Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session E62: The Author in Dialogue: Jeffrey Bub's Bananaworld.Invited Live Undergrad Friendly
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Sponsoring Units: FHP Chair: Michel Janssen, University of Minnesota |
Tuesday, March 16, 2021 8:00AM - 8:36AM Live |
E62.00001: Pragmatism: a natural home for information-theoretic interpretations of quantum theory? Invited Speaker: Leah Henderson Interpretations of quantum theory are often divided into realist and instrumentalist camps. Dominant realist interpretations include the Everett (many worlds) interpretation, the de Broglie-Bohm interpretation and the GRW theory. The tradition of classical American pragmatism, with origins in the work of Peirce, Dewey and James, provides the philosophical basis for a ‘third way’ which is neither instrumentalist nor realist in the traditional sense. Some recent interpretations of quantum theory may be seen as attempts to occupy the kind of philosophical position that the pragmatists opened up. These include the information theoretic interpretation presented by Jeff Bub in Bananaworld and the QBist interpretation due to Chris Fuchs, Rüdiger Schack and others. In the case of QBism, there are clear lines of historical influence from the pragmatist philosophers. Both interpretations are also closely connected to ongoing developments in physics. They draw on the resources of the burgeoning field of quantum information theory and on ongoing efforts in the foundations of quantum theory to reaxiomatise the theory in operationalist or information-theoretic terms. |
Tuesday, March 16, 2021 8:36AM - 9:12AM Live |
E62.00002: Elliptopes and polyhedra: quantum correlations and their classical simulations Invited Speaker: Michael Janas I use correlation arrays, the workhorse of Bub's Bananaworld, to analyze the correlations found in an experimental setup due to Mermin for measurements on the singlet state of a pair of spin-1/2 particles. Adopting an approach pioneered by Pitowsky and promoted in Bananaworld, I show that the class of correlations allowed by quantum mechanics in this setup can be represented geometrically as an elliptope in a non-signaling cube. I then introduce special raffles to determine which of these quantum correlations are allowed by local hidden-variable theories. The subclass of the quantum correlations that can be simulated in this way can be represented geometrically by a tetrahedron inscribed within the elliptope. I extend this analysis to the singlet state of two particles with higher spin. The class of correlations allowed by quantum mechanics in this case is still represented by the elliptope; the subclass of those whose main features I can simulate with my raffles can be represented by polyhedra that, with increasing spin, take up more and more of the volume of the elliptope. The elliptope is thus a general constraint on correlations of the kind studied in this Mermin setup, a result which predates quantum mechanics and was already recognized by the statistician Yule in 1896. |
Tuesday, March 16, 2021 9:12AM - 9:48AM Live |
E62.00003: Interpreting quantum mechanics Invited Speaker: Michael Cuffaro Inspired by Jeffrey Bub's book: Bananaworld: Quantum Mechanics for Primates, we present our own take on the information-theoretic interpretation of quantum mechanics. On our view, the kinematics of quantum mechanics represents a new framework for doing physics, and it is in the provision of this new framework, and in the consequences that follow from it, that quantum mechanics' fundamental significance for physics lies. We take quantum mechanics to be about probabilities in two senses. First: the state specification of a given system yields, in general, only the probability that a selected observable will take on a particular value when we query the system concerning it. Second: The probability distributions associated with individual observables cannot be embedded into a global prior probability distribution over them all. We begin the talk by commenting on the nature of our derivation of the derivation of the space of quantum correlations for a special but informative case study, highlighting the way in which the `principle-theoretic' and `constructive approaches' to physics work together to yield understanding of the physical world. We then argue that the insight yielded by that derivation is that the fundamental novelty of the quantum mode of description can be located in the kinematics rather than in the dynamics of the theory. We then consider the topic of measurement and the puzzle it presents. We argue that the physical significance of the puzzle of measurement as well as the physical account quantum mechanics provides of particular measurements flow naturally from the constraints that quantum mechanics' kinematical core imposes on our representations of quantum systems. Along the way we will reflect on the conception of the world that we take to be suggested by these constraints. The talk will be based on joint work with Michael Janas and Michel Janssen. |
Tuesday, March 16, 2021 9:48AM - 10:24AM Live |
E62.00004: Bananaworld: quantum mechanics for primates Invited Speaker: Jeffrey Bub In spite of the title, Bananaworld is intended to be a serious book about quantum entanglement: what it is, what people have said about it, and what you can do with it. The idea was to bring out the difference between classical and quantum mechanics by considering the extent to which it is possible to simulate the correlation of a Popescu-Rohrlich (PR) nonlocal box with various resources, quantum or classical. Bell’s nonlocality theorem is essentially a proof that the probability of a successful simulation with classical resources is at most .75, while the probability with quantum resources increases to about .85. The bananas were a way of showing the banality of this hypothetical correlation for an imagined pair of PR-entangled bananas in terms of a correlation between peeling from either of the two ends of a banana and two possible tastes. As an afterthought, I added a final chapter about interpretations of quantum mechanics and the measurement problem. I wasn’t satisfied with my take on this in the first edition of the book, so I re-wrote the chapter for the revised paperback edition. I’ll talk about what I was trying to do in the book, and my current view about the issues in the final, still problematic chapter. |
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