# Weekly Papers on Quantum Foundations (37)

Underground test of gravity-related wave function collapse

Nature Physics, Published online: 07 September 2020; doi:10.1038/s41567-020-1008-4The radiation emission rate from gravity-related wave function collapse is calculated and the results of a dedicated experiment at the Gran Sasso laboratory are reported, ruling out the natural parameter-free version of the Diósi–Penrose model.

A Local-Realistic Quantum Mechanical Model of Spin and Spin Entanglement. (arXiv:1901.00369v5 [quant-ph] UPDATED)

This paper aims at reproducing quantum mechanical (QM) spin and spin entanglement results using a realist, stochastic, and local approach, without the standard QM mathematical formulation. The concrete model proposed includes the description of Stern-Gerlach apparatuses and of Bell test experiments. Single particle trajectories are explicitly evaluated as a function of a few stochastic variables that they assumedly carry on. QM predictions re retrieved as probability distributions of similarly-prepared ensembles of particles. Notably, it is shown that the proposed model, despite being both local and realist, is able to violate the Bell–CHSH inequalities by exploiting the coincidence loophole and thus intrinsically renouncing to one of the Bell’s assumptions.Leggett-Garg tests for macrorealism: interference experiments and the simple harmonic oscillator. (arXiv:2009.03856v2 [quant-ph] UPDATED)

Leggett-Garg (LG) tests for macrorealism were originally designed to explore quantum coherence on the macroscopic scale. Interference experiments and systems modelled by harmonic oscillators provide useful examples of situations in which macroscopicity has been approached experimentally and may be turned into LG tests with a dichotomic variable Q by simple partitionings of a continuous variable such as position. Applying this approach to the double-slit experiment in which a measurement at the slits and screen are considered, we find that LG violations are always accompanied by destructive interference. The converse is not true in general and we find that there are non-trivial regimes in which there is destructive interference but the two-time LG inequalities are satisfied which implies that it is in fact often possible to assign (indirectly determined) probabilities for the interferometer paths. Similar features have been observed in recent work involving a LG analysis of a Mach-Zehnder interferometer and we compare with those results. We also compare with the related problem in which a more direct determination of the paths is carried out using a variable-strength measurement at the slits and the resulting deterioration of the interference pattern is examined. We extend the analysis to the triple-slit experiment. We find examples of some surprising relationships between LG inequalities and NSIT conditions that do not exist for dichotomic variables, including a violation of the Luders bound. We analyse a two-time LG inequality for the simple harmonic oscillator. We find an analytically tractable example showing a two-time LG violation with a gaussian initial state, echoing recent results of Bose et al (Phys. Rev. Lett. 120, 210402 (2018)).The Beginning of the Nuclear Age. (arXiv:2009.05001v1 [physics.hist-ph])

Authors: M. Shifman

The article below is based on lectures delivered to new students remotely in the course of orientation. It presents the quantum theory tree from its inception a century ago till today. The main focus is on the nuclear physics – HEP branch.The philosophical underpinning of the absorber theory of radiation

Publication date: Available online 9 September 2020

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

Publication date: Available online 8 September 2020

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

Author(s): Siska De Baerdemaeker, Nora Mills BoydJosephson AC effect induced by weak gravitational field. (arXiv:2009.04967v1 [gr-qc])

In this paper we examine the possibility of a Josephson AC effect between two superconductors induced by the Earth’s gravitational field, making use of the gravito-Maxwell formalism. The theoretical framework exploits the symmetry between the weak field expansion of the gravitational field and the standard Maxwell formulation, combined with the Josephson junction physics. We also suggest a suitable experimental setup, analysing also the related possible difficulties in measurements.Quantum entanglement and the non-orientability of spacetime. (arXiv:2009.04990v1 [hep-th])

