# Weekly Papers on Quantum Foundations (15)

Quantum Entanglement Undermines Structural Realism

Park, Seungbae (2021) Quantum Entanglement Undermines Structural Realism. Metaphysica.

How Artworks Modify our Perception of the World

Vernazzani, Alfredo (2021) How Artworks Modify our Perception of the World. [Preprint]

Geometry of Faithful Entanglement

Author(s): Otfried Gühne, Yuanyuan Mao, and Xiao-Dong Yu

A typical concept in quantum state analysis is based on the idea that states in the vicinity of some pure entangled state share the same properties, implying that states with a high fidelity must be entangled. States whose entanglement can be detected in this way are also called faithful. We prove a…

[Phys. Rev. Lett. 126, 140503] Published Fri Apr 09, 2021

Detecting Many-Body Bell Nonlocality by Solving Ising Models

Author(s): Irénée Frérot and Tommaso Roscilde

Bell nonlocality represents the ultimate consequence of quantum entanglement, fundamentally undermining the classical tenet that spatially separated degrees of freedom possess objective attributes independently of the act of their measurement. Despite its importance, probing Bell nonlocality in many…

[Phys. Rev. Lett. 126, 140504] Published Fri Apr 09, 2021

A tale of two kinds of exceptional point in a hydrogen molecule. (arXiv:2104.03383v1 [quant-ph])

We study the parity and time-reversal ($\mathcal{PT}$) symmetric quantum physics in a non-Hermitian non-relativistic hydrogen molecule with local (Hubbard type) Coulomb interaction. We consider non-Hermiticity generated from both kinetic and orbital energies of the atoms and encounter the existence of two different types of exceptional points (EPs) in pairs. These two kinds of EP are characteristically different and depend differently on the interaction strength. Our discovery may open the gates of a rich physics emerging out of a simple Hamiltonian resembling a two-site Hubbard model.

Do Bloch waves interfere with one another ?. (arXiv:2104.03622v1 [quant-ph])

Here we show that two Bloch states, which are energy eigenstates of a quantum periodic potential problem, with different wavevectors can not be linearly superposed to display quantum interference of any kind that captures the relative phase between them. This is due to the existence of a superselection rule in these systems, whose origin lies in the discrete translation symmetry. A topological reason leading to such a superselection is found. A temporal analogue of this superselection rule in periodically driven quantum systems is also uncovered, which forbids the coherent superposition of any two quasi-periodic Floquet states with different quasienergies.

Measurement of the Casimir Force between 0.2 and 8 mum: Experimental Procedures and Comparison with Theory. (arXiv:2104.03857v1 [quant-ph])

We present results on the determination of the differential Casimir force between an Au-coated sapphire sphere and the top and bottom of Au-coated deep silicon trenches performed by means of the micromechanical torsional oscillator in the range of separations from 0.2 to 8 $\upmu$m. The random and systematic errors in the measured force signal are determined at the 95\% confidence level and combined into the total experimental error. The role of surface roughness and edge effects is investigated and shown to be negligibly small. The distribution of patch potentials is characterized by Kelvin probe microscopy, yielding an estimate of the typical size of patches, the respective r.m.s. voltage and their impact on the measured force. A comparison between the experimental results and theory is performed with no fitting parameters. For this purpose, the Casimir force in the sphere-plate geometry is computed independently on the basis of first principles of quantum electrodynamics using the scattering theory and the gradient expansion. In doing so, the frequency-dependent dielectric permittivity of Au is found from the optical data extrapolated to zero frequency by means of the plasma and Drude models. It is shown that the measurement results exclude the Drude model extrapolation over the region of separations from 0.2 to 4.8~$\upmu$m, whereas the alternative extrapolation by means of the plasma model is experimentally consistent over the entire measurement range. A discussion of the obtained results is provided.

Quantum Zeno effect generalized. (arXiv:1901.09393v3 [math-ph] UPDATED)

The quantum Zeno effect, in its original form, uses frequent projective measurements to freeze the evolution of a quantum system that is initially governed by a fixed Hamiltonian. We generalize this effect simultaneously in three directions by allowing open system dynamics, time-dependent evolution equations and general quantum operations in place of projective measurements. More precisely, we study Markovian master equations with bounded generators whose time dependence is Lipschitz continuous. Under a spectral gap condition on the quantum operation, we show how frequent measurements again freeze the evolution outside an invariant subspace. Inside this space the evolution is described by a modified master equation.

