# Weekly Papers on Quantum Foundations (46)

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

Waiting for the quantum bus: The flow of negative probability

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

on 2014-11-15 10:51am GMT

Publication date: November 2014
Source:Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics, Volume 48, Part A
Author(s): A.J. Bracken , G.F. Melloy
It is 45 years since the discovery of the peculiar quantum effect known as ‘probability backflow’, and it is 20 years since the greatest possible size of the effect was characterized. Recently an experiment has been proposed to observe it directly, for the first time, by manipulating ultra-cold atoms. Here a non-technical description is given of the effect and its interpretation in terms of the flow of negative probability.

Time in fundamental physics

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

on 2014-11-15 10:51am GMT

Publication date: Available online 3 October 2014
Source:Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics
Author(s): Abhay Ashtekar
The first three sections of this paper contain a broad brush summary of the profound changes in the notion of time in fundamental physics that were brought about by three revolutions: the foundations of mechanics distilled by Newton in his Principia, the discovery of special relativity by Einstein and its reformulation by Minkowski, and, finally, the fusion of geometry and gravity in Einstein׳s general relativity. The fourth section discusses two aspects of yet another deep revision that waits in the wings as we attempt to unify general relativity with quantum physics.

A categorial approach to relativistic locality

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

on 2014-11-15 10:51am GMT

Publication date: Available online 26 September 2014
Source:Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics
Author(s): Miklós Rédei
Relativistic locality is interpreted in this paper as a web of conditions expressing the compatibility of a physical theory with the underlying causal structure of spacetime. Four components of this web are distinguished: spatiotemporal locality, along with three distinct notions of causal locality, dubbed CL-Independence, CL-Dependence, and CL-Dynamic. These four conditions can be regimented using concepts from the categorical approach to quantum field theory initiated by Brunetti, Fredenhagen, and Verch (2003). A covariant functor representing a general quantum field theory is defined to be causally local if it satisfies the three CL conditions. Any such theory is viewed as fully compliant with relativistic locality. We survey current results indicating the extent to which an algebraic quantum field theory satisfying the Haag–Kastler axioms is causally local.

Berry phase and quantum structure

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

on 2014-11-15 10:51am GMT

Publication date: November 2014
Source:Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics, Volume 48, Part A
Author(s): Holger Lyre
The paper aims to spell out the relevance of the Berry phase in view of the question what the minimal mathematical structure is that accounts for all observable quantum phenomena. The question is both of conceptual and of ontological interest. While common wisdom tells us that the quantum structure is represented by the structure of the projective Hilbert space, the appropriate structure rich enough to account for the Berry phase is the U(1) bundle over that projective space. The Berry phase is ultimately rooted in the curvature of this quantum bundle, it cannot be traced back to the Hamiltonian dynamics alone. This motivates the ontological claim in the final part of the paper that, if one strives for a realistic understanding of quantum theory including the Berry phase, one should adopt a form of ontic structural realism.

Coherent versus Measurement Feedback: Linear Systems Theory for Quantum Information

Recent Articles in Phys. Rev. X

on 2014-11-14 3:00pm GMT

Author(s): Naoki Yamamoto

Deciding whether to conduct a measurement is a fundamental tenant of quantum physics. A new analysis finds situations in the linear regime where measurement-based feedback control of a quantum system has no merit.

[Phys. Rev. X 4, 041029] Published Fri Nov 14, 2014

Observability of the scalar Aharonov-Bohm effect inside a 3D Faraday cage with time-varying exterior charges and masses. (arXiv:1411.3627v1 [quant-ph])

