9 found
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  1. Subjective probability and quantum certainty.Carlton M. Caves, Christopher A. Fuchs & Rüdiger Schack - 2007 - Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics 38 (2):255-274.
    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 (...)
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  2. Respecting One’s Fellow: QBism’s Analysis of Wigner’s Friend.John B. DeBrota, Christopher A. Fuchs & Rüdiger Schack - 2020 - Foundations of Physics 50 (12):1859-1874.
    According to QBism, quantum states, unitary evolutions, and measurement operators are all understood as personal judgments of the agent using the formalism. Meanwhile, quantum measurement outcomes are understood as the personal experiences of the same agent. Wigner’s conundrum of the friend, in which two agents ostensibly have different accounts of whether or not there is a measurement outcome, thus poses no paradox for QBism. Indeed the resolution of Wigner’s original thought experiment was central to the development of QBist thinking. The (...)
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  3. A Quantum-Bayesian Route to Quantum-State Space.Christopher A. Fuchs & Rüdiger Schack - 2011 - Foundations of Physics 41 (3):345-356.
    In the quantum-Bayesian approach to quantum foundations, a quantum state is viewed as an expression of an agent’s personalist Bayesian degrees of belief, or probabilities, concerning the results of measurements. These probabilities obey the usual probability rules as required by Dutch-book coherence, but quantum mechanics imposes additional constraints upon them. In this paper, we explore the question of deriving the structure of quantum-state space from a set of assumptions in the spirit of quantum Bayesianism. The starting point is the representation (...)
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    Gleason-Type Derivations of the Quantum Probability Rule for Generalized Measurements.Carlton M. Caves, Christopher A. Fuchs, Kiran K. Manne & Joseph M. Renes - 2004 - Foundations of Physics 34 (2):193-209.
    We prove a Gleason-type theorem for the quantum probability rule using frame functions defined on positive-operator-valued measures, as opposed to the restricted class of orthogonal projection-valued measures used in the original theorem. The advantage of this method is that it works for two-dimensional quantum systems and even for vector spaces over rational fields—settings where the standard theorem fails. Furthermore, unlike the method necessary for proving the original result, the present one is rather elementary. In the case of a qubit, we (...)
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  5. Bayesian conditioning, the reflection principle, and quantum decoherence.Christopher A. Fuchs & Rüdiger Schack - 2012 - In Yemima Ben-Menahem & Meir Hemmo (eds.), Probability in Physics. Springer. pp. 233--247.
    The probabilities a Bayesian agent assigns to a set of events typically change with time, for instance when the agent updates them in the light of new data. In this paper we address the question of how an agent's probabilities at different times are constrained by Dutch-book coherence. We review and attempt to clarify the argument that, although an agent is not forced by coherence to use the usual Bayesian conditioning rule to update his probabilities, coherence does require the agent's (...)
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  6. Negativity Bounds for Weyl–Heisenberg Quasiprobability Representations.John B. DeBrota & Christopher A. Fuchs - 2017 - Foundations of Physics 47 (8):1009-1030.
    The appearance of negative terms in quasiprobability representations of quantum theory is known to be inevitable, and, due to its equivalence with the onset of contextuality, of central interest in quantum computation and information. Until recently, however, nothing has been known about how much negativity is necessary in a quasiprobability representation. Zhu :120404, 2016) proved that the upper and lower bounds with respect to one type of negativity measure are saturated by quasiprobability representations which are in one-to-one correspondence with the (...)
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  7. Properties of QBist State Spaces.D. M. Appleby, Åsa Ericsson & Christopher A. Fuchs - 2011 - Foundations of Physics 41 (3):564-579.
    Every quantum state can be represented as a probability distribution over the outcomes of an informationally complete measurement. But not all probability distributions correspond to quantum states. Quantum state space may thus be thought of as a restricted subset of all potentially available probabilities. A recent publication (Fuchs and Schack, arXiv:0906.2187v1, 2009) advocates such a representation using symmetric informationally complete (SIC) measurements. Building upon this work we study how this subset—quantum-state space—might be characterized. Our leading characteristic is that the inner (...)
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  8.  24
    Introduction.Jeffrey Bub & Christopher A. Fuchs - 2003 - Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics 34 (3):339-341.
    Special Issue on Quantum Information and Computation.
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  9.  25
    Preface to Special Issue: Quantum Information Revolution: Impact to Foundations.Christopher A. Fuchs & Andrei Khrennikov - 2020 - Foundations of Physics 50 (12):1757-1761.
    The year 2019 witnessed the 20th Jubileum of the Växjö conference series on quantum foundations and probability in physics. This has been the longest running series of conferences on the subject in history. Many old and new friendships were forged at Linnaeus University and the beautiful surrounding lakes of Småland, where once yearly everyone gathers to renew the debate and report their latest progress. 2019 also represents the Porcelain Anniversary—18 years—of the point of view on quantum theory known as QBism. (...)
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