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.

A brief history of the multiverse. (arXiv:1512.01203v1 [hep-th])

on 2015-12-05 4:07am GMT

Authors: Andrei Linde

The theory of the inflationary multiverse changes the way we think about our place in the world. According to its most popular version, our world may consist of infinitely many exponentially large parts, exhibiting different sets of low-energy laws of physics. Since these parts are extremely large, the interior of each of them behaves as if it were a separate universe, practically unaffected by the rest of the world. This picture, combined with the theory of eternal inflation and anthropic considerations, may help to solve many difficult problems of modern physics, including the cosmological constant problem. In this article I will briefly describe this theory and provide links to the some hard to find papers written during the first few years of the development of the inflationary multiverse scenario.

How device-independent approaches change the meaning of Physics. (arXiv:1512.01035v1 [quant-ph])

on 2015-12-05 4:06am GMT

Authors: Alexei Grinbaum

Dirac sought an interpretation of mathematical formalism in terms of physical entities and Einstein insisted that physics should describe “the real states of the real systems”. While Bell inequalities put into question the reality of states, modern device-independent approaches do away with the idea of entities: physics is not built of physical systems. Focusing on the correlations between operationally defined inputs and outputs, device-independent methods promote a view more distant from conventional theory than Einstein’s ‘principle theories’ were from ‘constructive theories’. On the examples of indefinite causal orders and almost quantum correlations, we ask a puzzling question: if physical theory is not about systems, then what is it about? The answer given by the device-independent models is that physics is about languages. In moving away from the information-theoretic reconstructions of quantum theory, this answer marks a new conceptual development in the foundations of physics.

The GTR-model: a universal framework for quantum-like measurements. (arXiv:1512.00880v1 [quant-ph])

on 2015-12-05 4:06am GMT

Authors: Diederik Aerts, Massimiliano Sassoli de Bianchi

We present a very general geometrico-dynamical description of physical or more abstract entities, called the ‘general tension-reduction’ (GTR) model, where not only states, but also measurement-interactions can be represented, and the associated outcome probabilities calculated. Underlying the model is the hypothesis that indeterminism manifests as a consequence of unavoidable fluctuations in the experimental context, in accordance with the ‘hidden-measurements interpretation’ of quantum mechanics. When the structure of the state space is Hilbertian, and measurements are of the ‘universal’ kind, i.e., are the result of an average over all possible ways of selecting an outcome, the GTR-model provides the same predictions of the Born rule, and therefore provides a natural completed version of quantum mechanics. However, when the structure of the state space is non-Hilbertian and/or not all possible ways of selecting an outcome are available to be actualized, the predictions of the model generally differ from the quantum ones, especially when sequential measurements are considered. Some paradigmatic examples will be discussed, taken from physics and human cognition. Particular attention will be given to some known psychological effects, like question order effects and response replicability, which we show are able to generate non-Hilbertian statistics. We also suggest a realistic interpretation of the GTR-model, when applied to human cognition and decision, which we think could become the generally adopted interpretative framework in quantum cognition research.

[Perspective] Classical entanglement?

on 2015-12-04 12:00am GMT

Since the inception of quantum theory, scientists and philosophers have been puzzled by the apparent indeterminacy of physical properties prior to the measurement process. These problems suggest that quantum mechanics might ultimately be incompatible with basic notions of “realism”—that is, the view that a physical system possesses inherent properties that are independent of procedures used to measure them. This issue lies at the core of the famous gedanken experiment of Einstein, Podolsky, and Rosen (EPR) (1) and of attempts to develop a conceptual understanding (2–4) of EPR correlations. Authors: Ebrahim Karimi, Robert W. Boyd

Are we living in a quantum world? Bohr and quantum fundamentalism

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

on 2015-12-03 8:21pm GMT

Zinkernagel, Henrik (2015) Are we living in a quantum world? Bohr and quantum fundamentalism. [Published Article]

Quantum physics: Getting the measure of entanglement

on 2015-12-02 12:00am GMT

A property called entanglement entropy helps to describe the quantum states of interacting particles, and it has at last been measured. The findings open the door to a deeper understanding of quantum systems. See Article p.77

Nature 528 48 doi: 10.1038/528048a

Measuring entanglement entropy in a quantum many-body system

Nature Physical Sciences Research

on 2015-12-02 12:00am GMT

Entanglement is one of the most intriguing features of quantum mechanics. It describes non-local correlations between quantum objects, and is at the heart of quantum information sciences. Entanglement is now being studied in diverse fields ranging from condensed matter to quantum gravity. However, measuring entanglement remains a challenge. This is especially so in systems of interacting delocalized particles, for which a direct experimental measurement of spatial entanglement has been elusive. Here, we measure entanglement in such a system of itinerant particles using quantum interference of many-body twins. Making use of our single-site-resolved control of ultracold bosonic atoms in optical lattices, we prepare two identical copies of a many-body state and interfere them. This enables us to directly measure quantum purity, Rényi entanglement entropy, and mutual information. These experiments pave the way for using entanglement to characterize quantum phases and dynamics of strongly correlated many-body systems.

