# Weekly Papers on Quantum Foundations (32)

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.

Fluid Dynamics and Entropic Gravity. (arXiv:1608.00144v2 [hep-th] UPDATED)

on 2016-8-06 8:12am GMT

Authors: Ian Nagle

A new entropic gravity inspired derivation of general relativity from thermodynamics is presented. This generalizes, within Einstein gravity, the “Thermodynamics of Spacetime” approach by T. Jacobson, which relies on the Raychaudhuri evolution equation. Here the rest of the first law of thermodynamics is incorporated by using the Damour-Navier-Stokes equation, known from the membrane paradigm for describing fluid dynamics on the horizon.

Experimental Test of Bohr’s Complementarity Principle with Single Neutral Atom. (arXiv:1608.01450v1 [quant-ph])

on 2016-8-06 8:11am GMT

Bohr’s complementarity principle (BCP) is one of the cornerstones of quantum mechanics, and the counterintuitive behavior of wave-particle duality lies at its heart.BCP says that the properties of waves and particles for a quantum system cannot be simultaneously observed. Various tests of BCP with single photons have been performed.However, the low detection efficiency associated with fast-moving, massless photons makes the results less persuasive and more untenable. Here we use a well-controlled, massive, single trapped Cesium atom in a Ramsey interferometer to test BCP of wave-particle duality. A single atom is detected with much greater efficiency. Our results confirm the complementarity relation $P^2+V^2 \leqslant 1$, where $P^2$ and $V^2$ are the particle and wave behavior, respectively. We also deliberately introduce unbalance losses into our system and find the complementarity relation is formally “violated.” The whole experiment is closer to the classical notions, and the result is more ideal than ever, which makes BCP seem even more firm. Our observation provides an important complementation to understand the BCP of wave-particle duality. The system paves a way to observe selectively the wave-particle properties on a single quantum level for massive particles.

Quantum mechanics over sets: a pedagogical model with non-commutative finite probability theory as its quantum probability calculus

Latest Results for Synthese

on 2016-8-05 12:00am GMT

Abstract

This paper shows how the classical finite probability theory (with equiprobable outcomes) can be reinterpreted and recast as the quantum probability calculus of a pedagogical or toy model of quantum mechanics over sets (QM/sets). There have been several previous attempts to develop a quantum-like model with the base field of $${\mathbb {C}}$$ replaced by $${\mathbb {Z}}_{2}$$ . Since there are no inner products on vector spaces over finite fields, the problem is to define the Dirac brackets and the probability calculus. The previous attempts all required the brackets to take values in $${\mathbb {Z}}_{2}$$ . But the usual QM brackets $$\left\langle \psi |\varphi \right\rangle$$ give the “overlap” between states $$\psi$$ and $$\varphi$$ , so for subsets $$S,T\subseteq U$$ , the natural definition is $$\left\langle S|T\right\rangle =\left| S\cap T\right|$$ (taking values in the natural numbers). This allows QM/sets to be developed with a full probability calculus that turns out to be a non-commutative extension of classical Laplace-Boole finite probability theory. The pedagogical model is illustrated by giving simple treatments of the indeterminacy principle, the double-slit experiment, Bell’s Theorem, and identical particles in QM/Sets. A more technical appendix explains the mathematics behind carrying some vector space structures between QM over $${\mathbb {C}}$$ and QM/Sets over $${\mathbb {Z}}_{2}$$ .

The Limits of Physical Equivalence in Algebraic Quantum Field Theory

The British Journal for the Philosophy of Science – Advance Access

on 2016-8-04 5:06pm GMT

Some physicists and philosophers argue that unitarily inequivalent representations (UIRs) in quantum field theory (QFT) are mathematical surplus structure. Support for that view, sometimes called ‘algebraic imperialism’, relies on Fell’s theorem and its deployment in the algebraic approach to QFT. The algebraic imperialist uses Fell’s theorem to argue that UIRs are ‘physically equivalent’ to each other. The mathematical, conceptual, and dynamical aspects of Fell’s theorem will be examined. Its use as a criterion for physical equivalence is examined in detail and it is proven that Fell’s theorem does not apply to the vast number of representations used in the algebraic approach. UIRs are not another case of theoretical underdetermination, because they make different predictions about ‘classical’ operators. These results are applied to the Unruh effect where there is a continuum of UIRs to which Fell’s theorem does not apply.

