# Weekly Papers on Quantum Foundations (38)

On possible explanations for quantum contextuality. (arXiv:2109.07636v1 [quant-ph])

Recent research on quantum contextuality has been strongly centered on device-independent frameworks, such as the many graph approaches to contextuality and the celebrated sheaf-theoretical approach. Contextuality is described in these frameworks as a property of data only, making it possible to characterize and quantify the phenomena regardless of the reasons why it occurs. In this paper we look beyond the data and focus on possible explanations for this experimental fact. We show that a classical system generating contextual data can easily be found if the following conditions are satisfied (1) We only have access to a specific collection of “epistemic” measurements (which, all things considered, is basically Bohr’s view on quantum measurements) and (2) There is a limitation on which of these measurements can be jointly performed. The way we see it, this example indicates that contextuality may be a consequence of the type of measurement taken into account, instead of an intrinsic feature of the system upon which these measurements are performed; if this is correct, the widespread idea that quantum contextuality is a non-classical feature can be avoided.

On idealism of Anton Zeilinger’s information interpretation of quantum mechanics. (arXiv:2109.07811v1 [quant-ph])

We argue that Anton Zeilinger’s “foundational conceptual principle” for quantum mechanics according to which an elementary system carries one bit of information is an idealistic principle, which should be replaced by a realistic principle of contextuality. Specific properties of quantum systems are a consequence of impossibility to speak about them without reference to the tools of their observation/identification and, consequently, context in which these tools are applied.

Leggett-Garg tests for macrorealism in the quantum harmonic oscillator and more general bound systems. (arXiv:2109.03118v2 [quant-ph] UPDATED)

Macrorealism (MR) is the world-view that at all moments of time, a system is definitely in one of the observable states available to it, irrespective of past or future measurements. The Leggett-Garg (LG) inequalities were introduced to test MR and assess for the presence of macroscopic quantum coherence. Since such effects could plausibly be found in various types of macroscopic oscillators, we apply the LG approach to the quantum harmonic oscillator (QHO) and more general bound systems, using a single dichotomic variable Q given by the sign of the oscillator position. We present a simple method to calculate the relevant temporal correlators for any bound system for which the energy eigenspectrum is (exactly or numerically) known. We then apply this result to the QHO for a variety of experimentally accessible states, namely energy eigenstates, and superpositions thereof. For the subspace of states spanned by only the ground state and first excited state, we readily find substantial regions of parameter space in which the two and three-time LG inequalities can each be independently violated or satisfied. We find violations persist (although are reduced) when the sign function defining Q is smeared to reflect experimental imprecision. We also find that LG violations diminish at high energies, showing the expected classicalization. With a Q defined as an arbitrary position coarse graining, we find two-time LG violations even in the ground state, a simple example of a feature recently noted by Bose et al. [Phys. Rev. Lett. 120, 210402 (2018)]. We also show that two-time LG violations in a gaussian state are readily found if the dichotomic variable at one of the times is taken to be the parity operator. To demonstrate the versatility of the technique we developed, we perform an LG analysis for the Morse potential, where we find significant violations for the first excited state.

Constraints on Quantum Gravity and the Photon Mass from Gamma Ray Bursts. (arXiv:2109.07850v1 [gr-qc])

Lorentz Invariance Violation in Quantum Gravity (QG) models or a non-zero photon mass, $m_\gamma$, would lead to an energy-dependent propagation speed for photons, such that photons of different energies from a distant source would arrive at different times, even if they were emitted simultaneously. By developing source-by-source, Monte Carlo-based forward models for such time delays from Gamma Ray Bursts, and marginalising over empirical noise models describing other contributions to the time delay, we derive constraints on $m_\gamma$ and the QG length scale, $\ell_{\rm QG}$, using spectral lag data from the BATSE satellite. We find $m_\gamma < 4.0 \times 10^{-5} \, h \, {\rm eV}/c^2$ and $\ell_{\rm QG} < 5.3 \times 10^{-18} \, h \, {\rm \, GeV^{-1}}$ at 95% confidence, and demonstrate that these constraints are robust to the choice of noise model. The QG constraint is among the tightest from studies which consider multiple Gamma Ray Bursts and the constraint on $m_\gamma$, although weaker than from using radio data, provides an independent constraint which is less sensitive to the effects of dispersion by electrons.

Comment on “Maximum force and cosmic censorship”. (arXiv:2109.07700v1 [gr-qc])

Authors: Christoph Schiller

Despite suggestions to the contrary, no counterargument to the principle of maximum force or to the equivalent principle of maximum power has yet been provided.

Can the Hubble tension be resolved by bulk viscosity?. (arXiv:2107.13533v2 [gr-qc] UPDATED)

Authors: Ben David NormannIver Håkon Brevik

We show that the cosmic bulk viscosity estimated in our previous works is sufficient to bridge the $H_0$ value inferred from observations of the early universe with the value inferred from the local (late) universe.

A computational complexity approach to the definition of empirical equivalence.

Brogioli, Doriano (2019) A computational complexity approach to the definition of empirical equivalence. [Preprint]

Two Quantum Logics of Indeterminacy

Fletcher, Samuel C. and Taylor, David E. (2021) Two Quantum Logics of Indeterminacy. Synthese. ISSN 1573-0964

Can Redescriptions of Outcomes Salvage the Axioms of Decision Theory?

Baccelli, Jean and Mongin, Philippe (2021) Can Redescriptions of Outcomes Salvage the Axioms of Decision Theory? Philosophical Studies. ISSN 0031-8116

Maxwell’s Demon in Quantum Mechanics

Hemmo, Meir and Shenker, Orly R. (2020) Maxwell’s Demon in Quantum Mechanics. Entropy, 22. p. 269. ISSN 1099-4300

Macroscopically Nonlocal Quantum Correlations

Author(s): Miguel Gallego and Borivoje Dakić

It is usually believed that coarse graining of quantum correlations leads to classical correlations in the macroscopic limit. Such a principle, known as macroscopic locality, has been proved for correlations arising from independent and identically distributed (IID) entangled pairs. In this Letter, …

[Phys. Rev. Lett. 127, 120401] Published Thu Sep 16, 2021

Consciousness, Phenomenal Consciousness, and Free Will

Sytsma, Justin and Snater, Melissa (2021) Consciousness, Phenomenal Consciousness, and Free Will. [Preprint]

We Cannot Allow a Wikipedia Gap!

Ross, Sage Rogers (2007) We Cannot Allow a Wikipedia Gap! Spontaneous Generations: A Journal for the History and Philosophy of Science, 1 (1). ISSN 1913-0465