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.

Gravitational Effects in Quantum Mechanics. (arXiv:1602.03878v1 [quant-ph])

on 2016-2-13 7:49am GMT

Authors: A. D. K. Plato, C. N. Hughes, M. S. Kim

To date, both quantum theory, and Einstein’s theory of general relativity have passed every experimental test in their respective regimes. Nevertheless, almost since their inception, there has been debate surrounding whether they should be unified and by now there exists strong theoretical arguments pointing to the necessity of quantising the gravitational field. In recent years, a number of experiments have been proposed which, if successful, should give insight into features at the Planck scale. Here we review some of the motivations, from the perspective of semi-classical arguments, to expect new physical effects at the overlap of quantum theory and general relativity. We conclude with a short introduction to some of the proposals being made to facilitate empirical verification.

on 2016-2-13 7:49am GMT

Authors: Lajos Diósi

Fundamental modifications of the standard Schr\”odinger equation by additional nonlinear terms have been considered for various purposes over the recent decades. It came as a surprise when, inverting Abner Shimony’s observation of “peaceful coexistence” between standard quantum mechanics and relativity, N. Gisin proved in 1990 that any (deterministic) nonlinear Schr\”odinger equation would allow for superluminal communication. This is by now the most spectacular and best known anomaly. We discuss further anomalies, simple but foundational, less spectacular but not less dramatic.

Resolving the problem of definite outcomes of measurements. (arXiv:1602.03863v1 [quant-ph])

on 2016-2-13 7:49am GMT

Authors: Art Hobson

The entangled “Schrodinger’s cat” state of a quantum and its measurement apparatus is not a superposition of quantum states but is instead a non-paradoxical superposition of nonlocal correlations between quantum states. This elucidation of entanglement is demonstrated by experiments conducted in 1990 using entangled photon pairs. Thus the Schrodinger’s cat state does not predict a dead-and-alive cat. Instead of indefinite superpositions, it predicts indeterminate but definite outcomes. When a superposed quantum entangles with a measurement apparatus, the composite system instantly collapses locally to incoherent mixtures of definite outcomes of the quantum and of the apparatus, while the global superposition of correlations maintains its unitary evolution. This transfer of coherence from the quantum system to correlations between the system and its measuring apparatus is the reason instantaneous local collapse can occur upon measurement without interrupting the smooth global evolution that follows Schrodinger’s equation. Objections to this resolution (namely improper density operators, and basis ambiguity) are rebutted.

on 2016-2-13 7:49am GMT

Authors: Justyna Łodyga, Waldemar Kłobus, Andrzej Grudka, Michał Horodecki, Ryszard Horodecki

Heisenberg uncertainty principle is a trademark of quantum mechanics. In its original form it states that one cannot gain information about a system without disturbing it, which is a core of novel cryptographic techniques based on quantum effects. The principle can be derived from mathematical formalism of quantum theory. However the formalism itself is very abstract – unlike in classical mechanics, it does not directly refer to what we perceive. The question arises: can we derive the principle from more comprehensible assumptions? Here we derive Heisenberg trade-off from two assumptions: impossibility of instantaneous messaging at a distance (no-signaling), and violation of Bell inequalities (non-locality). The former is a natural and simple assumption, while the latter is an observable phenomenon implied by quantum mechanics. That the trade-off is a consequence of the above two assumptions is indirectly implied by existing schemes of secure cryptography based on the above two assumptions. Surprisingly, despite of vast literature on such crypto-systems, no direct connection between no-signaling, non-locality and Heisenberg principle was ever proposed. We also analyze a Bayesian trade-off, and note that there exists a range of parameters, where assumptions of no-signaling precisely reconstruct quantum predictions.

on 2016-2-13 7:48am GMT

Authors: Steven B. Giddings

A preliminary discussion is given of the prospects that gravitational-wave observations of binary inspiral of black holes could reveal or constrain quantum modifications to black hole dynamics, such as are required to preserve postulates of quantum mechanics. Different proposals for such modifications are characterized by different scales, and the size of these scales relative to those probed by observation of inspiral signals is important in determining the feasibility of finding experimental signatures. Certain scenarios with strong quantum modifications in a region extending well outside the horizon are expected to modify classical evolution, and distort the near-peak gravitational wave signal, suggesting a search for anomalies such as decreased regularity of the signal and increased power.

