# Weekly Papers on Quantum Foundations (44)

How do I introduce Schr\”odinger equation during the quantum mechanics course?. (arXiv:2010.15589v1 [physics.ed-ph])

In this paper I explain how I usually introduce the Schr\”odinger equation during the quantum mechanics course. My preferred method is the chronological one. Since the Schr\”odinger equation belongs to a special case of wave equations I start the course with introducing the wave equation. The Schr\”odinger equation is derived with the help of the two quantum concepts introduced by Max Planck, Einstein, and de Broglie, i.e., the energy of a photon $E=\hbar\omega$ and the wavelength of the de Broglie wave $\lambda=h/p$. Finally, the difference between the classical wave equation and the quantum Schr\”odinger one is explained in order to help the students to grasp the meaning of quantum wavefunction $\Psi({\bf r},t)$. A comparison of the present method to the approaches given by the authors of quantum mechanics textbooks as well as that of the original Nuffield A level is presented. It is found that the present approach is different from those given by these authors, except by Weinberg or Dicke and Wittke. However, the approach is in line with the original Nuffield A level one.

Multipath Wave Particle Duality with a Spooky Path Detector. (arXiv:2010.15719v1 [quant-ph])

According to Bohr’s principle of complementarity, a quanton can behave either as a wave or a particle, depending on the choice of the experimental setup. Some recent two-path interference experiments have devised methods where one can have a quantum superposition of the two choices, thus indicating that a quanton may be in a superposition of wave and particle nature. These experiments have been of interest from the point of view of Wheeler’s delayed-choice experiment. However, it has also been claimed that this experiment can violate complementarity. Here we theoretically analyze a multipath interference experiment that has a which-path detector in a quantum superposition of being present and absent. We show that a tight multipath wave-particle duality relation is respected in all such situations, and complementarity holds good. The apparent violation of complementarity may be due to incorrect evaluation of path distinguishability in such scenarios.

Relational analysis of the Frauchiger–Renner paradox and interaction-free detection of records from the past. (arXiv:1902.07139v3 [quant-ph] UPDATED)

We present an analysis of the Frauchiger–Renner Gedankenexperiment from the point of view of the relational interpretation of quantum mechanics. Our analysis indicates that the paradox obtained by Frauchiger and Renner arises from reasoning about other agent’s knowledge in the past without validation by surviving records. A by-product of our analysis is an interaction-free detection scheme for the existence of records from the past.

Historical Context, Scientific Context, and Translation of Haidinger’s (1844) Discovery of Naked-Eye Visibility of the Polarization of Light. (arXiv:2010.15252v1 [physics.hist-ph])

Authors: Robert P. O’Shea (1), Shelby E. Temple (2,3), Gary P. Misson (4,5), Nicholas J. Wade (6), Michael Bach (7,8) ((1) Institute of Psychology–Wilhelm Wundt, University of Leipzig, Leipzig Germany, (2) School of Biological Sciences, University of Bristol, Bristol, UK, (3) Azul Optics Ltd, Bristol, UK, (4) School of Life & Health Sciences, Aston University, Birmingham, UK, (5) Department of Ophthalmology, South Warwickshire NHS Foundation Trust, Warwick, UK, (6) Psychology, University of Dundee, Dundee, UK, (7) University Eye Center, Medical Center, University of Freiburg, Freiburg, Germany, (8) Faculty of Medicine, University of Freiburg, Freiburg, Germany)

In 1844, the Austrian mineralogist Wilhelm von Haidinger reported he could see the polarization of light with the naked eye. It appears as a faint, blurry, transient, yellow hourglass shape superimposed on whatever one looks at. It is now commonly called Haidinger’s brushes. To our surprise, even though the paper is well cited, we were unable to find a translation of it from its difficult, nineteenth-century German into English. We provide one, with annotations to set the paper into its scientific and historical context.