Fluctuation theorems from Bayesian retrodiction. (arXiv:2009.02849v4 [quant-ph] UPDATED)

Quantitative studies of irreversibility in statistical mechanics often involve the consideration of a reverse process, whose definition has been the object of many discussions, in particular for quantum mechanical systems. Here we show that the reverse channel very naturally arises from Bayesian retrodiction, both in classical and quantum theories. Previous paradigmatic results, such as Jarzynski’s equality, Crooks’ fluctuation theorem, and Tasaki’s two-measurement fluctuation theorem for closed driven quantum systems, are all shown to be consistent with retrodictive arguments. Also, various corrections that were introduced to deal with nonequilibrium steady states or open quantum systems are justified on general grounds as remnants of Bayesian retrodiction. More generally, with the reverse process constructed on consistent logical inference, fluctuation relations acquire a much broader form and scope.

The Trouble with “Puddle Thinking”: A User’s Guide to the Anthropic Principle. (arXiv:2104.03381v1 [physics.hist-ph])

Authors: Geraint F. LewisLuke A. Barnes

Are some cosmologists trying to return human beings to the centre of the cosmos? In the view of some critics, the so-called “anthropic principle” is a desperate attempt to salvage a scrap of dignity for our species after a few centuries of demotion at the hands of science. It is all things archaic and backwards – teleology, theology, religion, anthropocentrism – trying to sneak back in scientific camouflage. We argue that this is a mistake. The anthropic principle is not mere human arrogance, nor is it religion in disguise. It is a necessary part of the science of the universe.

The Autodidactic Universe. (arXiv:2104.03902v1 [hep-th])

We present an approach to cosmology in which the Universe learns its own physical laws. It does so by exploring a landscape of possible laws, which we express as a certain class of matrix models. We discover maps that put each of these matrix models in correspondence with both a gauge/gravity theory and a mathematical model of a learning machine, such as a deep recurrent, cyclic neural network. This establishes a correspondence between each solution of the physical theory and a run of a neural network. This correspondence is not an equivalence, partly because gauge theories emerge from $N \rightarrow \infty$ limits of the matrix models, whereas the same limits of the neural networks used here are not well-defined. We discuss in detail what it means to say that learning takes place in autodidactic systems, where there is no supervision. We propose that if the neural network model can be said to learn without supervision, the same can be said for the corresponding physical theory. We consider other protocols for autodidactic physical systems, such as optimization of graph variety, subset-replication using self-attention and look-ahead, geometrogenesis guided by reinforcement learning, structural learning using renormalization group techniques, and extensions. These protocols together provide a number of directions in which to explore the origin of physical laws based on putting machine learning architectures in correspondence with physical theories.

Machine-Learning Mathematical Structures. (arXiv:2101.06317v2 [cs.LG] UPDATED)

Authors: Yang-Hui He

We review, for a general audience, a variety of recent experiments on extracting structure from machine-learning mathematical data that have been compiled over the years. Focusing on supervised machine-learning on labeled data from different fields ranging from geometry to representation theory, from combinatorics to number theory, we present a comparative study of the accuracies on different problems. The paradigm should be useful for conjecture formulation, finding more efficient methods of computation, as well as probing into certain hierarchy of structures in mathematics.

Statistical mechanics of systems with negative temperature

Publication date: Available online 5 April 2021

Source: Physics Reports

Author(s): Marco Baldovin, Stefano Iubini, Roberto Livi, Angelo Vulpiani

Probing new physics for $(g-2)_\mu$ and gravitational waves. (arXiv:2104.03519v1 [hep-ph])

Authors: Ruiyu ZhouLigong BianJing Shu

We study the possibility of probing new physics accounting for $(g-2)_\mu$ anomaly and gravitational waves with pulsar timing array measurements. The model we consider is either a light gauge boson or neutral scalar interacting with muons. We show that the parameter spaces of dark $U(1)$ model with kinetic mixing explaining $(g-2)_\mu$ anomaly can realize a first-order phase transition, and the yield-produced gravitational wave may address the common red noise observed in the NANOGrav 12.5-yr dataset.

Canonical structure of minimal varying $\Lambda$ theories. (arXiv:2104.03753v1 [gr-qc])

Minimal varying $\Lambda$ theories are defined by an action built from the Einstein-Cartan-Holst first order action for gravity with the cosmological constant $\Lambda$ as an independent scalar field, and supplemented by the Euler and Pontryagin densities multiplied by $1/\Lambda$. We identify the canonical structure of these theories which turn out to represent an example of irregular systems. We find five degrees of freedom on generic backgrounds and for generic values of parameters, whereas if the parameters satisfy a certain condition (which includes the most commonly considered Euler case) only three degrees of freedom remain. On de Sitter-like backgrounds the canonical structure changes, and due to an emergent conformal symmetry one degree of freedom drops from the spectrum. We also analyze the self-dual case with an holomorphic action depending only on the self-dual part of the connection. In this case we find two (complex) degrees of freedom, and further discuss the Kodama state, the restriction to de Sitter background and the effect of reality conditions.

