Christopher G. Timpson provides the first full-length philosophical treatment of quantum information theory and the questions it raises for our understanding of the quantum world. He argues for an ontologically deflationary account of the nature of quantum information, which is grounded in a revisionary analysis of the concepts of information.

In contrast to the theories of relativity, quantum mechanics is not yet based on a generally accepted conceptual foundation. It is proposed here that the missing principle may be identified through the observation that all knowledge in physics has to be expressed in propositions and that therefore the most elementary system represents the truth value of one proposition, i.e., it carries just one bit of information. Therefore an elementary system can only give a definite result in one specific measurement. The (...) irreducible randomness in other measurements is then a necessary consequence. For composite systems entanglement results if all possible information is exhausted in specifying joint properties of the constituents. (shrink)

I Physics of Information Information, Physics, Quantum: The Search for Links John Archibald Wheeler Information from Quantum Measurements Benjamin Schumacher Local Accessibility of Quantum States William K. Wootters The Entropy of Black Holes V. F. Mukhanov Some Simple Consequences of the Loss of Information in a Spacetime with a Horizon Shin Takagi Why is the Physical World so Comprehensible? P. C. W. Davies II Laws of Physics and Laws of Computation Algorithmic Information Content, Church-Turing Thesis, Physical Entropy, and Maxwell’s Demon (...) W. E. Zurek Entropy and Information: How Much Information is Needed to Assign a Probability? Carlton M. Caves Complexity of Models J. Rissanen Laws and Boundary Conditions C. H. Woo How to Define Complexity in Physics, and Why Charles H. Bennett III Complexity and Evolution Requirements for Evolvability in Complex Systems: Orderly Dynamics and Frozen Components Stuart A. Kauffman Valuable Information Seth Lloyd Non-Equilibrium Polymers, Entropy, and Algorithmic Information Dilip K. Kondepudi The Dynamics of Complex Computational Systems Tad Hogg Computation at the Onset of Chaos James P. Crutchfield and Karl Young IV Physics of Computation Parallel Quantum Computation Norman Margolus Information Processing at the Molecular Level: Possible Realizations and Physical Constraints W. G. Teich and G. Mahler How Cheap Can Mechanics’ First Principles Be? Tommaso Toffoli Intermittent Fluctuations and Complexity Xiao-Jing Wang Information Processing in Visual Perception A. Zee V Probability, Entropy, and Quantum Thermodynamic Constraints on Quantum Axioms Asker Peres Entropy and Quantum Mechanics M. Hossein Páriovi Einstein Completion of Quantum Mechanics Made Falsifiable O. E. Rossler Quantum Mechanics and Algorithmic Complexity J. W. Barrett Probability in Quantum Theory E. T. Jaynes Quantum Measurements and Entropy H. D. Zeh VI Quantum Theory and Measurement Quantum Mechanics in the Light of Quantum Cosmology Murray Gell-Mann and James B. Hartle Information Dissipation in Quantum Cosmology and the Emergence of Classical Spacetime Jonathan J. Halliwell The Quantum Mechanics of Self-Measurement David Z. Albert The Quantum-Classical Correspondence in Light of Classi- cal Bell’s and Quantum Tsirelson’s Inequalities X. A. Khalfin Some Progress in Measurement Theory: The Logical Inter- pretation of Quantum Mechanics Roland Omnes. (shrink)

"Science is rooted in conversations," wrote Werner Heisenberg, one of the twentieth century's great physicists. In Quantum Dialogue, Mara Beller shows that science is rooted not just in conversation but in disagreement, doubt, and uncertainty. She argues that it is precisely this culture of dialogue and controversy within the scientific community that fuels creativity. Beller draws her argument from her radical new reading of the history of the quantum revolution, especially the development of the Copenhagen interpretation. One of several competing (...) approaches, this version succeeded largely due to the rhetorical skills of Niels Bohr and his colleagues. Using extensive archival research, Beller shows how Bohr and others marketed their views, misrepresenting and dismissing their opponents as "unreasonable" and championing their own not always coherent or well-supported position as "inevitable." Quantum Dialogue, winner of the 1999 Morris D. Forkosch Prize of the Journal of the History of Ideas, will fascinate everyone interested in how stories of "scientific revolutions" are constructed and "scientific consensus" achieved. "[A]n intellectually stimulating piece of work, energised by a distinct point of view."—Dipankar Home, Times Higher Education Supplement "[R]emarkable and original. . . . [Beller's] arguments are thoroughly supported and her conclusions are meticulously argued. . . . This is an important book that all who are interested in the emergence of quantum mechanics will want to read."—William Evenson, History of Physics Newsletter. (shrink)

In the Bayesian approach to quantum mechanics, probabilities—and thus quantum states—represent an agent’s degrees of belief, rather than corresponding to objective properties of physical systems. In this paper we investigate the concept of certainty in quantum mechanics. Particularly, we show how the probability-1 predictions derived from pure quantum states highlight a fundamental difference between our Bayesian approach, on the one hand, and Copenhagen and similar interpretations on the other. We first review the main arguments for the general claim that probabilities (...) always represent degrees of belief. We then argue that a quantum state prepared by some physical device always depends on an agent’s prior beliefs, implying that the probability-1 predictions derived from that state also depend on the agent’s prior beliefs. Quantum certainty is therefore always some agent’s certainty. Conversely, if facts about an experimental setup could imply agent-independent certainty for a measurement outcome, as in many Copenhagen-like interpretations, that outcome would effectively correspond to a preexisting system property. The idea that measurement outcomes occurring with certainty correspond to preexisting system properties is, however, in conflict with locality. We emphasize this by giving a version of an argument of Stairs [(1983). Quantum logic, realism, and value-definiteness. Philosophy of Science, 50, 578], which applies the Kochen–Specker theorem to an entangled bipartite system. (shrink)

In the course of the discussion, Professor Quine pinpoints the difficulties involved in translation, brings to light the anomalies and conflicts implicit in our ...

