# Weekly Papers on Quantum Foundations (45)

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.

Living in a Superposition. (arXiv:1511.01550v1 [quant-ph])

on 2015-11-07 9:22am GMT

Authors: James B. Hartle

This essay considers a model quantum universe consisting of a very large box containing a screen with two slits and an observer (us) that can pass though the slits. We apply the modern quantum mechanics of closed systems to calculate the probabilities for alternative histories of how we move through the universe and what we see. After passing through the screen with the slits, the quantum state of the universe is a superposition of classically distinguishable histories. We are then living in a superposition. Some frequently asked questions about such situations are answered using this model. The model’s relationship to more realistic quantum cosmologies is briefly discussed.

Towards a Paraconsistent Quantum Set Theory. (arXiv:1511.01571v1 [math.LO])

on 2015-11-07 9:22am GMT

Authors: Benjamin Eva (University of Bristol)

In this paper, we will attempt to establish a connection between quantum set theory, as developed by Ozawa, Takeuti and Titani, and topos quantum theory, as developed by Isham, Butterfield and Doring, amongst others. Towards this end, we will study algebraic valued set-theoretic structures whose truth values correspond to the clopen subobjects of the spectral presheaf of an orthomodular lattice of projections onto a given Hilbert space. In particular, we will attempt to recreate, in these new structures, Takeuti’s original isomorphism between the set of all Dedekind real numbers in a suitably constructed model of set theory and the set of all self adjoint operators on a chosen Hilbert space.

Black hole remnants and the information loss paradox

ScienceDirect Publication: Physics Reports

on 2015-11-06 6:04pm GMT

Publication date: Available online 4 November 2015
Source:Physics Reports
Author(s): P. Chen, Y.C. Ong, D-h. Yeom
Forty years after the discovery of Hawking radiation, its exact nature remains elusive. If Hawking radiation does not carry any information out from the ever shrinking black hole, it seems that unitarity is violated once the black hole completely evaporates. On the other hand, attempts to recover information via quantum entanglement lead to the firewall controversy. Amid the confusions, the possibility that black hole evaporation stops with a “remnant” has remained unpopular and is often dismissed due to some “undesired properties” of such an object. Nevertheless, as in any scientific debate, the pros and cons of any proposal must be carefully scrutinized. We fill in the void of the literature by providing a timely review of various types of black hole remnants, and provide some new thoughts regarding the challenges that black hole remnants face in the context of the information loss paradox and its latest incarnation, namely the firewall controversy. The importance of understanding the role of curvature singularity is also emphasized, after all there remains a possibility that the singularity cannot be cured even by quantum gravity. In this context a black hole remnant conveniently serves as a cosmic censor. We conclude that a remnant remains a possible end state of Hawking evaporation, and if it contains large interior geometry, may help to ameliorate the information loss paradox and the firewall controversy. We hope that this will raise some interests in the community to investigate remnants more critically but also more thoroughly.

Reduction and emergence in the fractional quantum Hall state

ScienceDirect Publication: Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics

on 2015-11-06 4:10pm GMT

Publication date: Available online 3 November 2015
Source:Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics
Author(s): Tom Lancaster, Mark Pexton
We present the fractional quantum Hall (FQH) effect as a candidate emergent phenomenon. Unlike some other putative cases of condensed matter emergence (such as thermal phase transitions), the FQH effect is not based on symmetry breaking. Instead FQH states are part of a distinct class of ordered matter that is defined topologically. Topologically ordered states result from complex long-ranged correlations between their constituent parts, such that the system displays strongly irreducible, qualitatively novel properties.

Discovering Quantum Causal Models

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

on 2015-11-04 6:28pm GMT

Shrapnel, Sally (2015) Discovering Quantum Causal Models. [Preprint]

Quantum physics: Quantum sound waves stick together

Nature Physical Sciences Research

on 2015-11-04 12:00am GMT

A sensitive cold-ion experiment probes sound at the level of phonons, the fundamental quantum units of vibration. It shows that phonons mix in such a way that they can be classified as ‘bosonic’ particles, like photons. See Letter p.74

Nature 527 45 doi: 10.1038/527045a

Particle physics after the Higgs discovery: philosophical perspectives

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

on 2015-11-03 9:56pm GMT

Friederich, S. and Lehmkuhl, D. (2015) Particle physics after the Higgs discovery: philosophical perspectives. [Published Article]

Re-thinking local causality

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

on 2015-11-03 9:53pm GMT

Friederich, S. (2015) Re-thinking local causality. [Published Article]