Local Lorentz invariance tests for photons and hadrons at the Gamma Factory. (arXiv:2104.03784v1 [hep-ex])

Authors: B. WojtsekhowskiDmitry Budker

High-precision tests of local Lorentz invariance, via monitoring of the sidereal time variation of the photon energies emitted by ultrarelativistic heavy-ion beams and of the beam momentum, are proposed. This paper includes descriptions of the physics ideas and the concept for the detector. The experiment results will allow high-precision tests of LLI via anisotropy of the maximum attainable speed of a photon and an ion. The projected accuracy for the asymmetries interpreted in the framework of the anisotropic relativistic mechanics corresponds to the limit on sidereal time variation of the one-way maximum attainable speed at the levels between $10^{-14}$ and $10^{-17}$.

Possible existence of time machines in a five-dimensional spacetime. (arXiv:2104.03790v1 [gr-qc])

Authors: Peter K.F. Kuhfittig

The idea of constructing a time machine is not new and even received a boost thanks to the realization that a traversable wormhole could be converted to a time machine. This also implied that it would be impossible to travel back in time beyond the creation of the time machine. This paper addresses these issues, as well as the concomitant causality violations, by starting with a physically acceptable model, a spacetime that is anti-de Sitter due to an extra time-like dimension, thereby allowing the existence of closed time-like curves. By assuming that the extra dimension is independent of the radial coordinate, the wormhole retains its basic geometric properties regardless of its location and can therefore serve as a shortcut for any closed time-like curve, which, in turn, can extend indefinitely into the past. The same independence of the radial coordinate suggests that the wormhole could connect a region in the present to a local region that (1) lies in the past and (2) does not contain any closed time-like curves. Previous studies have suggested that if such a region is sufficiently localized, it may be possible to avoid a causality violation.

$T\bar T$ deformation on multi-quantum mechanics and regenesis. (arXiv:2104.03852v1 [hep-th])

Authors: Sone HeZhuo-Yu Xian

We study the $T\bar T$ deformation on a multi-quantum mechanical systems. By introducing the dynamical coordinate transformation, we obtain the deformed theory as well as the solution. We further study the thermo-field-double state under the $T\bar T$ deformation on these systems, including conformal quantum mechanical system, the Sachdev-Ye-Kitaev model, and the model satisfying Eigenstate Thermalization Hypothesis. We find common regenesis phenomena where the signal injected into one local system can regenerate from the other local system. From the bulk picture, we study the deformation on Jackiw-Teitelboim gravity governed by Schwarzian action and find that the regenesis phenomena here are not related to the causal structure of semi-classical wormhole.

Nerve rays on the brain

Nature Physics, Published online: 09 April 2021; doi:10.1038/s41567-021-01228-w

Nerve rays on the brain

One outstanding path from A to B

Nature Physics, Published online: 09 April 2021; doi:10.1038/s41567-021-01222-2

What does it mean for an individual to be ‘important’ or for a connection to be ‘outstanding’? The answer depends on context, as Sarah Shugars and Samuel V. Scarpino explain.

Phenomenal Roles: A Dispositional Account of Bodily Pain

Gozzano, Simone (2021) Phenomenal Roles: A Dispositional Account of Bodily Pain. [Preprint]

Applying Perspectival Realism to Frequentist Statistics: The Case of Jerzy Neyman’s Methodology and Philosophy

Kubiak, Adam P. (2021) Applying Perspectival Realism to Frequentist Statistics: The Case of Jerzy Neyman’s Methodology and Philosophy. In: UNSPECIFIED.

Testing Quantum Mechanics with an Ultra-Cold Particle Trap

by Peter J. Riggs

It is possible to empirically discriminate between the predictions of orthodox (i.e., Copenhagen) quantum theory and the de Broglie−Bohm theory of quantum mechanics. A practical experiment is proposed in which a single, laser-cooled ion inside an ultra-cold particle trap is either found to be near the trap’s walls or not. Detections of the former kind would support the prediction of orthodox quantum theory and of the latter kind would support the de Broglie−Bohm theory. The outcome of this experiment would show which theory gives the more correct description and, consequently, would have far-reaching implications for our understanding of quantum mechanics. View Full-Text