Special Issue "New Trends in Quantum Electrodynamics"

A special issue of Symmetry (ISSN 2073-8994). This special issue belongs to the section "Physics and Symmetry/Asymmetry".

Deadline for manuscript submissions: closed (15 July 2018).

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A printed edition of this Special Issue is available here.

Special Issue Editor

Prof. Dr. Roberto Passante
E-Mail Website
Guest Editor
1. Dipartimento di Fisica e Chimica, Universita' degli Studi di Palermo, Via Archirafi 36, I-90123 Palermo, Italy
2. INFN, Laboratori Nazionali del Sud, Via S. Sofia 44, I-95123 Catania, Italy
Interests: casimir physics; quantum electrodynamics; quantum fluctuations; radiative processes in static and dynamical structured environments; quantum field theory in accelerated frames and in a curved space-time; PT symmetric non-Hermitian Hamiltonians in quantum mechanics; quantum optomechanics; resonances and dressed unstable states; microscopic origin of time asymmetry in quantum physics; cosmological axions and dark matter
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Special Issue Information

Dear Colleagues,

Quantum Electrodynamics is one of the most successful physical theories, in which predictions agree with experimental results with exceptional accuracy. Nowadays, even after several decades since its introduction, it is a very active research field from both theoretical and experimental point of view. The aim of this Special Issue is to present recent relevant advances in quantum electrodynamics, both theoretical and experimental, and related aspects in quantum field theory and quantum optics.

Topics that will be included are:

  • Quantum electrodynamics in external environments such as static or moving boundaries
  • Cavity quantum electrodynamics
  • Coherent energy transfer
  • Macroscopic quantum electrodynamics
  • Radiative processes in structured environments such as static and dynamic photonic crystals or photonic crystals waveguides
  • Physical phenomena related to vacuum fluctuations, including cosmological aspects
  • Dispersion and resonance interactions between atoms
  • Casimir and Casimir-Polder effects, also in nonequilibrium configurations
  • Quantum optomechanics
  • Quantum electrodynamics in curved space and the Unruh effect
Prof. Roberto Passante
Guest Editor

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Symmetry is an international peer-reviewed open access monthly journal published by MDPI.

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Keywords

  • Quantum electrodynamics
  • Cavity quantum electrodynamics
  • Macroscopic quantum electrodynamics
  • Vacuum fluctuations
  • Quantum electrodynamics in external backgrounds
  • Unruh effect
  • Quantum optomechanics
  • Photonic crystals

Published Papers (6 papers)