on 2014-11-14 9:23am GMT

In this paper we investigate the scalar Aharonov-Bohm (AB) effect in two of its forms, i.e., its electric form and its gravitational form. The standard form of the electric AB effect involves having particles (such as electrons) move in regions with zero electric field but different electric potentials. When a particle is recombined with itself, it will have a different phase, which can show up as a change in the way the single particle interferes with itself when it is recombined with itself. In the case where one has quasi-static fields and potentials, the particle will invariably encounter fringing fields, which makes the theoretical and experimental status of the electric AB effect much less clear than that of the magnetic (or vector) AB effect. Here we propose using time varying fields outside of a spherical shell, and potentials inside a spherical shell to experimentally test the scalar AB effect. In our proposal a quantum system will always be in a field-free region but subjected to a non-zero time-varying potentials. Furthermore, our system will not be spatially split and brought back together as in the magnetic AB experiment. Therefore there is no spatial interference and hence no shift in a spatial interference pattern to observe. Rather, there arises purely temporal interference phenomena. As in the magnetic AB experiments, these effects are non-classical. We present two versions of this idea: (i) a Josephson temporal interferometry experiment inside a superconducting spherical shell with a time-varying surface charge; (ii) a two-level atom experiment in which the atomic spectrum acquires FM sidebands when it is placed inside a spherical shell whose exterior mass is sinusoidally varying with time. The former leads to a time-varying internal magnetic field, and the latter leads to a time-varying gravitational redshift.

Projective Limits of State Spaces III. Toy-Models. (arXiv:1411.3591v1 [gr-qc])

on 2014-11-14 9:23am GMT

Authors: Suzanne LanéryThomas Thiemann

In this series of papers, we investigate the projective framework initiated by Jerzy Kijowski and Andrzej Oko{\l}\’ow, which describes the states of a quantum theory as projective families of density matrices. A strategy to implement the dynamics in this formalism was presented in our first paper, which we now test in two simple toy-models. The first one is a very basic linear model, meant as an illustration of the general procedure, and we will only discuss it at the classical level. In the second one, we reformulate the Schr\”odinger equation, treated as a classical field theory, within this projective framework, and proceed to its (non-relativistic) second quantization. We are then able to reproduce the physical content of the usual Fock quantization.

Projective Limits of State Spaces I. Classical Formalism. (arXiv:1411.3589v1 [gr-qc])

on 2014-11-14 9:23am GMT

Authors: Suzanne LanéryThomas Thiemann

In this series of papers, we investigate the projective framework initiated by Jerzy Kijowski and Andrzej Oko{\l}\’ow, which describes the states of a quantum (field) theory as projective families of density matrices. The present first paper aims at clarifying the classical structures that underlies this formalism, namely projective limits of symplectic manifolds. In particular, this allows us to discuss accurately the issues hindering an easy implementation of the dynamics in this context, and to formulate a strategy for overcoming them.

Projective Limits of State Spaces II. Quantum Formalism. (arXiv:1411.3590v1 [gr-qc])

on 2014-11-14 9:23am GMT

Authors: Suzanne LanéryThomas Thiemann

In this series of papers, we investigate the projective framework initiated by Jerzy Kijowski and Andrzej Oko{\l}\’ow, which describes the states of a quantum theory as projective families of density matrices. After discussing the formalism at the classical level in a first paper, the present second paper is devoted to the quantum theory. In particular, we inspect in detail how such quantum projective state spaces relate to inductive limit Hilbert spaces and to infinite tensor product constructions. Regarding the quantization of classical projective structures into quantum ones, we extend the results by Oko{\l}\’ow [Oko{\l}\’ow 2013, arXiv:1304.6330], that were set up in the context of linear configuration spaces, to configuration spaces given by simply-connected Lie groups, and to holomorphic quantization of complex phase spaces.

Maximal correlation between flavor entanglement and oscillation damping due to localization effects. (arXiv:1411.3634v1 [hep-ph])

on 2014-11-14 9:22am GMT

Localization effects and quantum decoherence driven by the mass-eigenstate wave packet propagation are shown to support a statistical correlation between quantum entanglement and damped oscillations in the scenario of three-flavor quantum mixing for neutrinos. Once the mass-eigenstates that support flavor oscillations are identified as three-{\em qubit} modes, a decoherence scale can be extracted from correlation quantifiers, namely the entanglement of formation and the logarithmic negativity. Such a decoherence scale is compared with the coherence length of damped oscillations. Damping signatures exhibited by flavor transition probabilities as an effective averaging of the oscillating terms are then explained as owing to loss of entanglement between mass modes involved in the relativistic propagation.

Any additive Hamiltonian yields quantum theory. (arXiv:1411.3405v1 [quant-ph])

on 2014-11-14 9:22am GMT

Authors: Chris Fields

It is shown that no-signalling, a quantum of action, unitarity, detailed balance, Bell’s theorem, the Hilbert-space representation of physical states and the Born rule all follow from the assumption of an additive Hamiltonian together with Landauer’s principle. Common statements of the “classical limit” of quantum theory, as well as common assumptions made by “interpretations” of quantum theory, contradict additivity, Landauer’s principle, or both.

