|上午9:44|||||Emmanuel Zambrini Cruzeiro, Nicolas Gisin, Sandu Popescu|||||quant-ph updates on arXiv.org|
Steering is usually described as a quantum phenomenon. In this article, we show that steering is not restricted to quantum theory, it is also present in more general, no-signalling theories. We present two main results: first, we show that quantum steering involves a collection of different aspects, which need to be separated when considering steering in no-signalling theories. By deconstructing quantum steering, we learn more about the nature of the steering phenomenon itself. Second, we introduce a new concept, that we call “blind steering”, which can be seen as the most basic form of steering, present both in quantum mechanics and no-signalling theories.
|上午9:44|||||physics.hist-ph updates on arXiv.org|
Authors: A. S. Sanz
The ontological aspect of Bohmian mechanics, as a hidden-variable theory that provides us with an objective description of a quantum world without observers, is widely known. Yet its practicality is getting more and more acceptance and relevance, for it has proven to be an efficient and useful resource to tackle, explore, describe and explain such phenomena. This practical aspect emerges precisely when the pragmatic application of the formalism prevails over any other interpretational question, still a matter of debate and controversy. In this regard, the purpose here is to show and discuss how Bohmian mechanics emphasizes in a natural manner a series of dynamical features difficult to find out through other quantum approaches. This arises from the fact that Bohmian mechanics allows us to establish a direct link between the dynamics exhibited by quantum systems and the local variations of the quantum phase associated with their state. To illustrate these facts, simple models of two physically insightful quantum phenomena have been chosen, namely, the dispersion of a free Gaussian wave packet and Young-type two-slit interference. As it is shown, the outcomes from their analysis render a novel, alternative understanding of the dynamics displayed by these quantum phenomena in terms of the underlying local velocity field that connects the probability density with the quantum flux. This field, nothing but the so-called guidance condition in standard Bohmian mechanics, thus acquires a prominent role to understand quantum dynamics, as the mechanism responsible for such dynamics. This goes beyond the passive role typically assigned to this field in Bohmian mechanics, where traditionally trajectories and quantum potentials have received more attention instead.
|上午9:44|||||physics.hist-ph updates on arXiv.org|
Authors: Aurélien Drezet
We address the question of whether a non-nomological (i.e., anomic) interpretation of the wavefunction is compatible with the quantum formalism. After clarifying the distinction between ontic, epistemic, nomic and anomic models we focus our attention on two famous no-go theorems due to Pusey, Barrett, and Rudolph (PBR) on the one side and Hardy on the other side which forbid the existence of anomic-epistemic models. Moreover, we demonstrate that the so called restricted ontic indifference introduced by Hardy induces new constraints. We show that after modifications the Hardy theorem actually rules out all anomic models of the wavefunction assuming only restricted ontic indifference and preparation independence.
|上午9:44|||||gr-qc updates on arXiv.org|
The problem of time is one of the most relevant open issues in canonical quantum gravity. Although there is a huge literature about this topic, a commonly accepted solution has not been found yet. Here, we focus on the semiclassical approach to the problem of time, that has the main goal of reproducing quantum field theory on a fixed WKB background accounting also for quantum gravity corrections. We analyze the different choices of the expansion parameter and discuss the problems arising in previous proposals, where a non-unitary evolution emerges as an effect of quantum gravity corrections. In this work we develop a new approach to solve this problem by performing the WKB expansion with the introduction of the so-called kinematical action as a clock for quantum matter, that allows to recover a unitary dynamics.
|2021年5月14日 星期五 上午8:00|||||Dmitry I. Pikulin|||||Nature Physics – Issue – nature.com science feeds|
Nature Physics, Published online: 14 May 2021; doi:10.1038/s41567-021-01261-9
Addendum: Topological superconductivity: Quantized, finally
|2021年5月12日 星期三 上午8:00|||||Latest Results for Synthese|
Hans Reichenbach’s position in the debate over scientific realism is remarkable. On the one hand, he endorsed the programmatic premises of logical empiricism; on the other, he explicitly employed a realist approach to conceptions such as reference, causality, and inference to the best explanation. How could that work out? It will be shown in the present paper that in Reichenbach’s view scientific realism is not, as frequently assumed, opposed to logical empiricism but rather to logical positivism. A distinction without a difference? Not at all, at least for Reichenbach. As is well known, his particular—probabilistic—variant of logical empiricism was intended to circumvent what he considered the shortcomings of the Vienna Circle’s verificationist (reductionist) approach to the language of science. In Experience and Prediction (1938), Reichenbach became most explicit in this regard. However, I shall argue that his position remained notoriously unstable in the end. It oscillated between a full-fledged scientific realist reading and an eminently pragmatist reading. Nevertheless, Reichenbach’s contribution proved instrumental in preparing subsequent efforts at reconciling logical empiricism and scientific realism.
|2021年5月11日 星期二 上午8:00|||||Richard Brierley|||||Nature Physics – Issue – nature.com science feeds|
Nature Physics, Published online: 11 May 2021; doi:10.1038/s41567-021-01250-y
Detect, don’t destroy
|2021年5月11日 星期二 上午8:00|||||Jessica Esquivel|||||Nature Physics – Issue – nature.com science feeds|
Nature Physics, Published online: 11 May 2021; doi:10.1038/s41567-021-01241-z
A love letter to Black feminist physicists
|2021年5月11日 星期四 上午9:00|||||Philsci-Archive: No conditions. Results ordered -Date Deposited.|
Gao, Shan (2021) A no-go result for QBism. [Preprint]