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.

Experimental Test of Hyper-Complex Quantum Theories. (arXiv:1602.01624v1 [quant-ph])

on 2016-2-06 6:21am GMT

Authors: Lorenzo M. Procopio, Lee A. Rozema, Zi Jing Wong, Deny R. Hamel, Kevin O’Brien, Xiang Zhang, Borivoje Dakic, Philip Walther

In standard quantum mechanics, complex numbers are used to describe the wavefunction. Although complex numbers have proven sufficient to predict the results of existing experiments, there is no apparent theoretical reason to choose them over real numbers or generalizations of complex numbers, i.e. hyper-complex numbers. Experiments performed to date have proven that real numbers are insufficient, but whether or not hyper-complex numbers are required remains an open question. Quantum theories based on hyper-complex numbers are one example of a post-quantum theory, which must be put on a firm experimental foundation. Here we experimentally probe hyper-complex quantum theories, by studying one of their deviations from complex quantum theory: the non-commutativity of phases. We do so by passing single photons through a Sagnac interferometer containing two physically different phases, having refractive indices of opposite sign. By showing that the phases commute with high precision, we place limits on a particular prediction of hyper-complex quantum theories.

Time Really Passes, Science Can’t Deny That. (arXiv:1602.01497v1 [quant-ph])

on 2016-2-01 8:11am GMT

Authors: Nicolas Gisin

Today’s science provides quite a lean picture of time as a mere geometric evolution parameter. I argue that time is much richer. In particular, I argue that besides the geometric time, there is creative time, when objective chance events happen. The existence of the latter follows straight from the existence of free-will. Following the french philosopher Lequyer, I argue that free-will is a prerequisite for the possibility to have rational argumentations, hence can’t be denied. Consequently, science can’t deny the existence of creative time and thus that time really passes.

on 2016-2-06 4:56am GMT

Publication date: February 2016

**Source:**Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics, Volume 53

Author(s): Lina Jansson

Everettian quantum mechanics faces the challenge of how to make sense of probability and probabilistic reasoning in a setting where there is typically no unique outcome of measurements. Wallace has built on a proof by Deutsch to argue that a notion of probability can be recovered in the many worlds setting. In particular, Wallace argues that a rational agent has to assign probabilities in accordance with the Born rule. This argument relies on a rationality constraint that Wallace calls state supervenience. I argue that state supervenience is not defensible as a rationality constraint for Everettian agents unless we already invoke probabilistic notions.

Propensity, Probability, and Quantum Theory

Latest Results for Foundations of Physics

on 2016-2-04 12:00am GMT

**Abstract**

Quantum mechanics and probability theory share one peculiarity. Both have well established mathematical formalisms, yet both are subject to controversy about the meaning and interpretation of their basic concepts. Since probability plays a fundamental role in QM, the conceptual problems of one theory can affect the other. We first classify the interpretations of probability into three major classes: (a) *inferential probability*, (b) *ensemble probability*, and (c) *propensity*. Class (a) is the basis of inductive logic; (b) deals with the frequencies of events in repeatable experiments; (c) describes a form of causality that is weaker than determinism. An important, but neglected, paper by P. Humphreys demonstrated that *propensity* must differ *mathematically*, as well as conceptually, from probability, but he did not develop a theory of propensity. Such a theory is developed in this paper. Propensity theory shares many, but not all, of the axioms of probability theory. As a consequence, *propensity* supports the *Law of Large Numbers* from probability theory, but does not support *Bayes theorem*. Although there are particular problems within QM to which any of the classes of probability may be applied, it is argued that the intrinsic *quantum probabilities* (calculated from a state vector or density matrix) are most naturally interpreted as *quantum propensities*. This does not alter the familiar *statistical interpretation* of QM. But the interpretation of quantum states as representing *knowledge* is untenable. Examples show that a density matrix fails to represent knowledge.

Conservation of information and the foundations of quantum mechanics

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

on 2016-2-03 7:02am GMT

Chiribella, Giulio and Scandolo, Carlo Maria (2015) Conservation of information and the foundations of quantum mechanics. [Published Article]

Jerusalem lectures on black holes and quantum information

Recent Articles in Rev. Mod. Phys.

on 2016-2-02 3:00pm GMT

Author(s): D. Harlow

The quantum mechanics of black holes, and particularly the information paradox, have been a crucial arena for testing theories of quantum gravity. This review covers the quantum physics of black holes, anti-de Sitter/conformal field theory duality and holography, and the recent firewall paradox, with a focus on ideas from quantum information theory.

[Rev. Mod. Phys. 88, 015002] Published Tue Feb 02, 2016

Generalized Lagrangian-Path Representation of Non-Relativistic Quantum Mechanics

Latest Results for Foundations of Physics

on 2016-2-02 12:00am GMT

**Abstract**

In this paper a new trajectory-based representation to non-relativistic quantum mechanics is formulated. This is ahieved by generalizing the notion of Lagrangian path (LP) which lies at the heart of the deBroglie-Bohm “ pilot-wave” interpretation. In particular, it is shown that each LP can be replaced with a statistical ensemble formed by an infinite family of stochastic curves, referred to as generalized Lagrangian paths (GLP). This permits the introduction of a new parametric representation of the Schrödinger equation, denoted as GLP-parametrization, and of the associated quantum hydrodynamic equations. The remarkable aspect of the GLP approach presented here is that it realizes at the same time also a new solution method for the *N*-body Schrödinger equation. As an application, Gaussian-like particular solutions for the quantum probability density function (PDF) are considered, which are proved to be dynamically consistent. For them, the Schrödinger equation is reduced to a single Hamilton–Jacobi evolution equation. Particular solutions of this type are explicitly constructed, which include the case of free particles occurring in 1- or *N*-body quantum systems as well as the dynamics in the presence of suitable potential forces. In all these cases the initial Gaussian PDFs are shown to be free of the spreading behavior usually ascribed to quantum wave-packets, in that they exhibit the characteristic feature of remaining at all times spatially-localized.

Philosophy of Quantum Probability – An empiricist study of its formalism and logic

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

on 2016-2-01 7:24pm GMT

Hermens, Ronnie (2016) Philosophy of Quantum Probability – An empiricist study of its formalism and logic. UNSPECIFIED.

Contexts, Systems and Modalities: A New Ontology for Quantum Mechanics

Latest Results for Foundations of Physics

on 2016-2-01 12:00am GMT

**Abstract**

In this article we present a possible way to make usual quantum mechanics fully compatible with physical realism, defined as the statement that the goal of physics is to study entities of the natural world, existing independently from any particular observer’s perception, and obeying universal and intelligible rules. Rather than elaborating on the quantum formalism itself, we propose a new quantum ontology, where physical properties are attributed jointly to the system, and to the context in which it is embedded. In combination with a quantization principle, this non-classical definition of physical reality sheds new light on counter-intuitive features of quantum mechanics such as the origin of probabilities, non-locality, and the quantum-classical boundary.

The Measurement Process in the Generalized Contexts Formalism for Quantum Histories

Latest Results for International Journal of Theoretical Physics

on 2016-2-01 12:00am GMT

**Abstract**

In the interpretations of quantum mechanics involving quantum histories there is no collapse postulate and the measurement is considered as a quantum interaction between the measured system and the measured instrument. For two consecutive non ideal measurements on the same system, we prove that both pointer indications at the end of each measurement are compatible properties in our generalized context formalism for quantum histories. Inmediately after the first measurement an effective state for the measured system is deduced from the formalism, generalizing the state that would be obtained by applying the state collapse postulate.