Less Interpretation and More Decoherence in Quantum Gravity and Inflationary Cosmology

Latest Results for Foundations of Physics

on 2014-11-14 12:00am GMT

Abstract

I argue that quantum decoherence—understood as a dynamical process entailed by the standard formalism alone—carries us beyond conceptual aspects of non-relativistic quantum mechanics deemed insurmountable by many contributors to the recent quantum gravity and cosmology literature. These aspects include various incarnations of the measurement problem and of the quantum-to-classical puzzle. Not only can such problems be largely bypassed or dissolved without default to a particular interpretation, but theoretical work in relativistic arenas stands to gain substantial physical and philosophical insight by incorporating decoherence phenomena.

General Non-Markovian Structure of Gaussian Master and Stochastic Schrödinger Equations

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

on 2014-11-12 3:00pm GMT

Author(s): L. Diósi and L. Ferialdi

General open quantum systems display memory features, their master equations are non-Markovian. We show that the subclass of Gaussian non-Markovian open system dynamics is tractable in a depth similar to the Markovian class. The structure of master equations exhibits a transparent generalization of …

[Phys. Rev. Lett. 113, 200403] Published Wed Nov 12, 2014

Modular localization and the holistic structure of causal quantum theory, a historical perspective. (arXiv:1107.1374v7 [math-ph] UPDATED)

on 2014-11-12 8:53am GMT

Authors: Bert Schroer

Recent insights into the conceptual structure of localization in QFT (“modular localization”) led to clarifications of old unsolved problems. The oldest one is the Einstein-Jordan conundrum which led Jordan in 1925 to the discovery of quantum field theory. This comparison of fluctuations in subsystems of heat bath systems (Einstein) with those resulting from the restriction of the QFT vacuum state to an open subvolume (Jordan) leads to a perfect analogy; the globally pure vacuum state becomes upon local restriction a strongly impure KMS state. This phenomenon of localization-caused thermal behavior as well as the vacuum-polarization clouds at the causal boundary of the localization region places localization in QFT into a sharp contrast with quantum mechanics and justifies the attribute “holstic”. In fact it positions the E-J Gedankenexperiment into the same conceptual category as the cosmological constant problem and the Unruh Gedankenexperiment. The holistic structure of QFT resulting from “modular localization” also leads to a revision of the conceptual origin of the crucial crossing property which entered particle theory at the time of the bootstrap S-matrix approach but suffered from incorrect use in the S-matrix settings of the dual model and string theory. The new holistic point of view, which strengthens the autonomous aspect of QFT, also comes with new messages for gauge theory by exposing the clash between Hilbert space structure and localization and presenting alternative solutions based on the use of stringlocal fields in Hilbert space. Among other things this leads to a radical reformulation of the Englert-Higgs symmetry breaking mechanism.

Conservation of information and the foundations of quantum mechanics. (arXiv:1411.2723v1 [quant-ph])

on 2014-11-12 8:53am GMT

Authors: G. ChiribellaC. M. Scandolo

We review a recent approach to the foundations of quantum mechanics inspired by quantum information theory. The approach is based on a general framework, which allows one to address a large class of physical theories which share basic information-theoretic features. We first illustrate two very primitive features, expressed by the axioms of causality and purity-preservation, which are satisfied by both classical and quantum theory. We then discuss the axiom of purification, which expresses a strong version of the Conservation of Information and captures the core of a vast number of protocols in quantum information. Purification is a highly non-classical feature and leads directly to the emergence of entanglement at the purely conceptual level, without any reference to the superposition principle. Supplemented by a few additional requirements, satisfied by classical and quantum theory, it provides a complete axiomatic characterization of quantum theory for finite dimensional systems.

