# Weekly Papers on Quantum Foundations (45)

This is a list of this week’s papers on quantum foundations published in various journals or uploaded to preprint servers such as arxiv.org and PhilSci Archive.

The measurement problem is the measurement problem is the measurement problem. (arXiv:1611.01111v1 [quant-ph])

on 2016-11-05 8:00am GMT

Authors: Veronika BaumannArne HansenStefan Wolf

Recently, it has been stated that single-world interpretations of quantum theory are logically inconsistent. The claim is derived from contradicting statements of agents in a setup combining two Wigner’s-friend experiments. Those statements stem from applying the measurement-update rule subjectively, i.e., only for the respective agent’s own measurement. We argue that the contradiction expresses the incompatibility of collapse and unitarity – resulting in different formal descriptions of a measurement – and does not allow to dismiss any specific interpretation of quantum theory.

Gravity can significantly modify classical and quantum Poincare recurrence theorems. (arXiv:1611.00792v1 [gr-qc])

on 2016-11-05 8:00am GMT

Authors: Ruifeng DongDejan Stojkovic

Poincare recurrence theorem states that any finite system will come arbitrary close to its initial state after some very long but finite time. At the statistical level, this by itself does not represent a paradox, but apparently violates the second law of thermodynamics, which may lead to some confusing conclusions for macroscopic systems. However, this statement does not take gravity into account. If two particles with a given center of mass energy come at the distance shorter than the Schwarzschild diameter apart, according to classical gravity they will form a black hole. In the classical case, a black hole once formed will always grow and effectively quench the Poincare recurrence. We derive the condition under which the classical black hole production rate is higher than the classical Poincare recurrence rate. In the quantum case, if the temperature of the black hole is lower than the temperature of the surrounding gas, such a black hole cannot disappear via Hawking evaporation. We derive the condition which gives us a critical temperature above which the black hole production is faster than quantum Poincare recurrence time. However, in quantum case, the quantum Poincare recurrence theorem can be applied to the black hole states too. The presence of the black hole can make the recurrence time longer or shorter, depending on whether the presence of the black hole increases or decreases the total entropy. We derive the temperature below which the produced black hole increases the entropy of the whole system (gas particles plus a black hole). Finally, if evolution of the system is fast enough, then newly formed black holes will merge and accrete particles until one large black hole dominates the system. We give the temperature above which the presence of black holes increase the entropy of the whole system and prolongs the Poincare recurrence time.

Lagrangian Description for Particle Interpretations of Quantum Mechanics: Entangled Many-Particle Case

Latest Results for Foundations of Physics

on 2016-11-05 12:00am GMT

Abstract

A Lagrangian formulation is constructed for particle interpretations of quantum mechanics, a well-known example of such an interpretation being the Bohm model. The advantages of such a description are that the equations for particle motion, field evolution and conservation laws can all be deduced from a single Lagrangian density expression. The formalism presented is Lorentz invariant. This paper follows on from a previous one which was limited to the single-particle case. The present paper treats the more general case of many particles in an entangled state. It is found that describing more than one particle while maintaining a relativistic description requires the specification of final boundary conditions as well as the usual initial ones, with the experimenter’s controllable choice of the final conditions thereby exerting a backwards-in-time influence. This retrocausality then allows an important theoretical step forward to be made, namely that it becomes possible to dispense with the usual, many-dimensional description in configuration space and instead revert to a description in space–time using separate, single-particle wavefunctions.

Algorithmic Construction of Local Hidden Variable Models for Entangled Quantum States

PRL: General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

on 2016-11-04 2:00pm GMT

Author(s): Flavien Hirsch, Marco Túlio Quintino, Tamás Vértesi, Matthew F. Pusey, and Nicolas Brunner

Constructing local hidden variable (LHV) models for entangled quantum states is a fundamental problem, with implications for the foundations of quantum theory and for quantum information processing. It is, however, a challenging problem, as the model should reproduce quantum predictions for all poss…

[Phys. Rev. Lett. 117, 190402] Published Fri Nov 04, 2016

General Method for Constructing Local Hidden Variable Models for Entangled Quantum States

PRL: General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

on 2016-11-04 2:00pm GMT

Author(s): D. Cavalcanti, L. Guerini, R. Rabelo, and P. Skrzypczyk

Entanglement allows for the nonlocality of quantum theory, which is the resource behind device-independent quantum information protocols. However, not all entangled quantum states display nonlocality. A central question is to determine the precise relation between entanglement and nonlocality. Here …

