Publication date: Available online 14 August 2020

Source: Physics Reports

Author(s): T. Aoyama, N. Asmussen, M. Benayoun, J. Bijnens, T. Blum, M. Bruno, I. Caprini, C.M. Carloni Calame, M. Cè, G. Colangelo, F. Curciarello, H. Czyż, I. Danilkin, M. Davier, C.T.H. Davies, M. Della Morte, S.I. Eidelman, A.X. El-Khadra, A. Gérardin, D. Giusti

In this paper we consider a new geometric approach to Madelung’s quantum hydrodynamics (QHD) based on the theory of gauge connections. Unlike previous approaches, our treatment comprises a constant curvature thereby endowing QHD with intrinsic non-zero holonomy. In the hydrodynamic context, this leads to a fluid velocity which no longer is constrained to be irrotational and allows instead for vortex filaments solutions. After exploiting the Rasetti-Regge method to couple the Schr\”odinger equation to vortex filament dynamics, the latter is then considered as a source of geometric phase in the context of Born-Oppenheimer molecular dynamics. Similarly, we consider the Pauli equation for the motion of spin particles in electromagnetic fields and we exploit its underlying hydrodynamic picture to include vortex dynamics.

Quantum information science is an exciting, wide, rapidly progressing, cross-disciplinary field, and that very nature makes it both attractive and hard to enter. In this primer, we first provide answers to the three essential questions that any newcomer needs to know: How is quantum information represented? How is quantum information processed? How is classical information extracted from quantum states? We then introduce the most basic quantum information theoretic notions concerning entropy, sources, and channels, as well as secure communications and error correction. We conclude with examples that illustrate the power of quantum correlations. No prior knowledge of quantum mechanics is assumed.

We study the holographic map in AdS/CFT, as modeled by a quantum error correcting code with exact complementary recovery. We show that the map is determined by local conditional expectations acting on the operator algebras of the boundary/physical Hilbert space. Several existing results in the literature follow easily from this perspective. The Black Hole area law, and more generally the Ryu-Takayanagi area operator, arises from a central sum of entropies on the relative commutant. These entropies are determined in a state independent way by the conditional expectation. The conditional expectation can also be found via a minimization procedure, similar to the minimization involved in the RT formula. For a local net of algebras associated to connected boundary regions, we show the complementary recovery condition is equivalent to the existence of a standard net of inclusions — an abstraction of the mathematical structure governing QFT superselection sectors given by Longo and Rehren. For a code consisting of algebras associated to two disjoint regions of the boundary theory we impose an extra condition, dubbed dual-additivity, that gives rise to phase transitions between different entanglement wedges. Dual-additive codes naturally give rise to a new split code subspace, and an entropy bound controls which subspace and associated algebra is reconstructable. We also discuss known shortcomings of exact complementary recovery as a model of holography. For example, these codes are not able to accommodate holographic violations of additive for overlapping regions. We comment on how approximate codes can fix these issues.

In this work we consider a wide variety of alternatives opened when applying the continuous spontaneous localization (CSL) dynamical collapse theory to the inflationary era. This exploration includes: two different approaches to deal with quantum field theory and gravitation, the identification of the collapse-generating operator and the general nature and values of the parameters of the CSL theory. All the choices connected with these issues have the potential to dramatically alter the conclusions one can draw. We also argue that the incompatibilities found in a recent paper, between the CSL parameter values and the CMB observational data, are associated with specific choices made for the extrapolation to the cosmological context of the CSL theory (as it is known to work in non-relativistic laboratory situations) which do not represent the most natural ones.

Authors: Rabin Banerjee

We discuss a new formalism for constructing a non-relativistic (NR) theory in curved background. Named as galilean gauge theory, it is based on gauging the global galilean symmetry. It provides a systematic algorithm for obtaining the covariant curved space time generalisation of any NR theory defined in flat space time. The resulting background is just the Newton- Cartan manifold. The example of NR free particle is explicitly demonstrated.

Authors: Lavinia Heisenberg, Jann Zosso

We establish radiative stability of all generalized Proca theories. While standard powercounting arguments would conclude otherwise, we find non-trivial cancellations of leading order corrections by explicit computation of divergent one-loop diagrams up to four-point. These results are crosschecked against an effective action based generalized Schwinger-DeWitt method. Further, these cancellations are understood as coming from the specific structure of the theory through a decoupling limit analysis which at the same time allows for an extension of the results to all orders.

