Weekly Papers on Quantum Foundations (47)

Crowther, Karen (2017) Inter-theory Relations in Quantum Gravity: Correspondence, Reduction, and Emergence. [Preprint]
Robertson, Douglas (2017) Brane Theory, Presentism and the “Now” Problem. [Preprint]

Author(s): Justin Dressel, Areeya Chantasri, Andrew N. Jordan, and Alexander N. Korotkov

We investigate the statistical arrow of time for a quantum system being monitored by a sequence of measurements. For a continuous qubit measurement example, we demonstrate that time-reversed evolution is always physically possible, provided that the measurement record is also negated. Despite this r…
[Phys. Rev. Lett. 119, 220507] Published Fri Dec 01, 2017

Authors: Antonio AcciolyWallace Herdy

The equivalence principle (EP), as well as Schiff’s conjecture, are discussed (en passant), and the connection between the EP and quantum mechanics is then briefly analyzed. Two semiclassical violations of the classical equivalence principle (CEP) but not of the weak one (WEP), i.e. Greenberger gravitational Bohr atom and the tree-level scattering of different quantum particles by an external weak higher-order gravitational field, are thoroughly investigated afterwards. Next, two quantum examples of systems that agree with the WEP but not with the CEP, namely COW experiment and free fall in a constant gravitational field of a massive object described by its wave-function $\Psi$, are discussed in detail. Keeping in mind that among the four examples focused on this work only COW experiment is based on an experimental test, some important details related to it, are presented as well.

Authors: Art Hobson

This paper reviews and suggests a resolution of the problem of definite outcomes of measurement. This problem, also known as “Schrodinger’s cat,” has long posed an apparent paradox because the state resulting from a measurement appears to be a quantum superposition in which the detector is in two macroscopically distinct states (alive and dead in the case of the cat) simultaneously. Many alternative interpretations of the quantum mathematical formalism, and several alternative modifications of the theory, have been proposed to resolve this problem, but no consensus has formed supporting any one of them. Applying standard quantum theory to the measurement state, together with the analysis and results of decades of nonlocality experiments with pairs of entangled systems, this paper shows the entangled measurement state is not a paradoxical macroscopic superposition of states. It is instead a phase-dependent superposition of correlations between states of the subsystems. Thus Schrodinger’s cat is a non-paradoxical “macroscopic correlation” in which one of the two correlated systems happens to be a detector. This insight resolves the problem of definite outcomes but it does not entirely resolve the measurement problem because the entangled state is still reversible.


This paper focuses on estimating real and quantum potentials from financial commodities. The log returns of six common commodities are considered. We find that some phenomena, such as the vertical potential walls and the time scale issue of the variation on returns, also exists in commodity markets. By comparing the quantum and classical potentials, we attempt to demonstrate that the information within these two types of potentials is different. We believe this empirical result is consistent with the theoretical assumption that quantum potentials (when embedded into social science contexts) may contain some social cognitive or market psychological information, while classical potentials mainly reflect ‘hard’ market conditions. We also compare the two potential forces and explore their relationship by simply estimating the Pearson correlation between them. The Medium or weak interaction effect may indicate that the cognitive system among traders may be affected by those ‘hard’ market conditions.


It is well known that the process of quantization—constructing a quantum theory out of a classical theory—is not in general a uniquely determined procedure. There are many inequivalent methods that lead to different choices for what to use as our quantum theory. In this paper, I show that by requiring a condition of continuity between classical and quantum physics, we constrain and inform the quantum theories that we end up with.


The long-lasting problem of proper mathematical representation of conjunctions and disjunctions in quantum logics is reviewed and three recent proposals of solutions are described.


Peter Mittelstaedt’s contributions to quantum logic and to the foundational problems of quantum theory have significantly realized the most authentic spirit of the International Quantum Structures Association: an original research about hard technical problems, which are often “entangled” with the emergence of important changes in our general world-conceptions. During a time where both the logical and the physical community often showed a skeptical attitude towards Birkhoff and von Neumann’s quantum logic, Mittelstaedt brought into light the deeply innovating features of a quantum logical thinking that allows us to overcome some strong and unrealistic assumptions of classical logical arguments. Later on his intense research on the unsharp approach to quantum theory and to the measurement problem stimulated the increasing interest for unsharp forms of quantum logic, creating a fruitful interaction between the work of quantum logicians and of many-valued logicians. Mittelstaedt’s general views about quantum logic and quantum theory seem to be inspired by a conjecture that is today more and more confirmed: there is something universal in the quantum theoretic formalism that goes beyond the limits of microphysics, giving rise to interesting applications to a number of different fields.


