Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session X27: Quantum Foundations IIFocus
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Sponsoring Units: DQI Chair: Matthew Pusey, University of Oxford Room: BCEC 160C |
Friday, March 8, 2019 8:00AM - 8:36AM |
X27.00001: Quantum theory cannot consistently describe the use of itself Invited Speaker: Renato Renner Can quantum theory be used to consistently describe an agent who herself uses the theory? If quantum theory was a universally valid theory, applicable to arbitrarily complex systems, then this should clearly be the case. To study the question, we consider a setup consisting of four computers that take the role of agents. They are programmed with the rules of quantum theory, which they use to derive statements about the outcome of particular measurements, as well as about the statements that the other computers derived. We then show that the computers sometimes arrive at contradictory statements. This indicates that quantum theory cannot be extrapolated to complex systems, at least not in a straightforward manner. |
Friday, March 8, 2019 8:36AM - 9:12AM |
X27.00002: Why QBism is immune to no-go theorems Invited Speaker: Ruediger Schack In 2012, Pusey, Barrett and Rudolph published a no-go theorem ruling out a class of ontological models for quantum mechanics. In 2015, the first loop-hole free Bell tests confirmed the assumptions of Bell's theorem, the most famous of all no-go theorems. In 2018, Frauchiger and Renner published a no-go theorem based on the Wigner's friend thought experiment. Because each of these no-go theorems, and their many variants, rule out a number of competing interpretations, QBism has emerged significantly strengthened from these developments. |
Friday, March 8, 2019 9:12AM - 9:24AM |
X27.00003: An incompleteness theorem for physics John Myers, F. Hadi Madjid We show how Gödel's incompleteness theorems have an analog in quantum theory. Gödel's theorems imply endless opportunities for appending axioms to arithmetic, implicitly showing a role for an entity that writes axioms as logically undetermined strings of symbols. There is an analog of these theorems in physics, to do with the set of explanations of given evidence. We prove that the set of explanations of given evidence is uncountably infinite, thereby showing how contact between theory and experiment depends on activity beyond computation and measurement---a physical activity of logically undetermined symbol handling. |
Friday, March 8, 2019 9:24AM - 9:36AM |
X27.00004: Ambiguity in the branching process of Many-Worlds Theories Kathrin Gerhard, Renato Renner Quantum mechanics correctly predicts measurement results and is therefore considered a useful physical theory. However, in a recently proposed thought experiment by D. Frauchiger and R. Renner, agents use quantum theory to describe how other agents use the theory, and contradictory statements appear. |
Friday, March 8, 2019 9:36AM - 9:48AM |
X27.00005: WITHDRAWN ABSTRACT
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Friday, March 8, 2019 9:48AM - 10:00AM |
X27.00006: Small violations of Bell inequalities for multipartite pure random states Cristhiano Silva, Raphael Drumond, Roberto Oliveira For any finite number of parts, measurements and outcomes in a Bell scenario we estimate the probability of random N-qudit pure states to substantially violate any Bell inequality with uniformly bounded coefficients. We prove that under some conditions on the local dimension the probability to find any significant amount of violation goes to zero exponentially fast as the number of parts goes to infinity. In addition, we also prove that if the number of parts is at least 3, this probability also goes to zero as the local Hilbert space dimension goes to infinity. |
Friday, March 8, 2019 10:00AM - 10:12AM |
X27.00007: Hybrid Computation for Consistent Histories Andrew Arrasmith, Lukasz Cincio, Andrew T Sornborger, Patrick J Coles, Wojciech Zurek The consistent histories approach to quantum mechanics can be a valuable tool for studying many physical processes, ranging from the stochastic behavior of molecules to the quantum-to-classical transition. This approach resolves seeming paradoxes and allows us to apply classical logic to sequences of quantum events. Unfortunately, this tool has historically been limited to small systems or simple cases as the computational expense involved exponentially grows with both the system size and with the number of times considered on a classical computer, quickly becoming intractable. To remedy this difficulty, we present a hybrid quantum/classical algorithm suited for noisy intermediate-scale quantum computers that allows us to find and study consistent histories. We demonstrate the performance of this algorithm on the IBM and Rigetti quantum computers, and show a simulated demonstration of what will be possible on larger quantum computers. Finally, we discuss some potential future applications of this algorithm. |
Friday, March 8, 2019 10:12AM - 10:24AM |
X27.00008: WITHDRAWN ABSTRACT
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Friday, March 8, 2019 10:24AM - 10:36AM |
X27.00009: ABSTRACT WITHDRAWN
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Friday, March 8, 2019 10:36AM - 10:48AM |
X27.00010: Observing a Quantum Measurement Walter Lawrence As a model quantum detector system, place a qubit in each path of a Stern-Gerlach apparatus, |
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