# Weekly Papers on Quantum Foundations (27)

This is a list of this week’s papers on quantum foundations published in various journals or uploaded to preprint servers such as arxiv.org and PhilSci Archive.

A comparative review of four formulations of noncommutative quantum mechanics. (arXiv:1603.07176v2 [hep-th] UPDATED)

on 2016-7-02 7:53am GMT

Authors: Laure Gouba

Four formulations of quantum mechanics on noncommutative Moyal phase spaces are reviewed. These are the canonical, path-integral, Weyl-Wigner and systematic formulations. Although all these formulations represent quantum mechanics on a phase space with the same deformed Heisenberg algebra, there are mathematical and conceptual differences which we discuss.

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on 2016-7-02 2:21am GMT

Authors: Alexander Wilce

This paper fails to derive quantum mechanics from a few simple postulates. But it gets very close — and it does so without much exertion. More exactly, I obtain a representation of finite-dimensional probabilistic systems in terms of euclidean Jordan algebras, in a strikingly easy way, from simple assumptions. This provides a framework within which real, complex and quaternionic QM can play happily together, and allows some — but not too much — room for more exotic alternatives. (This is a leisurely summary, based on recent lectures, of material from the papers arXiv:1206:2897 and arXiv:1507.06278, the latter joint work with Howard Barnum and Matthew Graydon. Some further ideas are also explored.)

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Consciousness and Quantum Measurement

Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2016-7-02 12:00am GMT

Broka, Chris (2016) Consciousness and Quantum Measurement. [Preprint]

Observation of the quantum paradox of separation of a single photon from one of its properties

PRA: Fundamental concepts

on 2016-7-01 2:00pm GMT

Author(s): James M. Ashby, Peter D. Schwarz, and Maximilian Schlosshauer

Researchers detected the polarization of a photon separate from the photon itself, just as the grin of Lewis Carroll’s Cheshire cat can appear apart from the cat’s body.

[Phys. Rev. A 94, 012102] Published Fri Jul 01, 2016

The Holographic Quantum

Latest Results for Foundations of Physics

on 2016-7-01 12:00am GMT

Abstract

We present a map of standard quantum mechanics onto a dual theory, that of the classical thermodynamics of irreversible processes. While no gravity is present in our construction, our map exhibits features that are reminiscent of the holographic principle of quantum gravity.

On the Received Realist View of Quantum Mechanics

Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2016-6-29 7:26pm GMT

Sznajderhaus, Nahuel (2016) On the Received Realist View of Quantum Mechanics. [Preprint]

Space from Hilbert Space: Recovering Geometry from Bulk Entanglement. (arXiv:1606.08444v1 [hep-th])

on 2016-6-29 9:34am GMT

Authors: ChunJun CaoSean M. Carroll

We examine how to construct a spatial manifold and its geometry from the entanglement structure of an abstract quantum state in Hilbert space. Given a decomposition of Hilbert space $\mathcal{H}$ into a tensor product of factors, we consider a class of “redundancy-constrained states” in $\mathcal{H}$ that generalize the area-law behavior for entanglement entropy usually found in condensed-matter systems with gapped local Hamiltonians. Using mutual information to define a distance measure on the graph, we employ classical multidimensional scaling to extract the best-fit spatial dimensionality of the emergent geometry. We then show that entanglement perturbations on such emergent geometries naturally give rise to local modifications of spatial curvature which obey a (spatial) analog of Einstein’s equation. The Hilbert space corresponding to a region of flat space is finite-dimensional and scales as the volume, though the entropy (and the maximum change thereof) scales like the area of the boundary. A version of the ER=EPR conjecture is recovered, in that perturbations that entangle distant parts of the emergent geometry generate a configuration that may be considered as a highly quantum wormhole.