Gravitational-wave research as an emerging field in the Max Planck Society. The long roots of GEO600 and of the Albert Einstein Institute. (arXiv:2003.00941v2 [gr-qc] UPDATED)

Authors: Luisa BonolisJuan-Andres Leon

On the occasion of the 50th anniversary since the beginning of the search for gravitational waves at the Max Planck Society, and in coincidence with the 25th anniversary of the foundation of the Albert Einstein Institute, we explore the interplay between the renaissance of general relativity and the advent of relativistic astrophysics following the German early involvement in gravitational-wave research, to the point when gravitational-wave detection became established by the appearance of full-scale detectors and international collaborations. On the background of the spectacular astrophysical discoveries of the 1960s and the growing role of relativistic astrophysics, Ludwig Biermann and his collaborators at the Max Planck Institute for Astrophysics in Munich became deeply involved in research related to such new horizons. At the end of the 1960s, Joseph Weber’s announcements claiming detection of gravitational waves sparked the decisive entry of this group into the field, in parallel with the appointment of the renowned relativist Juergen Ehlers. The Munich area group of Max Planck institutes provided the fertile ground for acquiring a leading position in the 1970s, facilitating the experimental transition from resonant bars towards laser interferometry and its innovation at increasingly large scales, eventually moving to a dedicated site in Hannover in the early 1990s. The Hannover group emphasized perfecting experimental systems at pilot scales, and never developed a full-sized detector, rather joining the LIGO Scientific Collaboration at the end of the century. In parallel, the Max Planck Institute for Gravitational Physics (Albert Einstein Institute) had been founded in Potsdam, and both sites, in Hannover and Potsdam, became a unified entity in the early 2000s and were central contributors to the first detection of gravitational waves in 2015.

Testing Gravity on Cosmic Scales: A Case Study of Jordan-Brans-Dicke Theory. (arXiv:2010.15278v1 [astro-ph.CO])

We provide an end-to-end exploration of a distinct modified gravitational theory in Jordan-Brans-Dicke (JBD) gravity, from an analytical and numerical description of the background expansion and linear perturbations, to the nonlinear regime captured with a hybrid suite of $N$-body simulations, to the parameter constraints from existing cosmological probes. The nonlinear corrections to the matter power spectrum due to baryons, massive neutrinos, and modified gravity are simultaneously modeled and propagated in the cosmological analysis for the first time. In the combined analysis of the Planck CMB temperature, polarization, and lensing reconstruction, Pantheon supernova distances, BOSS measurements of BAO distances, the Alcock-Paczynski effect, and the growth rate, along with the joint ($3\times2$pt) dataset of cosmic shear, galaxy-galaxy lensing, and overlapping redshift-space galaxy clustering from KiDS and 2dFLenS, we constrain the JBD coupling constant, $\omega_{\rm BD}>1540$ (95% CL), the effective gravitational constant, $G_{\rm matter}/G=0.997\pm0.029$, the sum of neutrino masses, $\sum m_{\nu}<0.12$ eV (95% CL), and the baryonic feedback amplitude, $B<2.8$ (95% CL), all in agreement with the standard model expectation. We show that the uncertainty in the gravitational theory alleviates the tension between KiDS$\times$2dFLenS and Planck to below $1\sigma$ and the tension in the Hubble constant between Planck and the direct measurement of Riess et al. (2019) down to ~$3\sigma$; however, we find no substantial model selection preference for JBD gravity relative to $\Lambda$CDM. We further show that the neutrino mass bound degrades by up to a factor of $3$ as the $\omega_{\rm BD}$ parameterization becomes more restrictive, and that a positive shift in $G_{\rm matter}/G$ suppresses the CMB damping tail in a way that might complicate future inferences of small-scale physics. (Abridged)

Book Review: French, S., & Saatsi, J. (Eds.). (2020). Scientific Realism and the Quantum. Oxford University Press

Glick, David (2020) Book Review: French, S., & Saatsi, J. (Eds.). (2020). Scientific Realism and the Quantum. Oxford University Press. [Preprint]

Two Constants in Carnap’s View on Scientific Theories

Lutz, Sebastian (2020) Two Constants in Carnap’s View on Scientific Theories. [Preprint]

Clock comparison using black holes

Nature Physics, Published online: 29 October 2020; doi:10.1038/s41567-020-01071-5

Observing accreting black holes in the early Universe allows precise comparison of clocks over intercontinental distances on Earth. This is achieved with a novel observation strategy using the next generation of very long baseline interferometry systems.