Nature 528 77 doi: 10.1038/nature15750

Can Many-Valued Logic Help to Comprehend Quantum Phenomena?

Latest Results for International Journal of Theoretical Physics

on 2015-12-01 12:00am GMT

**Abstract**

Following Łukasiewicz, we argue that future non-certain events should be described with the use of many-valued, not 2-valued logic. It is shown that, according to this perspective, the Greenberger – Horne – Zeilinger ‘paradox’ is an artifact caused by unjustified use of 2-valued logic while considering results of future non-certain events. Description of properties of quantum objects before they are measured should be performed with the use of propositional functions that form a particular model of *∞*-valued Łukasiewicz logic. This model is distinguished by specific operations of negation, conjunction, and disjunction that are used in it.

Space and Time in a Quantized World

Latest Results for International Journal of Theoretical Physics

on 2015-12-01 12:00am GMT

**Abstract**

Rather than consider space-time as an *a priori* arena in which events take place, it is a construction of our mind making possible a particular kind of ordering of events. As quantum entanglement is a property of states independent of classical distances, the notion of space and time has to be revised to represent the holistic interconnectedness of quanta. We also speculate about various forms of reprogramming, or reconfiguring, the propagation of information for multipartite statistics and in quantum field theory.

Fuzzy Topology and Geometric Formalism of Quantum Mechanics

Latest Results for International Journal of Theoretical Physics

on 2015-12-01 12:00am GMT

**Abstract**

Dodson-Zeeman fuzzy topology considered as the possible mathematical framework of quantum geometric formalism. In such formalism the states of massive particle *m* correspond to elements of fuzzy manifold called fuzzy points. Due to their weak (partial) ordering, *m* space coordinate *x* acquires principal uncertainty *σ* _{x}_{ }. It’s shown that *m* evolution on such manifold corresponds to quantum dynamics. It’s argued also that particle’s interactions on such fuzzy manifold should be gauge invariant.

A Comparison Between Models of Gravity Induced Decoherence

Latest Results for Foundations of Physics

on 2015-12-01 12:00am GMT

**Abstract**

It has been suggested in the literature that spatial coherence of the wave function can be dynamically suppressed by fluctuations in the spacetime geometry. These fluctuations represent the minimal uncertainty that is present when one probes spacetime geometry with a quantum probe. Two similar models have been proposed, one by Diósi (D-model) and one by Karolyhazy and collaborators (K-model), based on apparently unrelated minimal spacetime bounds. The two models arrive at somewhat different expressions for the dependence of the localization coherence length on the mass and size of the quantum object. In the present article we compare and contrast the two models from three aspects: (i) comparison of the spacetime bounds, (ii) method of calculating decoherence time, (iii) comparison of noise correlation. We show that under certain conditions the minimal spacetime bounds in the two models can be derived one from the other. We argue that the methods of calculating the decoherence time are equivalent. We re-derive the two-point correlation for the fluctuation potential in the K-model, and confirm the earlier result of Diósi and Lukács that it is non-white noise, unlike in the D-model, where the corresponding correlation is white noise in time. This seems to be the origin of the different results in the two models. We derive the non-Markovian master equation for the K-model. We argue that the minimal spacetime bound cannot predict the noise correlation uniquely, and additional criteria are necessary to accurately determine the effects of gravitationally induced decoherence.

Dependence of the Time-Reading Process of the Salecker–Wigner Quantum Clock on the Size of the Clock

Latest Results for Foundations of Physics

on 2015-12-01 12:00am GMT

**Abstract**

It is shown in the present note that the degree of the complexity of the time-reading process of the Salecker–Wigner clock depends on the size of the clock. This dependence leads to a relation between the size and the accuracy of the clock, and suggests a precise optimal value for the size in agreement with the order of magnitude value established by Salecker and Wigner.

On the Importance of Interpretation in Quantum Physics: A Reply to Elise Crull

Latest Results for Foundations of Physics

on 2015-12-01 12:00am GMT

**Abstract**

Elise Crull (Found Phys. doi:10.1007/s10701-014-9847-4, 2014) claims that by invoking decoherence it is possible (i) to obviate many “fine grained” issues often conflated under the common designation of measurement problem, and (ii) to make substantial progresses in the fields of quantum gravity and quantum cosmology, without any early incorporation of a particular interpretation in the quantum formalism. We point out that Crull is mistaken about decoherence and tacitly assumes some kind of interpretation of the quantum formalism.