# Weekly Papers on Quantum Foundations (27)

Self-testing of physical theories, or, is quantum theory optimal with respect to some information-processing task?. (arXiv:2003.00349v3 [quant-ph] UPDATED)

Self-testing usually refers to the task of taking a given set of observed correlations that are assumed to arise via a process that is accurately described by quantum theory, and trying to infer the quantum state and measurements. In other words it is concerned with the question of whether we can tell what quantum black-box devices are doing by looking only at their input-output behaviour and is known to be possible in several cases. Here we introduce a more general question: is it possible to self-test a theory, and, in particular, quantum theory? More precisely, we ask whether within a particular causal structure there are tasks that can only be performed in theories that have the same correlations as quantum mechanics in any scenario. We present a candidate task for such a correlation self-test and analyse it in a range of generalised probabilistic theories (GPTs), showing that none of these perform better than quantum theory. A generalisation of our results showing that all non-quantum GPTs are strictly inferior to quantum mechanics for this task would point to a new way to axiomatise quantum theory, and enable an experimental test that simultaneously rules out such GPTs.

Discovery of the Relativistic Schr\”odinger Equation. (arXiv:2012.12467v4 [physics.hist-ph] UPDATED)

We discuss the discovery of the relativistic wave equation for a spin-zero charged particle in the Coulomb field by Erwin Schr\”odinger (and elaborate on why he didn’t publish it).

Large violations in Kochen Specker contextuality and their applications. (arXiv:2106.15954v2 [quant-ph] UPDATED)

The Kochen-Specker (KS) theorem is a fundamental result in quantum foundations that has spawned massive interest since its inception. We present state-independent non-contextuality inequalities with large violations, in particular, we exploit a connection between Kochen-Specker proofs and pseudo-telepathy games to show KS proofs in Hilbert spaces of dimension $d \geq 2^{17}$ with the ratio of quantum value to classical bias being $O(\sqrt{d}/\log d)$. We study the properties of this KS set and show applications of the large violation. It has been recently shown that Kochen-Specker proofs always consist of substructures of state-dependent contextuality proofs called $01$-gadgets or bugs. We show a one-to-one connection between $01$-gadgets in $\mathbb{C}^d$ and Hardy paradoxes for the maximally entangled state in $\mathbb{C}^d \otimes \mathbb{C}^d$. We use this connection to construct large violation $01$-gadgets between arbitrary vectors in $\mathbb{C}^d$, as well as novel Hardy paradoxes for the maximally entangled state in $\mathbb{C}^d \otimes \mathbb{C}^d$, and give applications of these constructions. As a technical result, we show that the minimum dimension of the faithful orthogonal representation of a graph in $\mathbb{R}^d$ is not a graph monotone, a result that that may be of independent interest.

Testing Modified Gravity in Stimulated Photon-Photon Scattering — Dedicated to the late professor Yasunori Fujii. (arXiv:2107.00478v1 [gr-qc])

We propose a method to probe chameleon particles predicted in the $F(R)$ gravity as a model of the modified gravity based on the concept of a stimulated pulsed-radar collider. We analyze the chameleon mechanism induced by an ambient environment consisting of focused photon beams and a dilute gas surrounding a place where stimulated photon-photon scatterings occur. We then discuss how to extract the characteristic feature of the chameleon signal. We find that a chameleon with the varying mass around $(0.1-1)\,\mu$eV in a viable model of the $F(R)$ gravity is testable by searching for the steep pressure dependence of the 10th-power for the signal yield.

Initial Results from the LIGO Newtonian Calibrator. (arXiv:2107.00141v1 [gr-qc])

The precise calibration of the strain readout of the LIGO gravitational wave observatories is paramount to the accurate interpretation of gravitational wave events. This calibration is traditionally done by imparting a known force on the test masses of the observatory via radiation pressure. Here we describe the implementation of an alternative calibration scheme: the Newtonian Calibrator. This system uses a rotor consisting of both quadrupole and hexapole mass distributions to apply a time-varying gravitational force on one of the observatory’s test masses. The force produced by this rotor can be predicted to $<1\%$ relative uncertainty and is well-resolved in the readout of the observatory. This system currently acts as a cross-check of the existing absolute calibration system.

The Strong Emergence of Molecular Structure

Seifert, Vanessa A. (2020) The Strong Emergence of Molecular Structure. [Preprint]

The Local versus the Global in the History of Relativity: The Case of Belgium

ten Hagen, Sjang L. (2021) The Local versus the Global in the History of Relativity: The Case of Belgium. Science in Context, 33 (3). pp. 227-250.

Humeanism in light of quantum gravity

Abstract

Quantum Theory and Humeanism have long been thought to be incompatible due to the irreducibility of the correlations involved in entangled states. In this paper, we reconstruct the tension between Humeanism and entanglement via the concept of causal structure, and provide a philosophical introduction to the ER=EPR conjecture. With these tools, we then show how the concept of causal structure and the ER=EPR conjecture allow us to resolve the conflict between Humeanism and entanglement.

