomenon of interference: "it has in it the heart of quantum mechanics", and it is really 'the only mystery' of quantum mech- ics. With the development of experimental techniques, it has been possible to carry out many of the early Gedanken experiments that played an important role in developing our understanding of the fundamentals of quantum int- ference and entanglement. Despite its long history, quantum interference still challenges our understanding, and continues to excite our imagination.

The ?eld that encompasses the term "quantum interference" combines a number of separate concepts, and has a variety of manifestations in d- ferent areas of physics. In the sense considered here, quantum interference is concerned with coherence and correlation phenomena in radiation ?elds and between their sources. It is intimately connected with the phenomenon of non-separability (or entanglement) in quantum mechanics. On account of this, it is obvious that quantum interference may be regarded as a com- nent of quantum information theory, which investigates the ability of the electromagnetic ?eld to transfer information between correlated (entangled) systems. Since it is important to transfer information with the minimum of corruption, the theory of quantum interference is naturally related to the theory of quantum ?uctuations and decoherence. Since the early days of quantum mechanics, interference has been - scribed as the real quantum mystery. Feynman, in his famous introduction to the lectures on the single particle superposition principle, referred in the following way to the phenomenon of interference: "it has in it the heart of quantum mechanics," and it is really 'the only mystery' of quantum mech- ics. With the development of experimental techniques, it has been possible to carry out many of the early Gedanken experiments that played an important role in developing our understanding of the fundamentals of quantum int- ference and entanglement. Despite its long history, quantum interference still challenges our understanding, and continues to excite our imagination.

The subject of this book is the new field of squeezing in quantum fields. This general area includes all types of systems in which quantum fluctuations are reduced below those in the normal vacuum state. The book covers the main currently known techniques of generating squeezed photon fields, together with some treatment of matter field squeezing. Both theory and experiments are covered, together with applications to communications and measurement. The chapters of the book are written by the foremost international experts in the field, and their coverage extends from general introductory material, to the most recent developments.

The textbook covers the background theory of various effects discussed from first principles, as clearly as possible, to introduce students to the main ideas of quantum physics and to teach the basic mathematical methods and techniques used in the fields of advanced quantum physics, atomic physics, laser physics, nanotechnology, quantum chemistry, and theoretical mathematics. Many of the predictions of quantum physics appear to be contrary to our intuitive perceptions, and the student will learn how it comes about that microscopic objects (particles) behave in unusual ways that are called quantum effects, what we mean by quantum, and where this idea came from. The textbook is supplemented with Problems and Solutions in Quantum Physics, which contains a wide range of tutorial problems from simple confidence builders to fairly challenging problems that provide adequate understanding of the basic concepts of quantum physics.