# Weekly Papers on Quantum Foundations (8)

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

Killer collapse: empirically probing the philosophically unsatisfactory region of GRW

Latest Results for Synthese

on 2015-2-21 12:00am GMT

Abstract

GRW theory offers precise laws for the collapse of the wave function. These collapses are characterized by two new constants, $$\lambda$$ and $$\sigma$$ . Recent work has put experimental upper bounds on the collapse rate, $$\lambda$$ . Lower bounds on $$\lambda$$ have been more controversial since GRW begins to take on a many-worlds character for small values of $$\lambda$$ . Here I examine GRW in this odd region of parameter space where collapse events act as natural disasters that destroy branches of the wave function along with their occupants. Our continued survival provides evidence that we don’t live in a universe like that. I offer a quantitative analysis of how such evidence can be used to assess versions of GRW with small collapse rates in an effort to move towards more principled and experimentally-informed lower bounds for $$\lambda$$ .

The Montevideo Interpretation of Quantum Mechanics: a short review

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

on 2015-2-19 9:55pm GMT

Gambini, Rodolfo and Pullin, Jorge (2015) The Montevideo Interpretation of Quantum Mechanics: a short review. [Preprint]

Quantum Superpositions Do Exist! But ‘Quantum Physical Reality ≠ Actuality’ (Reply to Dieks and Griffiths)

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

on 2015-2-19 9:54pm GMT

de Ronde, Christian (2015) Quantum Superpositions Do Exist! But ‘Quantum Physical Reality ≠ Actuality’ (Reply to Dieks and Griffiths). [Preprint]

Hilbert Space Quantum Mechanics is Contextual (Reply to R. B. Griffiths)

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

on 2015-2-19 9:49pm GMT

de Ronde, Christian (2015) Hilbert Space Quantum Mechanics is Contextual (Reply to R. B. Griffiths). [Preprint]

Direct Tests of Measurement Uncertainty Relations: What It Takes

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

on 2015-2-19 3:00pm GMT

Author(s): Paul Busch and Neil Stevens

The uncertainty principle being a cornerstone of quantum mechanics, it is surprising that, in nearly 90 years, there have been no direct tests of measurement uncertainty relations. This lacuna was due to the absence of two essential ingredients: appropriate measures of measurement error (and disturb…

[Phys. Rev. Lett. 114, 070402] Published Thu Feb 19, 2015

Symmetry as a foundational concept in Quantum Mechanics. (arXiv:1502.05339v1 [quant-ph])

on 2015-2-19 4:22am GMT

Authors: Houri Ziaeepour

Symmetries are widely used in modeling quantum systems but they do not contribute in postulates of quantum mechanics. Here we argue that logical, mathematical, and observational evidence require that symmetry should be considered as a fundamental concept in the construction of physical systems. Based on this idea, we propose a series of postulates for describing quantum systems, and establish their relation and correspondence with axioms of standard quantum mechanics. Through some examples we show that this reformulation helps better understand some of ambiguities of standard description. Nonetheless its application is not limited to explaining confusing concept and it may be a necessary step toward a consistent model of quantum cosmology and gravity.

The essence of nonclassicality: more effect than cause. (arXiv:1502.05390v1 [quant-ph])

on 2015-2-19 4:21am GMT

Authors: S. AravindaR. Srikanth

Nonclassical properties of correlations– like unpredictability, no-cloning and uncertainty– are known to follow from two assumptions: nonlocality and no-signaling. For two-input-two-output correlations, we derive these properties from a single, unified assumption: namely, the excess of the communication cost over the signaling in the correlation. This is relevant to quantum temporal correlations, resources to simulate quantum correlations and extensions of quantum mechanics. We generalize in the context of such correlations the nonclassicality result for nonlocal-nonsignaling correlations (Masanes, Acin and Gisin, 2006) and the uncertainty bound on nonlocality (Oppenheim and Wehner, 2010), when the no-signaling condition is relaxed. An analogy of nonclassicality with G\”odel incompleteness is suggested, motivated by the expectation that quantum unpredictability is somehow comparable with metamathematical undecidability. This line of research could shed light on why randomness may be inevitable in Nature.