Recently the method based on irreducible representations of finite groups has been proposed as a tool for investigating the more sophisticated versions of Bell inequalities (V. Ugǔr Gűney, M. Hillery, Phys. Rev. A90, 062121 ([2014]) and Phys. Rev. A91, 052110 ([2015])). In the present paper an example based on the symmetry group S 4 is considered. The Bell inequality violation due to the symmetry properties of regular tetrahedron is described. A nonlocal game based on the inequalities derived is described and it is shown that the violation of Bell inequality implies that the quantum strategies outperform their classical counterparts.


Jean Perrins proof in the early 20th century of the reality of atoms and molecules is often taken as an exemplary form of robustness reasoning, where an empirical result receives validation if it is generated using multiple experimental approaches. In this paper, I describe in detail Perrins style of reasoning, and locate both qualitative and quantitative forms of argumentation. Particularly, I argue that his quantitative style of reasoning has mistakenly been viewed as a form of robustness reasoning, whereas I believe it is something different, what I call calibration. From this perspective, I re-evaluate recent interpretations of Perrin provided by Stathis Psillos, Peter Achinstein, Alan Chalmers, and Bas van Fraassen, all of whom read Perrin as a robustness reasoner, though not necessarily in the same sort of way. I then argue that by viewing Perrin as a calibration reasoner we gain a better understanding of why he believes himself to have established the reality of atoms and molecules. To conclude, I provide an alternative and more productive understanding of the basis of the dispute between realists and anti-realists.

Maxwell, Nicholas (2917) Could Inelastic Interactions Induce Quantum Probabilistic Transitions? [Preprint]
Fraser, James D. (2017) Renormalization and the Formulation of Scientific Realism. [Preprint]


By assuming a deterministic evolution of quantum systems and taking realism into account, we carefully build a hidden variable theory for Quantum Mechanics (QM) based on the notion of ontological states proposed by ’t Hooft (The cellular automaton interpretation of quantum mechanics, arXiv:1405.1548v3, 2015; Springer Open 185, https://doi.org/10.1007/978-3-319-41285-6, 2016). We view these ontological states as the ones embedded with realism and compare them to the (usual) quantum states that represent superpositions, viewing the latter as mere information of the system they describe. Such a deterministic model puts forward conditions for the applicability of Bell’s inequality: the usual inequality cannot be applied to the usual experiments. We build a Bell-like inequality that can be applied to the EPR scenario and show that this inequality is always satisfied by QM. In this way we show that QM can indeed have a local interpretation, and thus meet with the causal structure imposed by the Theory of Special Relativity in a satisfying way.

A 53-qubit quantum simulator is the biggest of its kind, and has already done some calculations that outperform most, if not all, classical computers

Probing many-body dynamics on a 51-atom quantum simulator

Nature 551, 7682 (2017). doi:10.1038/nature24622

Authors: Hannes Bernien, Sylvain Schwartz, Alexander Keesling, Harry Levine, Ahmed Omran, Hannes Pichler, Soonwon Choi, Alexander S. Zibrov, Manuel Endres, Markus Greiner, Vladan Vuletić & Mikhail D. Lukin

Controllable, coherent many-body systems can provide insights into the fundamental properties of quantum matter, enable the realization of new quantum phases and could ultimately lead to computational systems that outperform existing computers based on classical approaches. Here we demonstrate a method for creating controlled many-body

Niestegge, Gerd (2016) Quantum key distribution without the wavefunction. International Journal of Quantum Information, 15 (6).
Kallfelz, William (2015) Ontic Structural Realism and Natural Necessity. [Preprint]

Quantum physics dropwise

Quantum physics dropwise, Published online: 27 November 2017; doi:10.1038/s41567-017-0015-6

Classical wave-driven particles can mimic basic quantum properties, but how far this parallel extends is yet to be seen. Evidence for quantum-like mirages in a system of droplets moving on a fluid surface pushes the analogy into many-body territory.

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One Response

  1. Art Hobson
    Art Hobson at |

    I would love to have physicists’ feedback on my paper “Review and suggested resolution of the problem of Schrodinger’s cat,” listed above and published in the journal Contemporary Physics. It’s posted on arXiv. The paper shows that the entangled state of a superposed quantum system and its measuring apparatus is not a paradoxical superposition involving different states of the apparatus, but is merely a non-paradoxical superposition of correlations. This is just what we expect. This follows from simply studying the results of the theory and nonlocal experiments involving entangled photon pairs. Quantum theory and these experiments both imply that the entangled “measurement state” is not paradoxical, and they instruct is as to the true nature of this state.

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