[Phys. Rev. Lett. 117, 190401] Published Fri Nov 04, 2016

Emergence and mechanism in the fractional quantum Hall effect

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

on 2016-11-04 12:08pm GMT

Publication date: Available online 2 November 2016
Source:Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics
Author(s): Jonathan Bain
For some authors, an adequate notion of emergence must include an account of a mechanism by means of which emergent behavior is realized. This appeal to mechanism is problematic in the case of the fractional quantum Hall effect (FQHE). There is a consensus among physicists that the FQHE exhibits emergent phenomena, but there are at least four alternative explanations of the latter that, arguably, appeal to ontologically distinct mechanisms, both at the microphysics level and at the level of general organizing principles. In light of this underdetermination of mechanism, one is faced with the following options: (I) deny that emergence is present in the FQHE; (II) argue for the priority of one mechanistic explanation over the others; or (III) temper the desire for a mechanism-centric account of emergence. I will argue that there are good reasons to reject (I) and (II) and accept (III). In particular, I will suggest that a law-centric account of emergence does just fine in explaining the emergent phenomena associated with the FQHE.

Ψ-epistemic quantum cosmology?

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

on 2016-11-04 12:08pm GMT

Publication date: Available online 4 November 2016
Source:Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics
Author(s): Peter W. Evans, Sean Gryb, Karim P.Y. Thébault
This paper provides a prospectus for a new way of thinking about the wavefunction of the universe: a Ψ-epistemic quantum cosmology. We present a proposal that, if successfully implemented, would resolve the cosmological measurement problem and simultaneously allow us to think sensibly about probability and evolution in quantum cosmology. Our analysis draws upon recent work on the problem of time in quantum gravity and causally symmetric local hidden variable theories. Our conclusion weighs the strengths and weaknesses of the approach and points towards paths for future development.

What is quantum information?

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

on 2016-11-04 12:08pm GMT

Publication date: Available online 3 November 2016
Source:Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics
Author(s): Olimpia Lombardi, Federico Holik, Leonardo Vanni
In the present article we address the question ‘What is quantum information?’ from a conceptual viewpoint. In particular, we argue that there seems to be no sufficiently good reasons to accept that quantum information is qualitatively different from classical information. The view that, in the communicational context, there is only one kind of information, physically neutral, which can be encoded by means of classical or quantum states has, in turn, interesting conceptual advantages. First, it dissolves the widely discussed puzzles of teleportation without the need to assume a particular interpretation of information. Second, and from a more general viewpoint, it frees the attempts to reconstruct quantum mechanics on the basis of informational constraints from any risk of circularity; furthermore, it endows them with a strong conceptual appealing and, derivatively, opens the way to the possibility of a non-reductive unification of physics. Finally, in the light of the idea of the physical neutrality of information, the wide field of research about classical models for quantum information acquires a particular conceptual and philosophical interest.

[Perspective] A testing time for antimatter

Science: Current Issue

on 2016-11-04 12:00am GMT

Spectroscopy is the most accurate branch of science. Optical transition frequencies in isolated atoms and molecules can nowadays be measured to many-digit accuracies by applying the tools developed in the atomic physics community: ultrastable lasers, locked via frequency-comb lasers to atomic clocks, and the techniques to cool and control the motion of atoms. Precision measurements on small quantum systems can be compared with theoretical descriptions of these systems at the most fundamental level, allowing physics theories to be tested and enabling the search for physics beyond the standard model (1). On page 610 of this issue, Hori et al. (2) apply these tricks of the trade to a small atomic quantum system with a built-in antiparticle to perform precise spectroscopic measurement in antiprotonic helium (see the figure). The technique of buffer-gas cooling is demonstrated for the first time on a composite matter–antimatter particle. Author: Wim Ubachs

[Report] Universal space-time scaling symmetry in the dynamics of bosons across a quantum phase transition

Science: Current Issue

on 2016-11-04 12:00am GMT

The dynamics of many-body systems spanning condensed matter, cosmology, and beyond are hypothesized to be universal when the systems cross continuous phase transitions. The universal dynamics are expected to satisfy a scaling symmetry of space and time with the crossing rate, inspired by the Kibble-Zurek mechanism. We test this symmetry based on Bose condensates in a shaken optical lattice. Shaking the lattice drives condensates across an effectively ferromagnetic quantum phase transition. After crossing the critical point, the condensates manifest delayed growth of spin fluctuations and develop antiferromagnetic spatial correlations resulting from the sub-Poisson distribution of the spacing between topological defects. The fluctuations and correlations are invariant in scaled space-time coordinates, in support of the scaling symmetry of quantum critical dynamics. Authors: Logan W. Clark, Lei Feng, Cheng Chin