Local reversibility and entanglement structure of many-body ground states. (arXiv:1502.05330v1 [quant-ph])

on 2015-2-19 4:21am GMT

The low-temperature physics of quantum many-body systems is largely governed by the structure of their ground states. Minimizing the energy of local interactions, ground states often reflect strong properties of locality such as the area law for entanglement entropy and the exponential decay of correlations between spatially separated observables. In this letter we present a novel characterization of locality in quantum states, which we call `local reversibility’. It characterizes the type of operations that are needed to reverse the action of a general disturbance on the state. We prove that unique ground states of gapped local Hamiltonian are locally reversible. This way, we identify new fundamental features of many-body ground states, which cannot be derived from the aforementioned properties. We use local reversibility to distinguish between states enjoying microscopic and macroscopic quantum phenomena. To demonstrate the potential of our approach, we prove specific properties of ground states, which are relevant both to critical and non-critical theories.

Quantum Superpositions Do Exist! But ‘Quantum Physical Reality is different to Actuality’ (Reply to Dieks and Griffiths). (arXiv:1502.05311v1 [quant-ph])

on 2015-2-19 4:21am GMT

Authors: Christian de Ronde

In this paper we analyze the definition of quantum superpositions within orthodox Quantum Mechanics (QM) and their relation to physical reality. We will begin by discussing how the metaphysical presuppositions imposed by Bohr on the interpretation of QM have become not only interpretational dogmas which constrain the limits of the present Orthodox Line of Research (OLR), but also how these desiderata implicitly preclude the possibility of developing a physical representation of quantum superpositions. We will then continue analyzing how most interpretations of QM argue against the existence of superpositions. Firstly, we will focus on those interpretations which attempt to recover a classical representation about “what there is”, and secondly, we will concentrate on the arguments provided by Dieks and Griffiths who, staying close to the orthodox formalism, also attempt to “get rid of the ghost of Schrodinger’s cat”. Contrary to the OLR, we will argue -based on our definition of Meaningful Physical Statements (MPS)- that from a representational realist perspective which stays close to the orthodox Hilbert space formalism, quantum superpositions are not only the key to the most important -present and future- technological and experimental developments in quantum information processing but also, they must be considered as the kernel of any interpretation of QM that attempts to provide a physical representation of reality. We will also argue that the price to pay for such representational realist development must be the abandonment of the (dogmatic) idea that ‘Actuality = Reality’.

Modality, Potentiality and Contradiction in Quantum Mechanics. (arXiv:1502.05081v1 [quant-ph])

on 2015-2-19 4:21am GMT

Authors: Christian de Ronde

In [11], Newton da Costa together with the author of this paper argued in favor of the possibility to consider quantum superpositions in terms of a paraconsistent approach. We claimed that, even though most interpretations of quantum mechanics (QM) attempt to escape contradictions, there are many hints that indicate it could be worth while to engage in a research of this kind. Recently, Arenhart and Krause [1, 2, 3] have raised several arguments against this approach and claimed that, taking into account the square of opposition, quantum superpositions are better understood in terms of contrariety propositions rather than contradictory propositions. In [17] we defended the Paraconsistent Approach to Quantum Superpositions (PAQS) and provided arguments in favor of its development. In the present paper we attempt to analyze the meanings of modality, potentiality and contradiction in QM, and provide further arguments of why the PAQS is better suited, than the Contrariety Approach to Quantum Superpositions (CAQS) proposed by Arenhart and Krause, to face the interpretational questions that quantum technology is forcing us to consider.

The utility of Naturalness, and how its application to Quantum Electrodynamics envisages the Standard Model and Higgs boson

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

on 2015-2-18 6:52pm GMT

Publication date: February 2015
Source:Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics, Volume 49
Author(s): James D. Wells
With the Higgs boson discovery and no new physics found at the LHC, confidence in Naturalness as a guiding principle for particle physics is under increased pressure. We wait to see if it proves its mettle in the LHC upgrades ahead, and beyond. In the meantime, I present a justification a posteriori of the Naturalness criterion by suggesting that uncompromising application of the principle to Quantum Electrodynamics leads toward the Standard Model and Higgs boson without additional experimental input. Potential lessons for today and future theory building are commented upon.

