Causality is central to understanding the mechanisms of nature: some event "A" is the cause of another event “B”. Surprisingly, causality does not follow this simple rule in quantum physics: due to to quantum superposition we might be led to believe that "A causes B” and that "B causes A”. This idea is not only important to the foundations of physics but also leads to practical advantages: a quantum circuit with such indefinite causality performs computationally better than one with definite causality. This thesis provides one of the first comprehensive introductions to quantum causality, and presents a number of advances. It provides an extension and generalization of a framework that enables us to study causality within quantum mechanics, thereby setting the stage for the rest of the work. This comprises: mathematical tools to define causality in terms of probabilities; computational tools to prove indefinite causality in an experiment; means to experimentally test particular causal structures; and finally an algorithm that detects the exact causal structure in an quantum experiment.

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.

"Causality in science"--Provided by publisher.

In this classic, David Bohm was the first to offer us his causal interpretation of the quantum theory. Causality and Chance in Modern Physics continues to make possible further insight into the meaning of the quantum theory and to suggest ways of extending the theory into new directions.

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.