This book presents a distinctive way of understanding quantum correlations beyond entanglement, introducing readers to this less explored yet very fundamental aspect of quantum theory. It takes into account most of the new ideas involving quantum phenomena, resources, and applications without entanglement, both from a theoretical and an experimental point of view. This book serves as a reference for both beginner students and experienced researchers in physics and applied mathematics, with an interest in joining this novel venture towards understanding the quantum nature of the world.

Quantum correlations are not restricted to the well known entanglement investigated in Bell-type experiments. Other forms of correlations, for example quantum discord, have recently been shown to play an important role in several aspects of quantum information theory. First experiments also support these findings. This book is an introduction into this up-and-coming research field and its likely impact on quantum technology. After giving a general introduction to the concept of quantum correlations and their role in quantum information theory, the author describes a number of pertinent results and their implications.

This text revolves around a new and unusual view on the most fundamental puzzle of physics. It focusses on the key aspect that makes the role of the time dimension fundamentally different: causality. It deals on the one hand with general relativity, and on the other hand with quantum theory. The implicit and intuitive way by which causality is usually taken for granted is just made explicit and less self-evident, shedding a new light on the gravity-quantum conflict. The case is made that gravity is a necessary condition for a causal universe. But upon turning to the "pure" unitary quantum physics explaining the nature of matter one is dealing with the strictly a-causal time expressed through the thermal quantum field theory machinery. When this a-causal microscopic and causal macroscopic world meet, one encounters the wavefunction collapse, that itself may be rooted in the quantum-gravity conflict. Modern ideas are discussed resting on eigenstate thermalization showing how this may lie eventually at the origin of irreversible thermodynamics, with its famous second law setting also a direction of time. The case is anchored in the sophisticated modern mathematical machinery of both general relativity and quantum physics which is normally barely disseminated beyond the theoretical physics floors. The book is unique in the regard that the consequences of this machinery - Riemannian geometry and Penrose diagrams, thermal quantum fields, quantum non-equilibrium and so forth -- are explained in an original, descriptive language conveying the conceptual consequences while avoiding mathematical technicalities.

Philosophers have discussed the relationship of cause and effect from ancient times through our own. Prior to the work of Niels Bohr, these discussions presupposed that successful causal attribution implies explanation. The success of quantum theory challenged this presupposition. Bohr introduced a principle of complementarity that provides a new way of looking at causality and explanation.In this succinct review of the history of these discussions, John Losee presents the philosophical background of debates over the cause-effect relation. He reviews the positions of Aristotle, Rene Descartes, Isaac Newton, David Hume, Immanuel Kant, and John Stuart Mill. He shows how nineteenth-century theories in physics and chemistry were informed by a dominant theory of causality and how specific developments in physics provided the background for the emergence of quantum theory.Problems created for the causality implies explanation thesis by the emergence of quantum theory are reviewed in detail. Losee evaluates Bohr's proposals to apply a principle of complementarity within physics, biology, and psychology. He also discusses the feasibility of using complementarity as a principle of interpretation within Christian theology. This volume, which includes an in-depth index, is an essential addition to the libraries of advanced undergraduate and graduate students, philosophers, and those interested in causality and explanation.

There is no sharp dividing line between the foundations of physics and philosophy of physics. This is especially true for quantum mechanics. The debate on the interpretation of quantum mechanics has raged in both the scientific and philosophical communities since the 1920s and continues to this day. (We shall understand the unqualified term ‘quantum mechanics’ to mean the mathematical formalism, i. e. laws and rules by which empirical predictions and theoretical advances are made. ) There is a popular rendering of quantum mechanics which has been publicly endorsed by some well known physicists which says that quantum mechanics is not only 1 more weird than we imagine but is weirder than we can imagine. Although it is readily granted that quantum mechanics has produced some strange and counter-intuitive results, the case will be presented in this book that quantum mechanics is not as weird as we might have been led to believe! The prevailing theory of quantum mechanics is called Orthodox Quantum Theory (also known as the Copenhagen Interpretation). Orthodox Quantum Theory endows a special status on measurement processes by requiring an intervention of an observer or an observer’s proxy (e. g. a measuring apparatus). The placement of the observer (or proxy) is somewhat arbitrary which introduces a degree of subjectivity. Orthodox Quantum Theory only predicts probabilities for measured values of physical quantities. It is essentially an instrumental theory, i. e.

This book provides a description of the evolution of the concepts of causality and time through modern physics considering first relativity theories and them quantum mechanics. Relativity, at least in the form given by Einstein, denies reality of past, present and future and does not indicate a time direction. On the other hand a time direction is indicated by all the phenomena we observe including our own existence. Quantum mechanics seems to indicate a different story. It is argued that, because of its non deterministic character, it is capable to indicate an objective time direction. This occurs through the phenomena of wave function collapse and entanglement which are discussed at length.