Timescale for adiabaticity breakdown in driven many-body systems and orthogonality catastrophe. (arXiv:1611.00663v1 [cond-mat.quant-gas])

on 2016-11-03 7:31am GMT

The adiabatic theorem is a fundamental result established in the early days of quantum mechanics, which states that a system can be kept arbitrarily close to the instantaneous ground state of its Hamiltonian if the latter varies in time slowly enough. The theorem has an impressive record of applications ranging from foundations of quantum field theory to computational recipes in molecular dynamics. In light of this success it is remarkable that a practicable quantitative understanding of what “slowly enough” means is limited to a modest set of systems mostly having a small Hilbert space. Here we show how this gap can be bridged for a broad natural class of physical systems, namely many-body systems where a small move in the parameter space induces an orthogonality catastrophe. In this class, the conditions for adiabaticity are derived from the scaling properties of the parameter dependent ground state without a reference to the excitation spectrum. This finding constitutes a major simplification of a complex problem, which otherwise requires solving non-autonomous time evolution in a large Hilbert space. We illustrate our general results on two examples motivated by recent experiments on Thouless pumping and on the dynamics of an impurity in a degenerate quantum fluid.

Separability in gauge theories

Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2016-11-02 6:41pm GMT

Dougherty, John (2016) Separability in gauge theories. In: UNSPECIFIED.

The Most General Form of Deformation of the Heisenberg Algebra from the Generalized Uncertainty Principle. (arXiv:1611.00001v1 [hep-th])

on 2016-11-02 7:53am GMT

In this paper, we will propose the most general form of the deformation of Heisenberg algebra motivated by the generalized uncertainty principle. This deformation of the Heisenberg algebra will deform all quantum mechanical systems. The form of the generalized uncertainty principle used to motivate these results will be motivated by space fractional quantum mechanics and non-locality in quantum mechanical systems. We also analyse a specific limit of this generalized deformation for one dimensional system, and in that limit, a nonlocal deformation of the momentum operator generates a local deformation of all one dimensional quantum mechanical systems. We analyse the low energy effects of this deformation on a harmonic oscillator, Landau levels, Lamb shift, and potential barrier. We also demonstrate that this deformation leads to a discretization of space.

Weak Measurement and Two-State-Vector Formalism: Deficit of Momentum Transfer in Scattering Processes. (arXiv:1611.00272v1 [quant-ph])

on 2016-11-02 7:53am GMT

Authors: C. A. Chatzidimitriou-Dreismann

The notions of weak measurement, weak value, and two-state-vector formalism provide a new quantum-theoretical frame for extracting additional information from a system in the limit of small disturbances to its state. Here, we provide an application to the case of two-body scattering with one body weakly interacting with an environment. The direct connection to real scattering experiments is pointed out by making contact with the field of impulsive incoherent neutron scattering from molecules and condensed systems. In particular, we predict a new quantum effect in neutron-atom collisions, namely an observable momentum transfer deficit; or equivalently, a reduction of effective mass below that of the free scattering atom. Two corroborative experimental findings are shortly presented. Implications for current and further experiments are mentioned. An interpretation of this effect and the associated experimental results within conventional theory is currently unavailable.

Scientific Realism and Primitive Ontology

Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2016-11-02 4:11am GMT

Allori, Valia (2016) Scientific Realism and Primitive Ontology. In: UNSPECIFIED.

Fluid dynamics: Turbulence in a quantum gas

Nature Physical Sciences Research

on 2016-11-02 12:00am GMT

The discovery of a cascade of sound waves across many wavelengths in an ultracold atomic gas advances our understanding of turbulence in fluids governed by quantum mechanics. See Letter p.72

Nature 539 36 doi: 10.1038/539036a

On the notion of free will in the Free Will Theorem

Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2016-11-01 5:07pm GMT

Landsman, Klaas (2016) On the notion of free will in the Free Will Theorem. [Preprint]

A local and operational framework for the foundations of physics. (arXiv:1610.09052v1 [quant-ph])

on 2016-10-31 5:22am GMT

Authors: Robert Oeckl (CCM-UNAM)

We discuss a novel framework for physical theories that is based on the principles of locality and operationalism. It generalizes and unifies previous frameworks, including the standard formulation of quantum theory, the convex operational framework and Segal’s approach to quantum field theory. It is capable of encoding both classical and quantum (field) theories, implements spacetime locality in a manifest way and contains the complete modern notion of measurement in the quantum case. Its mathematical content can be condensed into a set of axioms that are similar to those of Atiyah and Segal. This is supplemented by two basic rules for extracting probabilities or expectation values for measurement processes. The framework, called the positive formalism, is derived in three completely different ways. One derivation is from first principles, one starts with classical field theory and one with quantum field theory. The latter derivation arose previously in the programme of the general boundary formulation of quantum theory. As in the convex operational framework, the difference between classical and quantum theories essentially arises from certain partially ordered vector spaces being either lattices or anti-lattices. If we add the ad hoc ingredient of imposing anti-lattice structures, the derivation from first principles may be seen as a reconstruction of quantum theory. Among other things, the positive formalism suggests a statistical approach to classical field theories with dynamical metric, provides a common ground for quantum information theory and quantum field theory, introduces a notion of local measurement into quantum field theory, and suggests a new perspective on quantum gravity by removing the incompatibility with general relativistic principles.