Grover search and the no-signaling principle. (arXiv:1511.00657v1 [quant-ph])

on 2015-11-03 8:48am GMT

Authors: Ning BaoAdam BoulandStephen P. Jordan

From an information processing point of view, two of the key properties of quantum physics are the no-signaling principle and the Grover search lower bound. That is, despite admitting stronger-than-classical correlations, quantum mechanics does not imply superluminal signaling, and despite a form of exponential parallelism, quantum mechanics does not imply polynomial-time brute force solution of NP-complete problems. Here, we investigate the degree to which these two properties are connected. We examine four classes of deviations from quantum mechanics, for which we draw inspiration from the literature on the black hole information paradox: nonunitary dynamics, non-Born-rule measurement, cloning, and postselection. We find that each model admits superluminal signaling if and only if it admits a query complexity speedup over Grover’s algorithm. Furthermore, we show that the physical resources required to send a superluminal signal scale polynomially with the resources needed to speed up Grover’s algorithm. Hence, one can perform a physically reasonable experiment demonstrating superluminal signaling if and only if one can perform a reasonable experiment inducing a speedup over Grover’s algorithm.

Irreversibility and the Arrow of Time in a Quenched Quantum System

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

on 2015-11-02 3:00pm GMT

Author(s): T. B. Batalhão, A. M. Souza, R. S. Sarthour, I. S. Oliveira, M. Paternostro, E. Lutz, and R. M. Serra

Entropy production, a quantity associated with the emergence of the arrow of time, has been successfully measured in a microscopic quantum system.

[Phys. Rev. Lett. 115, 190601] Published Mon Nov 02, 2015

Proof of a Conjecture on Contextuality in Cyclic Systems with Binary Variables

Latest Results for Foundations of Physics

on 2015-11-02 12:00am GMT

Abstract

We present a proof for a conjecture previously formulated by Dzhafarov et al. (Found Phys 7:762–782, 2015). The conjecture specifies a measure for the degree of contextuality and a criterion (necessary and sufficient condition) for contextuality in a broad class of quantum systems. This class includes Leggett–Garg, EPR/Bell, and Klyachko–Can–Binicioglu–Shumovsky type systems as special cases. In a system of this class certain physical properties $$q_{1},\ldots ,q_{n}$$ are measured in pairs $$\left( q_{i},q_{j}\right)$$ ; every property enters in precisely two such pairs; and each measurement outcome is a binary random variable. Denoting the measurement outcomes for a property $$q_{i}$$ in the two pairs it enters by $$V_{i}$$ and $$W_{i}$$ , the pair of measurement outcomes for $$\left( q_{i},q_{j}\right)$$ is $$\left( V_{i},W_{j}\right)$$ . Contextuality is defined as follows: one computes the minimal possible value $$\Delta _{0}$$ for the sum of $$\Pr \left[ V_{i}\not =W_{i}\right]$$ (over $$i=1,\ldots ,n$$ ) that is allowed by the individual distributions of $$V_{i}$$ and $$W_{i}$$ ; one computes the minimal possible value $$\Delta _{\min }$$ for the sum of $$\Pr \left[ V_{i}\not =W_{i}\right]$$ across all possible couplings of (i.e., joint distributions imposed on) the entire set of random variables $$V_{1},W_{1},\ldots ,V_{n},W_{n}$$ in the system; and the system is considered contextual if $$\Delta _{\min }>\Delta _{0}$$ (otherwise $$\Delta _{\min }=\Delta _{0}$$ ). This definition has its justification in the general approach dubbed Contextuality-by-Default, and it allows for measurement errors and signaling among the measured properties. The conjecture proved in this paper specifies the value of $$\Delta _{\min }-\Delta _{0}$$ in terms of the distributions of the measurement outcomes $$\left( V_{i},W_{j}\right)$$ .

Lagrangian Description for Particle Interpretations of Quantum Mechanics: Single-Particle Case

Latest Results for Foundations of Physics

on 2015-11-01 12:00am GMT

Abstract

A Lagrangian description is presented which can be used in conjunction with particle interpretations of quantum mechanics. A special example of such an interpretation is the well-known Bohm model. The Lagrangian density introduced here also contains a potential for guiding the particle. The advantages of this description are that the field equations and the particle equations of motion can both be deduced from a single Lagrangian density expression and that conservation of energy and momentum are assured. After being developed in a general form, this Lagrangian formulation is then applied to the special case of the Bohm model as an example. It is thereby demonstrated that such a Lagrangian description is compatible with the predictions of quantum mechanics.

Wave–Particle Duality: An Information-Based Approach

Latest Results for Foundations of Physics

on 2015-11-01 12:00am GMT

Abstract

Recently, Bohr’s complementarity principle was assessed in setups involving delayed choices. These works argued in favor of a reformulation of the aforementioned principle so as to account for situations in which a quantum system would simultaneously behave as wave and particle. Here we defend a framework that, supported by well-known experimental results and consistent with the decoherence paradigm, allows us to interpret complementarity in terms of correlations between the system and an informer. Our proposal offers formal definition and operational interpretation for the dual behavior in terms of both nonlocal resources and the couple work-information. Most importantly, our results provide a generalized information-based trade-off for the wave–particle duality and a causal interpretation for delayed-choice experiments.