From structure preserving representation to making worlds with symbols

Fundamental non-qualitative properties

Abstract

The distinction between qualitative and non-qualitative properties should be familiar from discussions of the principle of the identity of indiscernibles: two otherwise exactly similar individuals, Castor and Pollux, might share all their qualitative properties yet differ with respect to their non-qualitative properties—for while Castor has the property being identical to Castor, Pollux does not. But while this distinction is familiar, there has not been much critical attention devoted to spelling out its precise nature. I argue that the class of non-qualitative properties is broader than it is often taken to be. When properly construed, it will not only include properties such as being identical to Castor, which somehow make reference to particular individuals, it will also include more general properties such as identity, composition, set membership, as well as various peculiarly ontological properties. Given that some of these more general properties help to explain objective similarity, we have reason to believe that there are fundamental non-qualitative properties.

Super-Humeanism and free will

Abstract

Super-Humeanism is an even more parsimonious ontology than Lewisian standard Humean metaphysics in that it rejects intrinsic properties (local qualties). There are point objects, but all there is to them are their relative positions (distance relations) and the change of them. Everything else supervenes on the Humean mosaic thus conceived. Hence, dynamical parameters (such as mass, charge, energy, a wave-function, etc.) come in on a par with the laws through their position in the best system. The paper sets out how Super-Humeanism has the conceptual means to reject van Inwagen’s consequence argument not by taking the laws to depend on us (as on standard Humean metaphysics), but by taking the initial values of the dynamical parameters that enter into the laws to be dependent on the motions that actually occur in the universe, including the motions of human bodies. The paper spells out the advantages of this proposal.

A dynamical systems approach to causation

Abstract

Our approach aims at accounting for causal claims in terms of how the physical states of the underlying dynamical system evolve with time. Causal claims assert connections between two sets of physicals states—their truth depends on whether the two sets in question are genuinely connected by time evolution such that physical states from one set evolve with time into the states of the other set. We demonstrate the virtues of our approach by showing how it is able to account for typical causes, causally relevant factors, being ‘the’ cause, and cases of overdetermination and causation by absences.

Entanglement and indistinguishability in a quantum ontology of properties

Fortin, Sebastian and Lombardi, Olimpia (2021) Entanglement and indistinguishability in a quantum ontology of properties. [Preprint]

Becoming Large, Becoming Infinite: The Anatomy of Thermal Physics and Phase Transitions in Finite Systems

Kuehn, Reimer and Lavis, David and Frigg, Roman (2021) Becoming Large, Becoming Infinite: The Anatomy of Thermal Physics and Phase Transitions in Finite Systems. [Preprint]

Better appreciating the scale of it (Lemaître and de Sitter at the BAAS Centenary)

De Baerdemaeker, Siska and Schneider, Mike D. (2021) Better appreciating the scale of it (Lemaître and de Sitter at the BAAS Centenary). [Preprint]

Modal Ω-Logic: Automata, Neo-Logicism, and Set-Theoretic Realism

Khudairi, Hasen (2019) Modal Ω-Logic: Automata, Neo-Logicism, and Set-Theoretic Realism. [Preprint]

On ‘Experiencing Time’ – a response to Simon Prosser

Deng, Natalja (2018) On ‘Experiencing Time’ – a response to Simon Prosser. Inquiry: an interdisciplinary journal of philosophy. ISSN 0020-174X

One thing after another: why the passage of time is not an illusion

Deng, Natalja (2019) One thing after another: why the passage of time is not an illusion. pp. 3-15.

Plenty to come: making sense of Correia’s and Rosenkranz’s growing block

Deng, Natalja (2021) Plenty to come: making sense of Correia’s and Rosenkranz’s growing block. [Preprint]

Violation of Bell Inequalities: Mapping the Conceptual Implications

Drummond, Brian (2021) Violation of Bell Inequalities: Mapping the Conceptual Implications. International Journal of Quantum Foundations, 7 (3). pp. 47-78.

Quantum advantage for computations with limited space

Nature Physics, Published online: 28 June 2021; doi:10.1038/s41567-021-01271-7

In general, it isn’t known when a quantum computer will have an advantage over a classical device. Now it’s proven that computers with limited working memory are more powerful if they are quantum.

Introducing Quantum Entanglement to First-Year Students: Resolving the Trilemma (arXiv:2106.12043 (physics))

Authors: W.M. Stuckey, Timothy McDevitt, Michael Silberstein

While quantum mechanics (QM) is covered at length in introductory physics textbooks, the concept of quantum entanglement is typically not covered at all, despite its importance in the rapidly growing area of quantum information science and its extensive experimental confirmation. Thus, physics educators are left to their own devices as to how to introduce this important concept. Regardless of how a physics educator chooses to introduce quantum entanglement, they face a trilemma involving its mysterious Bell-inequality-violating correlations. They can compromise on the the completeness of their introduction and simply choose not to share that fact. They can frustrate their more curious students by introducing the mystery and simply telling them that the QM formalism with its associated (equally mysterious) conservation law maps beautifully to the experiments, so there is nothing else that needs to be said. Or, they can compromise the rigor of their presentation and attempt to resolve the mystery by venturing into the metaphysical quagmire of competing QM interpretations. Herein, we resolve this trilemma in precisely the same way that Einstein resolved the mysteries of time dilation and length contraction that existed in the late nineteenth century. That is, we resort to “principle” explanation based on the mathematical consequences of “empirically discovered” facts. Indeed, our principle account of quantum entanglement is even based on the same principle Einstein used, i.e., the relativity principle or “no preferred reference frame.” Thus, this principle resolution of the trilemma is as complete, satisfying, analytically rigorous, and accessible as the standard introduction of special relativity for first-year physics students.