This report reviews what quantum physics and information theory have to tell us about the age-old question, How come existence? No escape is evident from four conclusions: (1) The world cannot be a giant machine, ruled by any preestablished continuum physical law. (2) There is no such thing at the microscopic level as space or time or spacetime continuum. (3) The familiar probability function or functional, and wave equation or functional wave equation, of standard quantum theory provide mere continuum idealizations (...) and by reason of this circumstance conceal the information-theoretic source from which they derive. (4) No element in the description of physics shows itself as closer to primordial than the elementary quantum phenomenon, that is, the elementary device-intermediated act of posing a yes-no physical question and eliciting an answer or, in brief, the elementary act of observer-participancy. Otherwise stated, every physical quantity, every it, derives its ultimate significance from bits, binary yes-or-no indications, a conclusion which we epitomize in the phrase, it from bit. (shrink)

Quantum Information Theory and the Foundations of Quantum Mechanics is a conceptual analysis of one of the most prominent and exciting new areas of physics, providing the first full-length philosophical treatment of quantum information theory and the questions it raises for our understanding of the quantum world. -/- Beginning from a careful, revisionary, analysis of the concepts of information in the everyday and classical information-theory settings, Christopher G. Timpson argues for an ontologically deflationary account of the nature of quantum information. (...) Against what many have supposed, quantum information can be clearly defined (it is not a primitive or vague notion) but it is not part of the material contents of the world. Timpson's account sheds light on the nature of nonlocality and information flow in the presence of entanglement and, in particular, dissolves puzzles surrounding the remarkable process of quantum teleportation. In addition it permits a clear view of what the ontological and methodological lessons provided by quantum information theory are; lessons which bear on the gripping question of what role a concept like information has to play in fundamental physics. Topics discussed include the slogan 'Information is Physical', the prospects for an informational immaterialism (the view that information rather than matter might fundamentally constitute the world), and the status of the Church-Turing hypothesis in light of quantum computation. -/- With a clear grasp of the concept of information in hand, Timpson turns his attention to the pressing question of whether advances in quantum information theory pave the way for the resolution of the traditional conceptual problems of quantum mechanics: the deep problems which loom over measurement, nonlocality and the general nature of quantum ontology. He marks out a number of common pitfalls to be avoided before analysing in detail some concrete proposals, including the radical quantum Bayesian programme of Caves, Fuchs, and Schack. One central moral which is drawn is that, for all the interest that the quantum information-inspired approaches hold, no cheap resolutions to the traditional problems of quantum mechanics are to be had. (shrink)

We show that three fundamental information-theoretic constraints -- the impossibility of superluminal information transfer between two physical systems by performing measurements on one of them, the impossibility of broadcasting the information contained in an unknown physical state, and the impossibility of unconditionally secure bit commitment -- suffice to entail that the observables and state space of a physical theory are quantum-mechanical. We demonstrate the converse derivation in part, and consider the implications of alternative answers to a remaining open question about (...) nonlocality and bit commitment. (shrink)

What is commonly known as the Copenhagen interpretation of quantum mechanics, regarded as representing a unitary Copenhagen point of view, differs significantly from Bohr's complementarity interpretation, which does not employ wave packet collapse in its account of measurement and does not accord the subjective observer any privileged role in measurement. It is argued that the Copenhagen interpretation is an invention of the mid‐1950s, for which Heisenberg is chiefly responsible, various other physicists and philosophers, including Bohm, Feyerabend, Hanson, and Popper, having (...) further promoted the invention in the service of their own philosophical agendas. (shrink)

We present a toy theory that is based on a simple principle: the number of questions about the physical state of a system that are answered must always be equal to the number that are unanswered in a state of maximal knowledge. Many quantum phenomena are found to have analogues within this toy theory. These include the noncommutativity of measurements, interference, the multiplicity of convex decompositions of a mixed state, the impossibility of discriminating nonorthogonal states, the impossibility of a universal (...) state inverter, the distinction between bipartite and tripartite entanglement, the monogamy of pure entanglement, no cloning, no broadcasting, remote steering, teleportation, entanglement swapping, dense coding, mutually unbiased bases, and many others. The diversity and quality of these analogies is taken as evidence for the view that quantum states are states of incomplete knowledge rather than states of reality. A consideration of the phenomena that the toy theory fails to reproduce, notably, violations of Bell inequalities and the existence of a Kochen-Specker theorem, provides clues for how to proceed with this research program. (shrink)

Recently, Brukner and Zeilinger 3354) have claimed that the Shannon information is not well defined as a measure of information in quantum mechanics, adducing arguments that seek to show that it is inextricably tied to classical notions of measurement. It is shown here that these arguments do not succeed: the Shannon information does not have problematic ties to classical concepts. In a further argument, Brukner and Zeilinger compare the Shannon information unfavourably to their preferred information measure, I , with regard (...) to the definition of a notion of “total information content.” This argument is found unconvincing and the relationship between individual measures of information and notions of “total information content” investigated. We close by considering the prospects of Zeilinger's Foundational Principle as a foundational principle for quantum mechanics. (shrink)