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Research

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Article
Three-Body Dispersion Potentials Involving Electric Octupole Coupling
Symmetry 2018, 10(8), 343; https://0-doi-org.brum.beds.ac.uk/10.3390/sym10080343 - 16 Aug 2018
Cited by 1 | Viewed by 1510
Abstract
Non-pairwise additive three-body dispersion potentials dependent upon one or more electric octupole moments are evaluated using the theory of molecular quantum electrodynamics. To simplify the perturbation theory calculations, an effective two-photon interaction Hamiltonian operator is employed. This leads to only third-order theory being [...] Read more.
Non-pairwise additive three-body dispersion potentials dependent upon one or more electric octupole moments are evaluated using the theory of molecular quantum electrodynamics. To simplify the perturbation theory calculations, an effective two-photon interaction Hamiltonian operator is employed. This leads to only third-order theory being required to evaluate energy shifts instead of the usual sixth-order formula, and the summation over six time-ordered sequences of virtual photon creation and annihilation events. Specific energy shifts computed include DD-DD-DO, DD-DO-DO, DO-DO-DO, and DD-DO-OO terms, where D and O are electric dipole and octupole moments, respectively. The formulae obtained are applicable to an arbitrary arrangement of the three particles, and we present explicit results for the equilateral triangle and collinear configurations, which complements the recently published DD-DD-OO potential. In this last case it was found that the contribution from the octupole weight-1 term could be viewed as a higher-order correction to the triple-dipole dispersion potential DD-DD-DD. In a similar fashion the octupole moment is decomposed into its irreducible components of weights-1 and -3, enabling insight to be gained into the potentials obtained in this study. Dispersion interaction energies proportional to mixed dipole-octupole polarisabilities, for example, are found to depend only on the weight-1 octupole moment for isotropic species and are retarded. Additional approximations are necessary in the evaluation of wave vector integrals for these cases in order to yield energy shifts that are valid in the near-zone. Full article
(This article belongs to the Special Issue New Trends in Quantum Electrodynamics)
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Article
Ultrafast Dynamics of High-Harmonic Generation in Terms of Complex Floquet Spectral Analysis
Symmetry 2018, 10(8), 313; https://0-doi-org.brum.beds.ac.uk/10.3390/sym10080313 - 01 Aug 2018
Cited by 6 | Viewed by 1512
Abstract
We studied the high-harmonic generation (HHG) of a two-level-system (TLS) driven by an intense monochromatic phase-locked laser based on complex spectral analysis with the Floquet method. In contrast with phenomenological approaches, this analysis deals with the whole process as a coherent quantum process [...] Read more.
We studied the high-harmonic generation (HHG) of a two-level-system (TLS) driven by an intense monochromatic phase-locked laser based on complex spectral analysis with the Floquet method. In contrast with phenomenological approaches, this analysis deals with the whole process as a coherent quantum process based on microscopic dynamics. We have obtained the time-frequency resolved spectrum of spontaneous HHG single-photon emission from an excited TLS driven by a laser field. Characteristic spectral features of the HHG, such as the plateau and cutoff, are reproduced by the present model. Because the emitted high-harmonic photon is represented as a superposition of different frequencies, the Fano profile appears in the long-time spectrum as a result of the quantum interference of the emitted photon. We reveal that the condition of the quantum interference depends on the initial phase of the driving laser field. We have also clarified that the change in spectral features from the short-time regime to the long-time regime is attributed to the interference between the interference from the Floquet resonance states and the dressed radiation field. Full article
(This article belongs to the Special Issue New Trends in Quantum Electrodynamics)
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Article
Resonance Dipole–Dipole Interaction between Two Accelerated Atoms in the Presence of a Reflecting Plane Boundary
Symmetry 2018, 10(6), 185; https://0-doi-org.brum.beds.ac.uk/10.3390/sym10060185 - 28 May 2018
Cited by 10 | Viewed by 1354
Abstract
We study the resonant dipole–dipole interaction energy between two non-inertial identical atoms, one excited and the other in the ground state, prepared in a correlated Bell-type state, and interacting with the scalar field or the electromagnetic field nearby a perfectly reflecting plate. We [...] Read more.
We study the resonant dipole–dipole interaction energy between two non-inertial identical atoms, one excited and the other in the ground state, prepared in a correlated Bell-type state, and interacting with the scalar field or the electromagnetic field nearby a perfectly reflecting plate. We suppose the two atoms move with the same uniform acceleration, parallel to the plane boundary, and that their separation is constant during the motion. By separating the contributions of radiation reaction field and vacuum fluctuations to the resonance energy shift of the two-atom system, we show that Unruh thermal fluctuations do not affect the resonance interaction, which is exclusively related to the radiation reaction field. However, non-thermal effects of acceleration in the radiation-reaction contribution, beyond the Unruh acceleration–temperature equivalence, affect the resonance interaction energy. By considering specific geometric configurations of the two-atom system relative to the plate, we show that the presence of the mirror significantly modifies the resonance interaction energy between the two accelerated atoms. In particular, we find that new and different features appear with respect to the case of atoms in the free-space, related to the presence of the boundary and to the peculiar structure of the quantum electromagnetic field vacuum in the locally inertial frame. Our results suggest the possibility to exploit the resonance interaction between accelerated atoms as a probe for detecting the elusive effects of atomic acceleration on radiative processes. Full article
(This article belongs to the Special Issue New Trends in Quantum Electrodynamics)
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Review

