Weekly Papers on Quantum Foundations (22)

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

Multiple choices of time in quantum cosmology

Classical and Quantum Gravity – latest papers

on 2015-5-28 12:00am GMT

It is often conjectured that a choice of time function merely sets up a frame for the quantum evolution of the gravitational field, meaning that all choices should be in some sense compatible. In order to explore this conjecture (and the meaning of compatibility), we develop suitable tools for determining the relation between quantum theories based on different time functions. First, we discuss how a time function fixes a canonical structure on the constraint surface. The presentation includes both the kinematical and the reduced perspective, and the relation between them. Second, we formulate twin theorems about the existence of two inequivalent maps between any two deparameterizations, a formal canonical and a coordinate one. They are used to separate the effects induced by choice of clock and other factors. We show, in an example, how the spectra of quantum observables are transformed under the change of clock and prove, via a general argument, the existence of c…

Frozen Quantum Coherence

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

on 2015-5-27 2:00pm GMT

Author(s): Thomas R. Bromley, Marco Cianciaruso, and Gerardo Adesso

We analyze under which dynamical conditions the coherence of an open quantum system is totally unaffected by noise. For a single qubit, specific measures of coherence are found to freeze under different conditions, with no general agreement between them. Conversely, for an N-qubit system with even N…

[Phys. Rev. Lett. 114, 210401] Published Wed May 27, 2015

Equivalent emergence of time dependence in classical and quantum mechanics

PRA: Fundamental concepts

on 2015-5-26 2:00pm GMT

Author(s): John S. Briggs

Beginning with the principle that a closed mechanical composite system is timeless, time can be defined by the regular changes in a suitable position coordinate (clock) in the observing part, when one part of the closed composite observes another part. Translating this scenario into both classical a…

[Phys. Rev. A 91, 052119] Published Tue May 26, 2015

Demonstrating genuine multipartite entanglement and nonseparability without shared reference frames

PRA: Fundamental concepts

on 2015-5-26 2:00pm GMT

Author(s): Celal Furkan Senel, Thomas Lawson, Marc Kaplan, Damian Markham, and Eleni Diamanti

Multipartite nonlocality is of great fundamental interest and constitutes a useful resource for many quantum information protocols. However, demonstrating it in practice, by violating a Bell inequality, can be difficult. In particular, standard experimental setups require the alignment of distant pa…

[Phys. Rev. A 91, 052118] Published Tue May 26, 2015

Schr\”odinger Equation of a particle in an Uniformly Accelerated Frame and the Possibility of a New kind of Quanta. (arXiv:1505.05495v1 [gr-qc] CROSS LISTED)

quant-ph updates on arXiv.org

on 2015-5-25 12:56pm GMT

Authors: Sanchari DeSomenath Chakrabarty

In this article we have developed a formalism to obtain the Schr$\ddot{\rm{o}}$dinger equation for a particle in a frame undergoing an uniform acceleration in an otherwise flat Minkowski space-time geometry. We have presented an exact solution of the equation and obtained the eigenfunctions and the corresponding eigenvalues. It has been observed that the Schr$\ddot{\rm{o}}$dinger equation can be reduced to an one dimensional hydrogen atom problem. Whereas, the quantized energy levels are exactly identical with that of an one dimensional quantum harmonic oscillator. Hence considering transitions, we have predicted the existence of a new kind of quanta, which will either be emitted or absorbed if the particles get excited or de-excited respectively.

Wheeler’s delayed-choice gedanken experiment with a single atom

Nature Physics – AOP – nature.com science feeds

on 2015-5-25 12:00am GMT

Nature Physics. doi:10.1038/nphys3343

Authors: A. G. Manning, R. I. Khakimov, R. G. Dall & A. G. Truscott

The wave–particle dual nature of light and matter and the fact that the choice of measurement determines which one of these two seemingly incompatible behaviours we observe are examples of the counterintuitive features of quantum mechanics. They are illustrated by Wheeler’s famous ‘delayed-choice’ experiment, recently demonstrated in a single-photon experiment. Here, we use a single ultracold metastable helium atom in a Mach–Zehnder interferometer to create an atomic analogue of Wheeler’s original proposal. Our experiment confirms Bohr’s view that it does not make sense to ascribe the wave or particle behaviour to a massive particle before the measurement takes place. This result is encouraging for current work towards entanglement and Bell’s theorem tests in macroscopic systems of massive particles.


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