Information Causality in the Quantum and Post-Quantum Regime. (arXiv:1406.5034v2 [quant-ph] UPDATED)

on 2014-11-12 8:52am GMT

Quantum correlations can be stronger than anything achieved by classical systems, yet they are not reaching the limit imposed by relativity. The principle of information causality offers a possible explanation for why the world is quantum and why there appear to be no even stronger correlations. Generalizing the no-signaling condition it suggests that the amount of accessible information must not be larger than the amount of transmitted information. Here we study this principle experimentally in the classical, quantum and post-quantum regimes. We simulate correlations that are stronger than allowed by quantum mechanics by exploiting the effect of polarization-dependent loss in a photonic Bell-test experiment. Our method also applies to other fundamental principles and our results highlight the special importance of anisotropic regions of the no-signalling polytope in the study of fundamental principles.

How to test the gauge-invariant non-local quantum dynamics of the Aharonov-Bohm effect. (arXiv:1411.2814v1 [quant-ph])

on 2014-11-12 8:52am GMT

Authors: T. Kaufherr

The gauge invariant non local quantum dynamics of the Aharonov-Bohm effect can be tested experimentally by measuring the instantaneous shift of the velocity distribution occurring when the particle passes by the flux line. It is shown that in relativistic quantum theory it is possible to measure the instantaneous velocity with accuracy sufficient to detect the change of the velocity distribution. In non relativistic quantum theory the instantaneous velocity can be measured to any desired accuracy.

Lorentzian Quantum Reality: Postulates and Toy Models. (arXiv:1411.2957v1 [quant-ph])

on 2014-11-12 8:52am GMT

We describe postulates for a novel realist version of relativistic quantum theory or quantum field theory in Minkowski space or other background spacetimes with suitable asymptotic properties. We illustrate their application in toy models.

Five measurement bases determine pure quantum states on any dimension. (arXiv:1411.2789v1 [quant-ph])

on 2014-11-12 8:52am GMT

A long standing problem in quantum mechanics is the minimum number of projective measurements required for the characterisation of unknown pure quantum states. The solution to this problem will be crucial for the developing field of high-dimensional quantum information processing. In this work we demonstrate that any pure state is unambiguously reconstructed by projective measurements onto five orthonormal bases for any d-dimensional Hilbert space. Thus, in our method the number of measurements (5d) scales linearly with d. The reconstruction is robust against experimental errors and requires simple post-processing, regardless of d. We experimentally demonstrate the feasibility of our scheme through the reconstruction of 8-dimensional quantum states, encoded in the transverse momentum of single photons, obtaining fidelities greater than 0.96 +/- 0.03.

Quantum Control by Imaging : The Zeno effect in an ultracold lattice gas. (arXiv:1411.2678v1 [cond-mat.quant-gas])

on 2014-11-12 8:52am GMT

Authors: Y. S. PatilS. ChakramM. Vengalattore

We demonstrate the control of quantum tunneling in an ultracold lattice gas by the measurement backaction imposed by an imaging process. A {\em in situ} imaging technique is used to acquire repeated images of an ultracold gas confined in a shallow optical lattice. The backaction induced by these position measurements modifies the coherent quantum tunneling of atoms within the lattice. By smoothly varying the rate at which spatial information is extracted from the atomic ensemble, we observe the continuous crossover from the ‘weak measurement regime’ where position measurements have little influence on the tunneling dynamics, to the ‘strong measurement regime’ where measurement-induced localization causes a large suppression of tunneling. This suppression of coherent tunneling is a manifestation of the Quantum Zeno effect. Our study realizes an experimental demonstration of the paradigmatic Heisenberg microscope in a lattice gas and sheds light on the implications of quantum measurement on the coherent evolution of a mesoscopic quantum system. In addition, this demonstrates a powerful technique for the control of an interacting many-body quantum system via spatially resolved measurement backaction.