Measurement of Identical Particle Entanglement and the Influence of Antisymmetrization

Author(s): J. H. Becher, E. Sindici, R. Klemt, S. Jochim, A. J. Daley, and P. M. Preiss

We explore the relationship between symmetrization and entanglement through measurements on few-particle systems in a multiwell potential. In particular, considering two or three trapped atoms, we measure and distinguish correlations arising from two different physical origins: antisymmetrization of…

[Phys. Rev. Lett. 125, 180402] Published Wed Oct 28, 2020

Euler’s Königsberg: the explanatory power of mathematics

Räz, Tim (2017) Euler’s Königsberg: the explanatory power of mathematics. European Journal for Philosophy of Science. ISSN 1879-4912

Stability in Cosmology, from Einstein to Inflation

McCoy, C.D. (2020) Stability in Cosmology, from Einstein to Inflation. Thinking About Space and Time. pp. 71-89.

New powers for Dispositionalism

Abstract

Establishing Dispositionalism as a viable theory of modality requires the successful fulfilment of two tasks: (i) showing that all modal truths can be derived from truths about actual powers, and (ii) offering a suitable metaphysics of powers. These two tasks are intertwined: difficulties in one can affect the chances of success in the other. In this paper, I generalise an objection to Dispositionalism by Jessica Leech and argue that the theory in its present form is ill-suited to account for de re truths about merely possible entities. I argue that such difficulty is rooted in a problem in the metaphysics of powers. In particular, I contend that the well-known tension between two key principle of powers ontology, namely Directedness (all powers are “for” their manifestation) and Independence (some powers might fail to bring about their manifestation) has received an unsatisfactory solution so far, and that it is this unsatisfactory solution concerning the status of “unmanifested manifestations” that makes it hard for Dispositionalism to account for mere possibilia. I develop a novel account of the status of unmanifested manifestations and an overall metaphysics of powers which allows to better respond to Leech’s objection and handle mere possibilia. The central idea of the proposal is that unmanifested manifestations are akin to mere logical existents, and are best characterised as non-essentially non-located entities.

The Math is not the Territory: Navigating the Free Energy Principle

Andrews, Mel (2020) The Math is not the Territory: Navigating the Free Energy Principle. [Preprint]

Quantum probability’s algebraic origin

Niestegge, Gerd (2020) Quantum probability’s algebraic origin. Entropy 2020, 22, 1196. ISSN 1099-4300

The Heisenberg limit for laser coherence

Nature Physics, Published online: 26 October 2020; doi:10.1038/s41567-020-01049-3

The coherence of a close-to-ideal laser beam can be quadratically better than what was believed to be the quantum limit. This new Heisenberg limit could be attained with circuit quantum electrodynamics.

Bell’s Theorem, Quantum Probabilities, and Superdeterminism

Chen, Eddy Keming (2020) Bell’s Theorem, Quantum Probabilities, and Superdeterminism. [Preprint]

Opinion: Why science needs philosophy

Laplane, Lucie and Mantovani, Paolo and Adolphs, Ralph and Chang, Hasok and Mantovani, Alberto and McFall-Ngai, Margaret and Rovelli, Carlo and Sober, Elliott and Pradeu, Thomas (2019) Opinion: Why science needs philosophy. Proceedings of the National Academy of Sciences, 116 (10). pp. 3948-3952. ISSN 0027-8424