Authors: Ovidiu Racorean

We argue, in the context of Ads/CFT correspondence, that the degree of entanglement on the CFTs side determines the orientation of space and time on the dual global spacetime. That is, the global spacetime dual to entangled copies of field theory is non-orientable, while the product state of the CFTs results in an orientable spacetime. As a result, disentangling the degrees of freedom between two copies of CFT implies, on the gravity side, the transition from a non-orientable spacetime to a spacetime having a definite orientation of space and time, thus an orientable spacetime. We conclude showing that topology change induced by decreasing the entanglement between two sets of degrees of freedom corresponds to a topological blow down operation.The End of a Black Hole’s Evaporation — Part I. (arXiv:2009.05016v1 [gr-qc])

At the end of Hawking evaporation, the horizon of a black hole enters a physical region where quantum gravity cannot be neglected. The physics of this region has not been much explored. We characterise its physics and introduce a technique to study it.Generalized uncertainty principle in resonant detectors of gravitational waves. (arXiv:2005.09454v2 [gr-qc] UPDATED)

With the direct detection of gravitational waves by advanced LIGO detector, a new “window” to quantum gravity phenomenology has been opened. At present, these detectors achieve the sensitivity to detect the length variation ($\delta L$), $\mathcal{O} \approx 10^{-17}-10^{-21}$ meter. Recently a more stringent upperbound on the dimensionless parameter $\beta_0$, bearing the effect of generalized uncertainty principle has been given which corresponds to the intermediate length scale $l_{im}= \sqrt{\beta_0} l_{pl} \sim 10^{-23} m$. Hence the flavour of the generalized uncertainty principle can be realised by observing the response of the vibrations of phonon modes in such resonant detectors in the near future. In this paper, therefore, we calculate the resonant frequencies and transition rates induced by the incoming gravitational waves on these detectors in the generalized uncertainty principle framework. It is observed that the effects of the generalized uncertainty principle bears its signature in both the time independent and dependent part of the gravitational wave-harmonic oscillator Hamiltonian. We also make an upper bound estimate of the GUP parameter.What Have Google’s Random Quantum Circuit Simulation Experiments Demonstrated about Quantum Supremacy?

Horner, Jack K. and Symons, John (2020) What Have Google’s Random Quantum Circuit Simulation Experiments Demonstrated about Quantum Supremacy? [Preprint]Why the Many-Worlds Interpretation of quantum mechanics needs more than Hilbert space structure

Hemmo, Meir and Shenker, Orly (2020) Why the Many-Worlds Interpretation of quantum mechanics needs more than Hilbert space structure. Scientific Challenges to Common Sense Philosophy. pp. 61-70. ISSN 9781138479982Cartography of the space of theories: an interpretational chart for fields that are both (dark) matter and spacetime

Martens, Niels C.M. and Lehmkuhl, Dennis (2020) Cartography of the space of theories: an interpretational chart for fields that are both (dark) matter and spacetime. Studies in History and Philosophy of Modern Physics. ISSN 1355-2198Dark Matter = Modified Gravity? Scrutinising the spacetime–matter distinction through the modified gravity/ dark matter lens

Martens, Niels C.M. and Lehmkuhl, Dennis (2020) Dark Matter = Modified Gravity? Scrutinising the spacetime–matter distinction through the modified gravity/ dark matter lens. Studies in History and Philosophy of Modern Physics. ISSN 1355-2198Classical Particle Indistinguishability, Precisely

Wills, James (2020) Classical Particle Indistinguishability, Precisely. [Preprint]One time, two times, or no time?

Wuthrich, Christian (2020) One time, two times, or no time? [Preprint]Out of Nowhere: The emergence of spacetime from causal sets

Wuthrich, Christian and Huggett, Nick (2020) Out of Nowhere: The emergence of spacetime from causal sets. [Preprint]

Other minds are neither seen nor inferred

### Abstract

How do we know about other minds on the basis of perception? The two most common answers to this question are that we literally perceive others’ mental states, or that we infer their mental states on the basis of perceiving something else. In this paper, I argue for a different answer. On my view, we don’t perceive mental states, and yet perceptual experiences often immediately justify mental state attributions. In a slogan: other minds are neither seen nor inferred. I argue that this view offers the best explanation of our deeply equivocal intuitions about perception-based mental state attributions, and also holds substantial interest for the epistemology of perception more generally.