Fernández Mouján, Raimundo (2020) Greek philosophy for quantum physics. The return to the Greeks in the works of Heisenberg, Pauli and Schrödinger. [Preprint]

Abstract

Remember how Kim (Philos Perspect 3:77–108, 1989, in: Heil and Mele (eds) Mental causation, Clarendon Press, Oxford, 1993b) used to argue against non-reductive physicalism to the effect that it cannot accommodate the causal efficacy of the mental? The argument was that if physicalists accept the causal closure of the physical, they are faced with an exclusion problem. In the original version of the argument, the dependence holding between the mental and the physical was cashed out in terms of supervenience. Due to the work or Fine (Philos Perspect 8:1–16, 1994) and others, we have since come to realize that modal notions are not well-suited to perform the work of properly characterizing dependence. As a consequence of this, an increasingly larger community of contemporary metaphysicians prefer to spell out mental-physical dependence in terms of a non-causal and non-reductive notion called grounding, which is intended to target a particular sort of metaphysical relation that takes us from ontologically less fundamental features of the world to that which is more fundamental. In this paper I join forces with those who think that this shift in focus is on the right track. More specifically, I will argue that the grounding physicalist can solve the exclusion problem in a way that is preferable to the supervenience-based nonreductive physicalist solution, as well as in a way that is compatible with the externalist picture of the mental.

Stuart, Michael T. (2021) Telling Stories in Science: Feyerabend and Thought Experiments. [Preprint]

Abstract

This essay is concerned with a number of related proposals that claim there is a link between spacetime topology and quantum entanglement. I indicate the extent to which these proposals can be understood as stating a duality, and then consider two general approaches to articulating such a duality: a “state-based” approach, under which one attempts to identify relevant topological states as dual to quantum entangled states; and an “observable-based” approach, under which one attempts to identify relevant topological observables as dual to quantum entangement observables. Both approaches are faced with issues, essentially due to the ambiguous nature of quantum entanglement, that remain to be addressed.

Lehmkuhl, Dennis (2019) The Equivalence Principle(s). [Preprint]

Callender, Craig (2020) Quantum Mechanics: Keeping It Real? [Preprint]

Abstract

Many non-physicalists, including Chalmers, hold that the zombie argument succeeds in rejecting the physicalist view of consciousness. Some non-physicalists, including, again, Chalmers, hold that quantum collapse interactionism (QCI), i.e., the idea that non-physical consciousness causes collapse of the wave function in phenomena such as quantum measurement, is a viable interactionist solution for the problem of the relationship between the physical world and the non-physical consciousness. In this paper, I argue that if QCI is true, the zombie argument fails. In particular, I show that if QCI is true, a zombie world physically identical to our world is impossible because there is at least one law of nature, a fundamental law of physics in particular, that exist only in the zombie world but not in our world. This shows that philosophers like Chalmers are committing an error in endorsing the zombie argument and QCI at the same time.

Author(s): David Felce and Vlatko Vedral

We propose a thermodynamic refrigeration cycle which uses indefinite causal orders to achieve nonclassical cooling. The cycle cools a cold reservoir while consuming purity in a control qubit. We first show that the application to an input state of two identical thermalizing channels of temperature T…

[Phys. Rev. Lett. 125, 070603] Published Tue Aug 11, 2020

Nature Physics, Published online: 10 August 2020; doi:10.1038/s41567-020-0992-8

A protocol for the reliable, efficient and precise characterization of quantum noise is reported and implemented in an architecture consisting of 14 superconducting qubits. Correlated noise within arbitrary sets of qubits can be easily detected.

Abstract

While there has been much discussion about what makes some mathematical proofs more explanatory than others, and what are mathematical coincidences, in this article I explore the distinct phenomenon of mathematical facts that call for explanation. The existence of mathematical facts that call for explanation stands in tension with virtually all existing accounts of “calling for explanation”, which imply that necessary facts cannot call for explanation. In this paper I explore what theoretical revisions are needed in order to accommodate this phenomenon. One of the important upshots is that, contrary to the current consensus, low prior probability is not a necessary condition for calling for explanation. In the final section I explain how the results of this inquiry help us make progress in assessing Hartry Field’s style of reliability argument against mathematical Platonism and against robust realism in other domains of necessary facts, such as ethics.

Johnson, Jack (2019) Probability and Coincidence in Time Travel Scenarios. [Preprint]