• 1 Introduction
• 2 Weak Equivalence and Physical Equivalence
• 3 Mathematical Overview of Algebraic Quantum Field Theory
• 4 Fell’s Theorem and Philosophical Responses to Weak Equivalence
• 5 Weak Equivalence in C*-Algebras and W*-Algebras
• 6 Classical Equivalence and Weak Equivalence
• 7 Interlude: Is Weak Equivalence Really Physical Equivalence?
• 8 The Unruh Effect
• 9 Time Evolution and Symmetries
• 10 Conclusions
• Appendix

Ultraviolet cutoffs and the photon mass. (arXiv:1608.01214v1 [hep-th])

on 2016-8-04 1:15pm GMT

Authors: Piotr H. Chankowski (Warsaw U.), Adrian Lewandowski (Potsdam, Max Planck Inst. and Warsaw U.), Krzysztof A. Meissner(Warsaw U.)

The momentum UV cutoff in Quantum Field Theory is usually treated as an auxiliary device allowing to obtain finite amplitudes satisfying all physical requirements. It is even absent (not explicit) in the most popular approach – the dimensional regularization. We point out that the momentum cutoff treated as a bona fide physical scale, presumably equal or related to the Planck scale, would lead to unacceptable predictions. One of the dangers is a non-zero mass of the photon. In the naive approach, even with the cutoff equal to the Planck scale, this mass would grossly exceed the existing experimental bounds. We present the actual calculation using a concrete realization of the physical cutoff and speculate about the way to restore gauge symmetry order by order in the inverse powers of the cutoff scale.

A Direct Probe of the Evolutionary History of the Primordial Universe. (arXiv:1608.01299v1 [astro-ph.CO])

on 2016-8-04 1:14pm GMT

Since Hubble and Lamaitre’s discovery of the expanding universe using galaxies till the recent discovery of the accelerating universe using standard candles, direct measurements of the evolution of the scale factor of the universe a(t) have played central roles in establishing the standard model of cosmology. In this letter, we show that such a measurement may be extended to the primordial universe using massive fields as standard clocks, providing a direct evidence for the scenario responsible for the Big Bang. This is a short and non-technical introduction to the idea of classical and quantum primordial standard clocks.

Nonlinear Schr\”odinger equation from generalized exact uncertainty principle. (arXiv:1602.05004v2 [quant-ph] UPDATED)

on 2016-8-04 1:13pm GMT

Authors: Łukasz Rudnicki

Inspired by the generalized uncertainty principle (GUP), which adds gravitational effects to the standard description of quantum uncertainty, we extend the exact uncertainty principle (EUP) approach by Hall and Reginatto [J. Phys. A: Math. Gen. (2002) 35 3289], and obtain a (quasi)nonlinear Schr\”odinger equation. This quantum evolution equation of unusual form, enjoys several desired properties like separation of non-interacting subsystems or planewave solutions for free particles. Starting with the harmonic oscillator example, we show that every solution of this equation respects the gravitationally-induced minimal position uncertainty proportional to the Planck length. Quite surprisingly, our result successfully merges the core of classical physics with non-relativistic quantum mechanics in its extremal form. We predict that the commonly accepted phenomenon, namely a modification of a free-particle dispersion relation due to quantum gravity might not occur in reality.

