This chapter presents some basic ideas and the features of quantum gravity. It gives a compact summary of fundamental ideas of the approaches of semiclassical gravity, loop quantum gravity and string theory. Reconstructing the quantum state of a system on another system of the same type at a distant place is termed as quantum teleportation. Quantum Zeno effect is important in understanding quantum theory of measurement and is in fact a vital tool in quantum computing. Quantum cosmology is considered an application of quantum mechanics to the universe as a whole. The classical cosmology theory is mainly based on the cosmological principle and the expansion of the universe. George Antonovich Gamow and his collaborators Ralph Asher Alpher and Robert Herman proposed the Big-Bang model of the universe to account for the abundances of the elements. Cosmic inflation is based on the hypothesis that the early universe underwent an extremely rapid expansion.
This chapter presents some basic ideas and the features of quantum gravity. It gives a compact summary of fundamental ideas of the approaches of semiclassical gravity, loop quantum gravity and string theory. Reconstructing the quantum state of a system on another system of the same type at a distant place is termed as quantum teleportation. Quantum Zeno effect is important in understanding quantum theory of measurement and is in fact a vital tool in quantum computing. Quantum cosmology is considered an application of quantum mechanics to the universe as a whole. The classical cosmology theory is mainly based on the cosmological principle and the expansion of the universe. George Antonovich Gamow and his collaborators Ralph Asher Alpher and Robert Herman proposed the Big-Bang model of the universe to account for the abundances of the elements. Cosmic inflation is based on the hypothesis that the early universe underwent an extremely rapid expansion.
This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book reviews classical physical and quantum theories for nonspecialists, building on the basics to introduce recent advances. A definition of physical is included for specialists also to consider. The book analyzes quantum theory interpretations, revealing a developmental progression from the standard, many-worlds, decoherence/consistent histories, quantum probability, quantum information field, and transactional interpretations to neorealism. It outlines a new holistic interpretation of quantum theory; of major significance is the subtle concept of levels of spacetime. The book considers loop quantum gravity, string, inflationary big bang, and unified field theories. The diverse interpretations are in large part due to focusing on the observed as the only reality: the process of observing and the observer were practically ignored.
Quantum Mechanics II: Advanced Topics offers a comprehensive exploration of the state-of-the-art in various advanced topics of current research interest. A follow-up to the authors’ introductory book Quantum Mechanics I: The Fundamentals, this book expounds basic principles, theoretical treatment, case studies, worked-out examples and applications of advanced topics including quantum technologies. A thoroughly revised and updated this unique volume presents an in-depth and up-to-date progress on the growing topics including latest achievements on quantum technology. In the second edition six new chapters are included and the other ten chapters are extensively revised. Features Covers classical and quantum field theories, path integral formalism and supersymmetric quantum mechanics. Highlights coherent and squeezed states, Berry’s phase, Aharonov—Bohm effect and Wigner function. Explores salient features of quantum entanglement and quantum cryptography. Presents basic concepts of quantum computers and the features of no-cloning theorem and quantum cloning machines. Describes the theory and techniques of quantum tomography, quantum simulation and quantum error correction. Introduces other novel topics including quantum versions of theory of gravity, cosmology, Zeno effect, teleportation, games, chaos and steering. Outlines the quantum technologies of ghost imaging, detection of weak amplitudes and displacements, lithography, metrology, teleportation of optical images, sensors, batteries and internet. Contains several worked-out problems and exercises in each chapter. Quantum Mechanics II: Advanced Topics addresses various currently emerging exciting topics of quantum mechanics. It emphasizes the fundamentals behind the latest cutting-edge developments to help explain the motivation for deeper exploration. The book is a valuable resource for graduate students in physics and engineering wishing to pursue research in quantum mechanics.
Scope of this book Quantum mechanics is a difficult subject, and this book is intended to help the reader overcome the main difficulties in the way to understanding it. The first part of the book, Chs. 2–16, contains a systematic presentation of the basic principles of quantum theory, along with a number of examples which illustrate how these principles apply to particular quantum systems. The applications are, for the most part, limited to toy models whose simple structure allows one to see what is going on without using complicated mathematics or lengthy formulas. The principles themselves, however, are formulated in such a way that they can be applied to (almost) any nonrelativistic quantum system. In the second part of the book, Chs. 17–25, these principles are applied to quantum measurements and various quantum paradoxes, subjects which give rise to serious conceptual problems when they are not treated in a fully consistent manner. The final chapters are of a somewhat different character. Chapter 26 on decoherence and the classical limit of quantum theory is a very sketchy introduction to these important topics along with some indication as to how the basic principles presented in the first part of the book can be used for understanding them. Chapter 27 on quantum theory and reality belongs to the interface between physics and philosophy and indicates why quantum theory is compatible with a real world whose existence is not dependent on what scientists think and believe, or the experiments they choose to carry out. The Bibliography contains references for those interested in further reading or in tracing the origin of some of the ideas presented in earlier chapters.
Recent developments in quantum theory have focused attention on fundamental questions, in particular on whether it might be necessary to modify quantum mechanics to reconcile quantum gravity and general relativity. This book is based on a conference held in Oxford in the spring of 1984 to discuss quantum gravity. It brings together contributors who examine different aspects of the problem, including the experimental support for quantum mechanics, its strange and apparently paradoxical features, its underlying philosophy, and possible modifications to the theory.
When quantum mechanics was developed in the '20s of the last century another revolution in physics was just starting. It began with the discovery that the universe is expanding. For a long time quantum mechanics and cosmology developed independently of one another. Yet the very discovery of the expansion would eventually draw the two subjects together because it implied the big bang where quantum mechanics wasimportant for cosmology and for understanding and predicting our observations of the universe today. Textbook (Copenhagen) formulations of quantum mechanics are inadequate for cosmology for at least four reasons: 1) They predict the outcomes of measurements made by observers. But in the very early universe no measurements were being made and no observers were around to make them. 2) Observers were outside of the system being measured. But we are interested in a theory of the whole universe where everything, including observers, are inside. 3) Copenhagen quantum mechanics could not retrodict the past. But retrodicting the past to understand how the universe began is the main task of cosmology. 4) Copenhagen quantum mechanics required a fixed classical spacetime geometry not least to give meaning to the time in the Schrödinger equation. But in the very early universe spacetime is fluctuating quantum mechanically (quantum gravity) and without definite value. A formulation of quantum mechanics general enough for cosmology was started by Everett and developed by many. That effort has given us a more general framework that is adequate for cosmology --- decoherent (or consistent) histories quantum theory in the context of semiclassical quantum gravity. Copenhagen quantum theory is an approximation to this more general quantum framework that is appropriate for measurement situations. We discuss whether further generalization may still be required.