Observation of topological transitions in interacting quantum circuits

Nature Latest Research

on 2014-11-12 12:00am GMT

Topology, with its abstract mathematical constructs, often manifests itself in physics and has a pivotal role in our understanding of natural phenomena. Notably, the discovery of topological phases in condensed-matter systems has changed the modern conception of phases of matter. The global nature of topological ordering, however, makes direct experimental probing an outstanding challenge. Present experimental tools are mainly indirect and, as a result, are inadequate for studying the topology of physical systems at a fundamental level. Here we employ the exquisite control afforded by state-of-the-art superconducting quantum circuits to investigate topological properties of various quantum systems. The essence of our approach is to infer geometric curvature by measuring the deflection of quantum trajectories in the curved space of the Hamiltonian. Topological properties are then revealed by integrating the curvature over closed surfaces, a quantum analogue of the Gauss–Bonnet theorem. We benchmark our technique by investigating basic topological concepts of the historically important Haldane model after mapping the momentum space of this condensed-matter model to the parameter space of a single-qubit Hamiltonian. In addition to constructing the topological phase diagram, we are able to visualize the microscopic spin texture of the associated states and their evolution across a topological phase transition. Going beyond non-interacting systems, we demonstrate the power of our method by studying topology in an interacting quantum system. This required a new qubit architecture that allows for simultaneous control over every term in a two-qubit Hamiltonian. By exploring the parameter space of this Hamiltonian, we discover the emergence of an interaction-induced topological phase. Our work establishes a powerful, generalizable experimental platform to study topological phenomena in quantum systems.

Nature 515 241 doi: 10.1038/nature13891

Observation of topological transitions in interacting quantum circuits

Nature – Issue – nature.com science feeds

on 2014-11-12 12:00am GMT

Observation of topological transitions in interacting quantum circuits

Nature 515, 7526 (2014). doi:10.1038/nature13891

Authors: P. Roushan, C. Neill, Yu Chen, M. Kolodrubetz, C. Quintana, N. Leung, M. Fang, R. Barends, B. Campbell, Z. Chen, B. Chiaro, A. Dunsworth, E. Jeffrey, J. Kelly, A. Megrant, J. Mutus, P. J. J. O’Malley, D. Sank, A. Vainsencher, J. Wenner, T. White, A. Polkovnikov, A. N. Cleland & J. M. Martinis

Topology, with its abstract mathematical constructs, often manifests itself in physics and has a pivotal role in our understanding of natural phenomena. Notably, the discovery of topological phases in condensed-matter systems has changed the modern conception of phases of matter. The global nature of topological ordering, however, makes direct experimental probing an outstanding challenge. Present experimental tools are mainly indirect and, as a result, are inadequate for studying the topology of physical systems at a fundamental level. Here we employ the exquisite control afforded by state-of-the-art superconducting quantum circuits to investigate topological properties of various quantum systems. The essence of our approach is to infer geometric curvature by measuring the deflection of quantum trajectories in the curved space of the Hamiltonian. Topological properties are then revealed by integrating the curvature over closed surfaces, a quantum analogue of the Gauss–Bonnet theorem. We benchmark our technique by investigating basic topological concepts of the historically important Haldane model after mapping the momentum space of this condensed-matter model to the parameter space of a single-qubit Hamiltonian. In addition to constructing the topological phase diagram, we are able to visualize the microscopic spin texture of the associated states and their evolution across a topological phase transition. Going beyond non-interacting systems, we demonstrate the power of our method by studying topology in an interacting quantum system. This required a new qubit architecture that allows for simultaneous control over every term in a two-qubit Hamiltonian. By exploring the parameter space of this Hamiltonian, we discover the emergence of an interaction-induced topological phase. Our work establishes a powerful, generalizable experimental platform to study topological phenomena in quantum systems.

Time evolution as refining, coarse graining and entangling. (arXiv:1311.7565v3 [gr-qc] UPDATED)

on 2014-11-11 11:38am GMT

Authors: Bianca DittrichSebastian Steinhaus

We argue that refining, coarse graining and entangling operators can be obtained from time evolution operators. This applies in particular to geometric theories, such as spin foams. We point out that this provides a construction principle for the physical vacuum in quantum gravity theories and more generally allows to construct a (cylindrically) consistent continuum limit of the theory.