Proceedings of the 2016 Workshop on Semantic Spaces at the Intersection of NLP, Physics and Cognitive Science. (arXiv:1608.01018v1 [cs.CL])

on 2016-8-04 1:13pm GMT

This volume contains the Proceedings of the 2016 Workshop on Semantic Spaces at the Intersection of NLP, Physics and Cognitive Science (SLPCS 2016), which was held on the 11th of June at the University of Strathclyde, Glasgow, and was co-located with Quantum Physics and Logic (QPL 2016). Exploiting the common ground provided by the concept of a vector space, the workshop brought together researchers working at the intersection of Natural Language Processing (NLP), cognitive science, and physics, offering them an appropriate forum for presenting their uniquely motivated work and ideas. The interplay between these three disciplines inspired theoretically motivated approaches to the understanding of how word meanings interact with each other in sentences and discourse, how diagrammatic reasoning depicts and simplifies this interaction, how language models are determined by input from the world, and how word and sentence meanings interact logically. This first edition of the workshop consisted of three invited talks from distinguished speakers (Hans Briegel, Peter G\”ardenfors, Dominic Widdows) and eight presentations of selected contributed papers. Each submission was refereed by at least three members of the Programme Committee, who delivered detailed and insightful comments and suggestions.

The logic of experimental tests, particularly of Everettian quantum theory

ScienceDirect Publication: Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics

on 2016-8-03 10:13pm GMT

Publication date: Available online 9 July 2016
Source:Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics
Author(s): David Deutsch
Claims that the standard procedure for testing scientific theories is inapplicable to Everettian quantum theory, and hence that the theory is untestable, are due to misconceptions about probability and about the logic of experimental testing. Refuting those claims by correcting those misconceptions leads to an improved theory of scientific methodology (based on Popper׳s) and testing, which allows various simplifications, notably the elimination of everything probabilistic from the methodology (‘Bayesian’ credences) and from fundamental physics (stochastic processes).

Atomic physics: A milestone in quantum computing

Nature Physical Sciences Research

on 2016-8-03 12:00am GMT

Quantum computers require many quantum bits to perform complex calculations, but devices with more than a few bits are difficult to program. A device based on five atomic quantum bits shows a way forward. See Letter p.63

Nature 536 35 doi: 10.1038/536035a

Quantum physics: Destruction of discrete charge

Nature Physical Sciences Research

on 2016-8-03 12:00am GMT

Electric charge is quantized in units of the electron’s charge. An experiment explores the suppression of charge quantization caused by quantum fluctuations and supports a long-standing theory that explains this behaviour. See Letter p.58

Nature 536 38 doi: 10.1038/536038a

QBism, FAPP and the Quantum Omelette. (Or, Unscrambling Ontological Problems from Epistemological Solutions in QM)

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

on 2016-8-02 9:47pm GMT

de Ronde, Christian (2016) QBism, FAPP and the Quantum Omelette. (Or, Unscrambling Ontological Problems from Epistemological Solutions in QM). [Preprint]

Approximations for the free evolution of self-gravitating quantum particles

PRA: Fundamental concepts

on 2016-8-01 2:00pm GMT

Author(s): André Großardt

The evolution of the center-of-mass wave function for a mesoscopic particle according to the Schrödinger-Newton equation can be approximated by a harmonic potential if the wave function is narrow compared to the size of the mesoscopic particle. It was noticed by Colin et al. [Phys. Rev. A 93, 06210…

[Phys. Rev. A 94, 022101] Published Mon Aug 01, 2016

Mapping curved spacetimes into Dirac spinors. (arXiv:1607.08732v1 [quant-ph])

on 2016-8-01 3:59am GMT

Authors: Carlos Sabín

We show how to transform a Dirac equation in curved spacetime into a Dirac equation in flat spacetime. In particular, we show that any solution of the free massless Dirac equation in a 1+1 dimensional flat spacetime can be transformed via a local phase transformation into a solution of the corresponding Dirac equation in a curved background, where the spacetime metric is encoded into the phase. In this way, the existing quantum simulators of the Dirac equation can naturally incorporate curved spacetimes. As a first example we use our technique to obtain solutions of the Dirac equation in a particular family of interesting spacetimes in 1+1 dimensions.

Bohr’s Relational Holism and the Classical-Quantum Interaction

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

on 2016-7-31 6:34pm GMT

Dorato, Mauro (2016) Bohr’s Relational Holism and the Classical-Quantum Interaction. [Preprint]

Niels Bohr and the Formalism of Quantum Mechanics

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

on 2016-7-31 6:31pm GMT

Dieks, Dennis (2016) Niels Bohr and the Formalism of Quantum Mechanics. [Preprint]