Induced Gravity and Topological Quantum Field Theory. (arXiv:1602.03478v1 [gr-qc])

on 2016-2-11 1:34am GMT

Authors: Ichiro Oda

We construct an induced gravity (pregeometry) where both the Newton constant and the cosmological constant appear as integration constants in solving field equations. By adding the kinetic terms of ghosts and antighosts, an action of the induced gravity is transformed to a topological field theory. Moreover, by solving field equations of the topological field theory in the FRW universe, we find an inflation solution. The present study might shed some light on a close relationship between the induced gravity and the topological quantum field theory.

Comments on New Ontology of Quantum Mechanics called CSM. (arXiv:1602.03495v1 [quant-ph])

on 2016-2-11 1:34am GMT

Authors: Marian Kupczynski

A new quantum ontology of quantum mechanics has been proposed recently. This ontology is based on impossible to realize measurements which need to be performed repeatedly on the same single physical system or on the same pair of physical systems. We agree that quantum mechanics is a contextual theory and that the experimental contexts have to be a part of any description of quantum phenomena but in our opinion this new ontology is neither convincing nor useful. In particular the authors claim that their ontology explains the peaceful coexistence between quantum mechanics and relativity in spin polarization correlation experiments. We show that, contrary to their claim, the authors are unable to explain why strong correlations, between the outcomes of distant local measurements, do exist and why they preserve a condition of parameter independence (non-signaling). Strangely enough the authors ignore that these strong but imperfect correlations can be explained in a local and causal way using statistical contextual interpretation of quantum mechanics what was demonstrated in several articles.

On the Conceptual Issues Surrounding the Notion of Relational Bohmian Dynamics

Latest Results for Foundations of Physics

on 2016-2-11 12:00am GMT

**Abstract**

The paper presents a program to construct a non-relativistic relational Bohmian theory, that is, a theory of *N* moving point-like particles that dispenses with space and time as fundamental background structures. The relational program proposed is based on the best-matching framework originally developed by Julian Barbour. In particular, the paper focuses on the conceptual problems that arise when trying to implement such a program. It is argued that pursuing a relational strategy in the Bohmian context leads to a more parsimonious ontology than that of standard Bohmian mechanics without betraying the original motivations for adopting a primitive ontology approach to quantum physics. It is also shown how a relational Bohmian approach might clarify the issue of the timelessness of the dynamics resulting from the quantization of a classical relational system of particles.

Does Bohm’s Quantum Force Have a Classical Origin?

Latest Results for Foundations of Physics

on 2016-2-08 12:00am GMT

**Abstract**

In the de Broglie–Bohm formulation of quantum mechanics, the electron is stationary in the ground state of hydrogenic atoms, because the quantum force exactly cancels the Coulomb attraction of the electron to the nucleus. In this paper it is shown that classical electrodynamics similarly predicts the Coulomb force can be effectively canceled by part of the magnetic force that occurs between two similar particles each consisting of a point charge moving with circulatory motion at the speed of light. Supposition of such motion is the basis of the *Zitterbewegung* interpretation of quantum mechanics. The magnetic force between two luminally-circulating charges for separation large compared to their circulatory motions contains a radial inverse square law part with magnitude equal to the Coulomb force, sinusoidally modulated by the phase difference between the circulatory motions. When the particles have equal mass and their circulatory motions are aligned but out of phase, part of the magnetic force is equal but opposite the Coulomb force. This raises a possibility that the quantum force of Bohmian mechanics may be attributable to the magnetic force of classical electrodynamics. It is further shown that relative motion between the particles leads to modulation of the magnetic force with spatial period equal to the de Broglie wavelength.