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Review
Dispersion Interactions between Neutral Atoms and the Quantum Electrodynamical Vacuum
Symmetry 2018, 10(12), 735; https://0-doi-org.brum.beds.ac.uk/10.3390/sym10120735 - 10 Dec 2018
Cited by 11 | Viewed by 1040
Abstract
Dispersion interactions are long-range interactions between neutral ground-state atoms or molecules, or polarizable bodies in general, due to their common interaction with the quantum electromagnetic field. They arise from the exchange of virtual photons between the atoms, and, in the case of three [...] Read more.
Dispersion interactions are long-range interactions between neutral ground-state atoms or molecules, or polarizable bodies in general, due to their common interaction with the quantum electromagnetic field. They arise from the exchange of virtual photons between the atoms, and, in the case of three or more atoms, are not additive. In this review, after having introduced the relevant coupling schemes and effective Hamiltonians, as well as properties of the vacuum fluctuations, we outline the main properties of dispersion interactions, both in the nonretarded (van der Waals) and retarded (Casimir–Polder) regime. We then discuss their deep relation with the existence of the vacuum fluctuations of the electromagnetic field and vacuum energy. We describe some transparent physical models of two- and three-body dispersion interactions, based on dressed vacuum field energy densities and spatial field correlations, which stress their deep connection with vacuum fluctuations and vacuum energy. These models give a clear insight of the physical origin of dispersion interactions, and also provide useful computational tools for their evaluation. We show that this aspect is particularly relevant in more complicated situations, for example when macroscopic boundaries are present. We also review recent results on dispersion interactions for atoms moving with noninertial motions and the strict relation with the Unruh effect, and on resonance interactions between entangled identical atoms in uniformly accelerated motion. Full article
(This article belongs to the Special Issue New Trends in Quantum Electrodynamics)
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Review
Quasi-Lie Brackets and the Breaking of Time-Translation Symmetry for Quantum Systems Embedded in Classical Baths
Symmetry 2018, 10(10), 518; https://0-doi-org.brum.beds.ac.uk/10.3390/sym10100518 - 16 Oct 2018
Cited by 10 | Viewed by 1415
Abstract
Many open quantum systems encountered in both natural and synthetic situations are embedded in classical-like baths. Often, the bath degrees of freedom may be represented in terms of canonically conjugate coordinates, but in some cases they may require a non-canonical or non-Hamiltonian representation. [...] Read more.
Many open quantum systems encountered in both natural and synthetic situations are embedded in classical-like baths. Often, the bath degrees of freedom may be represented in terms of canonically conjugate coordinates, but in some cases they may require a non-canonical or non-Hamiltonian representation. Herein, we review an approach to the dynamics and statistical mechanics of quantum subsystems embedded in either non-canonical or non-Hamiltonian classical-like baths which is based on operator-valued quasi-probability functions. These functions typically evolve through the action of quasi-Lie brackets and their associated Quantum-Classical Liouville Equations, or through quasi-Lie brackets augmented by dissipative terms. Quasi-Lie brackets possess the unique feature that, while conserving the energy (which the Noether theorem links to time-translation symmetry), they violate the time-translation symmetry of their algebra. This fact can be heuristically understood in terms of the dynamics of the open quantum subsystem. We then describe an example in which a quantum subsystem is embedded in a bath of classical spins, which are described by non-canonical coordinates. In this case, it has been shown that an off-diagonal open-bath geometric phase enters into the propagation of the quantum-classical dynamics. Next, we discuss how non-Hamiltonian dynamics may be employed to generate the constant-temperature evolution of phase space degrees of freedom coupled to the quantum subsystem. Constant-temperature dynamics may be generated by either a classical Langevin stochastic process or a Nosé–Hoover deterministic thermostat. These two approaches are not equivalent but have different advantages and drawbacks. In all cases, the calculation of the operator-valued quasi-probability function allows one to compute time-dependent statistical averages of observables. This may be accomplished in practice using a hybrid Molecular Dynamics/Monte Carlo algorithms, which we outline herein. Full article
(This article belongs to the Special Issue New Trends in Quantum Electrodynamics)
Review
Symmetries, Conserved Properties, Tensor Representations, and Irreducible Forms in Molecular Quantum Electrodynamics
Symmetry 2018, 10(7), 298; https://0-doi-org.brum.beds.ac.uk/10.3390/sym10070298 - 23 Jul 2018
Cited by 11 | Viewed by 1954
Abstract
In the wide realm of applications of quantum electrodynamics, a non-covariant formulation of theory is particularly well suited to describing the interactions of light with molecular matter. The robust framework upon which this formulation is built, fully accounting for the intrinsically quantum nature [...] Read more.
In the wide realm of applications of quantum electrodynamics, a non-covariant formulation of theory is particularly well suited to describing the interactions of light with molecular matter. The robust framework upon which this formulation is built, fully accounting for the intrinsically quantum nature of both light and the molecular states, enables powerful symmetry principles to be applied. With their origins in the fundamental transformation properties of the electromagnetic field, the application of these principles can readily resolve issues concerning the validity of mechanisms, as well as facilitate the identification of conditions for widely ranging forms of linear and nonlinear optics. Considerations of temporal, structural, and tensorial symmetry offer significant additional advantages in correctly registering chiral forms of interaction. More generally, the implementation of symmetry principles can considerably simplify analysis by reducing the number of independent quantities necessary to relate to experimental results to a minimum. In this account, a variety of such principles are drawn out with reference to applications, including recent advances. Connections are established with parity, duality, angular momentum, continuity equations, conservation laws, chirality, and spectroscopic selection rules. Particular attention is paid to the optical interactions of molecules as they are commonly studied, in fluids and randomly organised media. Full article
(This article belongs to the Special Issue New Trends in Quantum Electrodynamics)
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