The Case of the Disappearing (and Re-Appearing) Particle. (arXiv:1610.09025v1 [quant-ph])

on 2016-10-31 5:22am GMT

A novel prediction is derived by the Two-State-Vector-Formalism (TSVF) for a particle superposed over three boxes. Under appropriate pre- and postselections, and with tunneling enabled between two of the boxes, it is possible to derive not only one, but three predictions for three different times within the intermediate interval. These predictions are moreover contradictory: The particle (when looked for using a projective measurement) seems to disappear from the first box where it would have been previously found with certainty, appearing instead within the third box, to which no tunneling is possible, and later re-appearing within the second. When examined closer during the “disappearance” time, it turns out that local measurement (i.e. opening one of the boxes) fails to indicate the particle’s presence, but subtler measurements performed on the two boxes together reveal the particle’s nonlocal modular momentum spatially separated from its mass. Another advance of this setting is that, unlike other predictions of the TSVF that rely on weak and/or counterfactual measurements, the present one uses actual projective measurements. This outcome is then corroborated by adding weak measurements and the Aharonov-Bohm effect. The results strengthen the recently suggested time-symmetric Heisenberg ontology based on nonlocal deterministic operators.

Spontaneous collapse: a solution to the measurement problem and a source of the decay in mesonic systems. (arXiv:1606.01682v2 [quant-ph] UPDATED)

on 2016-10-31 5:22am GMT

Authors: K. SimonovB.C. Hiesmayr

Dynamical reduction models propose a solution to the measurement problem in quantum mechanics: the collapse of the wave function becomes a physical process. We compute the predictions to decaying and Dynamical reduction models propose a solution to the measurement problem in quantum mechanics: the collapse of the wave function becomes a physical process. We compute the predictions to decaying and flavor–oscillating neutral mesons for the two most promising collapse models, the QMUPL (Quantum Mechanics with Universal Position Localization) model and the mass-proportional CSL (Continuous Spontaneous Localization) model. Our results are showing (i) a strong sensitivity to the very assumptions of the noise field underlying those two collapse models and (ii) under particular assumptions the CSL case allows even to recover the decay dynamics. This in turn allows to predict the effective collapse rates solely based on the measured values for the oscillation (mass differences) and the measured values of the decay constants. The four types of neutral mesons ($K$-meson, $D$-meson, $B_d$-meson, $B_s$-meson) lead surprisingly to ranges comparable to those put forward by Adler (2007) and Ghirardi-Rimini-Weber (1986). Our results show that these systems at high energies are very sensitive to possible modifications of the standard quantum theory making them a very powerful laboratory to rule out certain collapse scenarios and studying the detailed physical processes solving the measurement problem.

Measuring the deviation from the superposition principle in interference experiments. (arXiv:1610.09143v1 [quant-ph])

on 2016-10-31 5:22am GMT

The superposition principle forms the heart of all modern applications and properties of Quantum Mechanics including Quantum Computing and Quantum Entanglement. However, its usual application to slit based interference experiments has caveat in both Optics and Quantum Mechanics where it is often incorrectly assumed that the boundary condition represented by slits opened individually is same as them being opened together. Error entailed by this assumption is quantified by a parameter which has been calculated by recent theoretical works to be non-zero under correct boundary conditions. No experiment till date has reported a non-zero value for this quantity $\kappa$ yet. Here we report the first measurement of a non-zero $\kappa$ of the order $10^{-2}$ in the microwave domain using antennas as sources and detectors of the electromagnetic waves. With remarkable agreement between experiment and theory, we convincingly demonstrate the deviation from the usual application of the superposition principle. We also show that our results can have potential applications in formulating better error models in observational radio astronomy data in studies of the epoch of reionization of the early universe where similar naive assumptions are sometimes made about the application of the superposition principle.

Quantum optics: Photons taught new tricks

Nature Physics – AOP – nature.com science feeds

on 2016-10-31 12:00am GMT

Nature Physics. doi:10.1038/nphys3948

Experiments of the Aharonov–Bohm type typically involve particles that are charged and interact with a magnetic flux. Photons aren’t the former and don’t do the latter. Yet, an Aharonov–Bohm ring for photons has just been realized experimentally.

Classical limit and quantum logic

Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2016-10-29 8:45pm GMT

Fortin, Sebastian and Holik, Federico (2016) Classical limit and quantum logic. In: UNSPECIFIED.

Anthropic arguments outside of cosmology and string theory

Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2016-10-29 8:45pm GMT

Cirkovic, Milan (2016) Anthropic arguments outside of cosmology and string theory. [Preprint]