A novel quantum-mechanical interpretation of the Dirac equation. (arXiv:1411.2296v1 [math-ph])

on 2014-11-11 11:38am GMT

A novel interpretation is given of Dirac’s “wave equation for the relativistic electron” as a quantum-mechanical one-particle equation. In this interpretation the electron and the positron are merely the two different “topological spin” states of a single more fundamental particle, not distinct particles in their own right. The new interpretation is backed up by the existence of such curious binary particle structures in general relativity, in particular the spacetime singularity of the maximal analytically extended, topologically non-trivial, electromagnetic Kerr–Newman spacetime in the zero-gravity limit (here, “zero-gravity” means the limit $G\to 0$, where $G$ is Newton’s constant of universal gravitation). This novel interpretation resolves the dilemma that Dirac’s wave equation seems to be capable of describing both the electron and the positron in “external” fields in many relevant situations (certainly not in all!), while the bi-spinorial wave function has only a single position variable in its argument, not two — as it should if it were a two-particle equation! The pertinent general-relativistic zero-gravity Hydrogen problem is studied in the usual Born–Oppenheimer approximation. Its spectral results suggest that the zero-$G$ Kerr–Newman magnetic moment be identified with the so-called “anomalous magnetic moment of the physical electron,” not with the Bohr magneton, so that the ring radius is only a tiny fraction of the electron’s Compton wave length.

The Emergence of Spacetime: Transactions and Causal Sets. (arXiv:1411.2072v1 [quant-ph])

on 2014-11-11 11:38am GMT

Authors: R. E. Kastner

This paper discusses how the transactional interpretation of quantum mechanics can provide for a natural account of the emergence of spacetime events from a quantum substratum. In this account, spacetime is not a substantive manifold that becomes occupied with events; rather, spacetime itself exists only in virtue of specific actualized events. This implies that spacetime is discrete rather than continuous, and that properties attributed to spacetime based on the notion of a continuum are idealizations that do not apply to the real physical world. It is further noted that the transactional picture of the emergence of spacetime can provide the quantum dynamics that underlie the causal set approach as proposed by Sorkin and others.

Quantum Oblivion: A Master Key for Many Quantum Riddles. (arXiv:1411.2278v1 [quant-ph])

on 2014-11-11 11:38am GMT

Authors: Avshalom C. ElitzurEliahu Cohen

A simple quantum interaction is analyzed, where the paths of two superposed particles asymmetrically cross, while a detector set to detect an interaction between them remains silent. Despite this negative result, the particles’ states leave no doubt that a peculiar interaction has occurred: One particle’s momentum changes while the other’s remains unaffected, in apparent violation of momentum conservation. Revisiting the foundations of the quantum measurement process offers the resolution. Prior to the macroscopic recording of no interaction, a brief Critical Interval prevails, during which the particles and the detector’s pointer form a subtle entanglement which immediately dissolves. It is this self-cancellation, henceforth “Quantum Oblivion (QO),” that lies at the basis of some well-known intriguing quantum effects. Such is Interaction-Free Measurement (IFM) [1] and its more paradoxical variants, like Hardy’s Paradox [2] and the Quantum Liar Paradox [3]. Even the Aharonov-Bohm (AB) effect [4] and weak measurement [5] turn out to belong to this group. We next study interventions within the Critical Interval that produce some other peculiar effects. Finally we discuss some of the conceptual issues involved. Under the time-resolution of the Critical Interval, some nonlocal phenomena turn out to be local. Momentum is conserved due to the quantum uncertainties inflicted by the particle-pointer interaction, which sets the experiment’s final boundary condition.

Influence of the measurement on the decay law: the bang-bang case. (arXiv:1411.2255v1 [quant-ph])

on 2014-11-11 11:38am GMT

Authors: Francesco GiacosaGiuseppe Pagliara

After reviewing the description of an unstable state in the framework of nonrelativistic Quantum Mechanics (QM) and relativistic Quantum Field Theory (QFT), we consider the effect of pulsed, ideal measurements repeated at equal time intervals on the lifetime of an unstable system. In particular, we investigate the case in which the `bare’ survival probability is an exact exponential (a very good approximation in both QM and QFT), but the measurement apparatus can detect the decay products only in a certain energy range. We show that the Quantum Zeno Effect can occur in this framework as well.

A quantum arrow of time. (arXiv:1411.2178v1 [quant-ph])

on 2014-11-11 11:38am GMT

Authors: Alberto C. de la Torre

It is shown that position-momentum correlation is never decreasing and therefore it is a good candidate as a quantum arrow of time devoid of shortcomings of other proposals.