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Event Horizon Telescope Observations as Probes for Quantum Structure of Astrophysical Black Holes. (arXiv:1606.07814v1 [astro-ph.HE] CROSS LISTED)

on 2016-6-29 9:33am GMT

Authors: Steven B. GiddingsDimitrios Psaltis

The need for a consistent quantum evolution for black holes has led to proposals that their semiclassical description is modified not just near the singularity, but at horizon or larger scales. If such modifications extend beyond the horizon, they influence regions accessible to distant observeration. Natural candidates for these modifications behave like metric fluctuations, with characteristic length and time scales set by the horizon radius. We investigate the possibility of using the Event Horizon Telescope to observe these effects, if they have a strength sufficient to make quantum evolution consistent with unitarity. We find that such quantum fluctuations can introduce a strong time dependence for the shape and size of the shadow that a black hole casts on its surrounding emission. For the black hole in the center of the Milky Way, detecting the rapid time variability of its shadow will require non-imaging timing techniques. However, for the much larger black hole in the center of the M87 galaxy, a variable black-hole shadow, if present with these parameters, would be readily observable in the individual snapshots that will be obtained by the Event Horizon Telescope.

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Event ontology in quantum mechanics and the problem of emergence

Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2016-6-29 4:33am GMT

Gambini, Rodolfo and Pullin, Jorge (2016) Event ontology in quantum mechanics and the problem of emergence. [Published Article or Volume]

At what time does a quantum experiment have a result?

Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2016-6-29 4:32am GMT

Pashby, Thomas (2016) At what time does a quantum experiment have a result? [Preprint]

Violation of the Born Rule: Implications for Macroscopic Fields

Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2016-6-27 5:20pm GMT

Kastner, Ruth (2016) Violation of the Born Rule: Implications for Macroscopic Fields. [Published Article or Volume]

Macroscopic superpositions as quantum ground states. (arXiv:1606.07712v1 [quant-ph])

on 2016-6-27 4:33am GMT

We study the question of whether a macroscopic superposition can naturally exist as a ground state of some gapped many-body Hamiltonian. We derive an upper bound on the energy gap of an arbitrary physical Hamiltonian provided that its ground state is a superposition of two macroscopic “semi-classical” states. For a large class of such macroscopic superposition states we show that the gap vanishes in the macroscopic limit. Our main result shows an interesting quantitative relation between the order of interaction and separation probability between the two constituents of the superposition. This in turn shows that preparation of a “typical” Schr\”odinger cat-like state by simple cooling to the ground state would require the order of interaction to increase with the size of system. We also discuss our results in the context of quantum spin-lattice models and trapped Bose-Einstein condensates and we find that certain classes of states (e.g. W states), although not usually considered to exhibit macroscopic quantum properties, cannot be ground states of gapped local Hamiltonians.

Which causal scenarios are interesting?. (arXiv:1606.07798v1 [quant-ph])

on 2016-6-27 4:33am GMT

Authors: Jacques Pienaar

A causal scenario is a graph that describes the cause and effect relationships between all relevant variables in an experiment. A scenario is deemed interesting if different operational probabilistic theories give rise to different marginal distributions of the observed variables — a Bell-type experiment is one example. Graphs that are not interesting are boring in a precise sense: the predictions of an arbitrary generalised probabilistic theory (quantum or otherwise) can be reproduced by local hidden variables respecting the causal structure of the graph. Henson, Lal and Pusey (HLP) [New J. Phys. 16, 113043] recently proposed a sufficient condition for a causal scenario to be boring. In this paper we review and propose several sufficient conditions for a graph to be interesting. We first show that existing graphical techniques due to Evans can be used to confirm that many graphs are interesting without having to explicitly search for inequality violations. For three exceptional cases — the graphs numbered 15,16,20 in HLP — we show that there exist non-Shannon-type entropic inequalities that imply these graphs are interesting.

Pilot-Wave Quantum Theory in Discrete Space and Time and the Principle of Least Action

Latest Results for Foundations of Physics

on 2016-6-27 12:00am GMT

Abstract

The idea of obtaining a pilot-wave quantum theory on a lattice with discrete time is presented. The motion of quantum particles is described by a $$|\Psi |^2$$ -distributed Markov chain. Stochastic matrices of the process are found by the discrete version of the least-action principle. Probability currents are the consequence of Hamilton’s principle and the stochasticity of the Markov process is minimized. As an example, stochastic motion of single particles in a double-slit experiment is examined.