Quantum fields in curved spacetime

ScienceDirect Publication: Physics Reports

on 2015-2-18 1:16pm GMT

Publication date: Available online 14 February 2015
Source:Physics Reports
Author(s): Stefan Hollands , Robert M. Wald
We review the theory of quantum fields propagating in an arbitrary, classical, globally hyperbolic spacetime. Our review emphasizes the conceptual issues arising in the formulation of the theory and presents known results in a mathematically precise way. Particular attention is paid to the distributional nature of quantum fields, to their local and covariant character, and to microlocal spectrum conditions satisfied by physically reasonable states. We review the Unruh and Hawking effects for free fields, as well as the behavior of free fields in deSitter spacetime and FLRW spacetimes with an exponential phase of expansion. We review how nonlinear observables of a free field, such as the stress–energy tensor, are defined, as well as time-ordered-products. The “renormalization ambiguities” involved in the definition of time-ordered products are fully characterized. Interacting fields are then perturbatively constructed. Our main focus is on the theory of a scalar field, but a brief discussion of gauge fields is included. We conclude with a brief discussion of a possible approach towards a nonperturbative formulation of quantum field theory in curved spacetime and some remarks on the formulation of quantum gravity.

Timelines and Quantum Time Operators

Latest Results for Foundations of Physics

on 2015-2-18 12:00am GMT

Abstract

The failure of conventional quantum theory to recognize time as an observable and to admit time operators is addressed. Instead of focusing on the existence of a time operator for a given Hamiltonian, we emphasize the role of the Hamiltonian as the generator of translations in time to construct time states. Taken together, these states constitute what we call a timeline. Such timelines are adequate for the representation of any physical state, and appear to exist even for the semi-bounded and discrete Hamiltonian systems ruled out by Pauli’s theorem. However, the step from a timeline to a valid time operator requires additional assumptions that are not always met. Still, this approach illuminates the issues surrounding the construction of time operators, and establishes timelines as legitimate alternatives to the familiar coordinate and momentum bases of standard quantum theory.

Why I am not a QBist

Latest Results for Foundations of Physics

on 2015-2-18 12:00am GMT

Abstract

Quantum Bayesianism, or QBism, is a recent development of the epistemic view of quantum states, according to which the state vector represents knowledge about a quantum system, rather than the true state of the system. QBism explicitly adopts the subjective view of probability, wherein probability assignments express an agent’s personal degrees of belief about an event. QBists claim that most if not all conceptual problems of quantum mechanics vanish if we simply take a proper epistemic and probabilistic perspective. Although this judgement is largely subjective and logically consistent, I explain why I do not share it.

Nonclassicality tests and entanglement witnesses for macroscopic mechanical superposition states

PRA: Fundamental concepts

on 2015-2-17 3:00pm GMT

Author(s): Oleg Gittsovich, Tobias Moroder, Ali Asadian, Otfried Gühne, and Peter Rabl

We describe a set of measurement protocols for performing nonclassicality tests and the verification of entangled superposition states of macroscopic continuous variable systems, such as nanomechanical resonators. Following earlier works, we first consider a setup where a two-level system is used to…

[Phys. Rev. A 91, 022114] Published Tue Feb 17, 2015

Dynamical Casimir effect and minimal temperature in quantum thermodynamics

PRA Rapid Communications

on 2015-2-17 3:00pm GMT

Author(s): Giuliano Benenti and Giuliano Strini

We study the fundamental limitations of cooling to absolute zero for a qubit, interacting with a single mode of the electromagnetic field. Our results show that the dynamical Casimir effect, which is unavoidable in any finite-time thermodynamic cycle, forbids the attainability of the absolute zero o…

[Phys. Rev. A 91, 020502] Published Tue Feb 17, 2015