Quantum Mechanics and Perceptive Processes: a reply to Elio Conte. (arXiv:1411.2159v1 [quant-ph])

on 2014-11-11 11:38am GMT

Authors: GianCarlo Ghirardi

Recently, Elio Conte has commented a paper by the present author devoted to analyze the possibility of checking experimentally whether the perceptual process can lead to the collapse of the wavefunction. Here we answer to the comments by Conte and we show that he has missed to grasp the crucial elements of our proposal. Morever, we discuss some ideas put forward by Conte concerning the occurrence of quantum superpositions of different states of consciousness and we show that they are rather vague and not cogent.

First-Person Plural Quantum Mechanics

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

on 2014-11-10 9:30pm GMT

Mohrhoff, Ulrich J. (2014) First-Person Plural Quantum Mechanics. [Preprint]

show enclosure

Increase of entanglement by local PT-symmetric operations

PRA: Quantum information

on 2014-11-10 3:00pm GMT

Author(s): Shin-Liang Chen, Guang-Yin Chen, and Yueh-Nan Chen

Entanglement plays a central role in the field of quantum information science. It is well known that the degree of entanglement cannot be increased under local operations. Here, we show that the concurrence of a bipartite entangled state can be increased under the local PT-symmetric operation. This …

[Phys. Rev. A 90, 054301] Published Mon Nov 10, 2014

State disturbance and pointer shift in protective quantum measurements

PRA: Fundamental concepts

on 2014-11-10 3:00pm GMT

Author(s): Maximilian Schlosshauer

We investigate the disturbance of the state of a quantum system in a protective measurement for finite measurement times and different choices of the time-dependent system-apparatus coupling function. The ability to minimize this state disturbance is essential to protective measurement. We show that…

[Phys. Rev. A 90, 052106] Published Mon Nov 10, 2014

Absence of Unruh effect in polymer quantization. (arXiv:1411.1935v1 [gr-qc])

on 2014-11-10 12:05pm GMT

Authors: Golam Mortuza HossainGopal Sardar

Unruh effect is a landmark prediction of standard quantum field theory in which Fock vacuum state appears as a thermal state with respect to an uniformly accelerating observer. Given its dependence on trans-Planckian modes, Unruh effect is often considered as an arena for exploring a candidate theory of quantum gravity. Here we show that Unruh effect disappears if, instead of using Fock quantization, one uses polymer quantization or loop quantization, the quantization method used in loop quantum gravity. Secondly, the polymer vacuum state remains a vacuum state even for the accelerating observer in the sense that expectation value of number density operator in it remains zero. Finally, if experimental measurement of Unruh effect is ever possible then it may be used either to verify or rule out a theory of quantum gravity.

The Copenhagen Interpretation Born Again. (arXiv:1411.2025v1 [quant-ph])

on 2014-11-10 12:05pm GMT

Authors: Timothy J. Hollowood

An approach to quantum mechanics is developed which makes the Heisenberg cut between the deterministic microscopic quantum world and the partly deterministic, partly stochastic macroscopic world explicit. The microscopic system evolves according to the Schrodinger equation with stochastic behaviour arising when the system is probed by a set of coarse grained macroscopic observables whose resolution scale defines the Heisenberg cut. The resulting stochastic process can account for the different facets of the classical limit: Newton’s laws (ergodicity broken); statistical mechanics of thermal ensembles (ergodic); and solve the measurement problem (partial ergodicity breaking). In particular, the usual rules of the Copenhagen interpretation, like the Born rule, emerge, along with completely local descriptions of EPR type experiments. The formalism also re-introduces a dynamical picture of equilibration and thermalization in quantum statistical mechanics and provides insight into how classical statistical mechanics can arise in the classical limit and in a way that alleviates various conceptual problems.

CHSH Inequality: Quantum Probabilities as Classical Conditional Probabilities

Latest Results for Foundations of Physics

on 2014-11-09 12:00am GMT

Abstract

In this note we demonstrate that the results of observations in the EPR–Bohm–Bell experiment can be described within the classical probabilistic framework. However, the “quantum probabilities” have to be interpreted as conditional probabilities, where conditioning is with respect to fixed experimental settings. Our approach is based on the complete account of randomness involved in the experiment. The crucial point is that randomness of selections of experimental settings has to be taken into account within one consistent framework covering all events related to the experiment. This approach can be applied to any complex experiment in which statistical data are collected for various (in general incompatible) experimental settings.