Self-dressing in classical and quantum electrodynamics

A short review is presented of the theory of dressed states in nonrelativistic QED, encompassing fully and partially dressed states in atomic physics. This leads to the concept of the reconstruction of the cloud of virtual photons and of self-dressing. Finally some recent results on the classical counterpart of self-dressing are discussed and a comparison is made with the QED case. Attention is drawn to open problems and future lines of research are briefly outlined.

Nonlocal field correlations and dynamical Casimir-Polder forces between one excited- and two ground-state atoms

The problem of nonlocality in the dynamical three-body Casimir-Polder interaction between an initially excited and two ground-state atoms is considered. It is shown that the nonlocal spatial correlations of the field emitted by the excited atom during the initial part of its spontaneous decay may become manifest in the three-body interaction. The observability of this new phenomenon is discussed.

Exact Canonical Dressing of Two-Level Atoms by Two-Photon Processes

The aim of this paper is to present new exact results on the subject of dressing of a two-level atom by an electromagnetic field.

Quantum beats from dressed three-level atoms

Abstract By extending a previously developed unitary transformation technique to dress three-level atoms by a strong driving radiation field, we show that quantum beats can be induced by the presence of the driving field also when the decay channels lead from a singlet to a doublet of lower energy. A qualitative explanation of this effect is presented, which is based on the quantum theory of measurement.

The dynamics of the electron in a homonuclear driven molecular ion

Abstract The radiation diffused by a one-dimensional homonuclear molecular ion driven by a laser field is studied as a function of the time. When the photon energy is resonant with the energy gap between the ground and the first excited state, the electronic probability density is seen to undergo slow and deep oscillations between the two nuclei. Synchronous to such oscillations, deep modulations of the emitted power are observed. The period of oscillation is of the order of 10 optical cycles. Detection of the variation in the intensity of the emitted electromagnetic spectrum therefore brings information on the position of the electron in the molecule.

Interaction between strong radiation fields and two-level atoms: A canonical transformation approach

The Study Of The Nuclear Motion In D2+ Molecular Ion By Using The Harmonic Spectra

In this paper we show how it is possible to investigate the nuclei dynamics of a D2+ molecular ion by using the high harmonic generation spectra emitted by the system when subjected to an intense laser field. In particular, the emitted spectra contains, in addition to the usual odd harmonic peaks, additional satellite peaks whose frequency spacing is equal to the vibrational frequency of the nuclei.

Causality, non-locality and three-body Casimir–Polder energy between three ground-state atoms

The problem of relativistic causality in the time-dependent three-body Casimir–Polder interaction energy between three atoms, initially in their bare ground-state, is discussed. It is shown that the non-locality of the spatial correlations of the electromagnetic field emitted by the atoms during their dynamical self-dressing may become manifest in the dynamical three-body Casimir–Polder interaction energy between the three atoms.

Edwin Power and the birth of dressed atoms

This paper reviews the main results of a twenty year-long international collaborative effort led by the late E.A. Power on the physics of atoms dressed by the vacuum electromagnetic field. The presentation uses the historical, rather than the logical, order of development. This permits one to shed light on the influence of Power's personality and human qualities on the birth and evolution of the notion of the dressed atom, which is central to modern non-relativistic QED.

Dynamical Casimir-Polder energy between an excited- and a ground-state atom.

We consider the Casimir-Polder interaction between two atoms, one in the ground state and the other in its excited state. The interaction is time-dependent for this system, because of the dynamical self-dressing and the spontaneous decay of the excited atom. We calculate the dynamical Casimir-Polder potential between the two atoms using an effective Hamiltonian approach. The results obtained and their physical meaning are discussed and compared with previous results based on a time-independent approach which uses a non-normalizable dressed state for the excited atom.

Nonlocal properties of dynamical three-body Casimir-Polder forces

We consider the three-body Casimir-Polder interaction between three atoms during their dynamical self-dressing. We show that the time-dependent three-body Casimir-Polder interaction energy displays nonlocal features related to quantum properties of the electromagnetic field and to the nonlocality of spatial field correlations. We discuss the measurability of this intriguing phenomenon and its relation with the usual concept of stationary three-body forces.

Quantum Disorder in Macroscopic Systems of Interacting Atoms and Radiation Fields

The linear interaction between a system of two-level atoms and an electromagnetic field can be described as taking place through a number of elementary acts in which photons are absorbed or emitted, while atoms change their states. It is conceivable that these processes tend to modify the original statistical properties characteristic of the atomic system and of the electromagnetic field at t = 0, when we assume that the interaction is “turned on”. The problem is of conceptual importance, and might become of practical importance in connection with laser processes in unusual ranges of frequency. In fact, it has recently received increasing attention in the case of one-photon interactions [1]…

A three-colour scheme to generate isolated attosecond pulses

We propose a new scheme to produce isolated attosecond pulses, involving the use of three laser pulses: a fundamental laser field of intensity I = 3.5 × 1014 W cm−2 and of wavelength λ = 820 nm, and two properly chosen weak lasers with wavelengths 1.5λ and 0.5λ. The three lasers have a Gaussian envelope of 36 fs full width at half maximum. The resulting total field is an asymmetric electric field with an isolated peak. We show that a model atom, interacting with the above-defined total field, generates an isolated attosecond pulse as short as 1/10 of a laser period, i.e. approximately 270 as.

Pulse-duration dependence of the isotopic effect in simple molecular ions driven by strong laser fields

In this paper we discuss isotopic effects in simple molecular ions subjected to strong laser fields. We show that the intensity of the emitted spectra strongly depends upon both the nuclear mass of the molecular ions and the laser pulse duration. In particular, for short pulse duration [up to 8 optical cycles (o.c.)], we confirm the trend described in the most studied case in which the high-order harmonic generation is more efficient for heavier isotopes; in contrast, an interesting physical phenomenon is predicted for pulses longer than 16 o.c. characterized by an inverse effect in which lighter molecular species are responsible for higher-order harmonic emission.

Vacuum field correlations and three-body Casimir-Polder potential with one excited atom

The three-body Casimir-Polder potential between one excited and two ground-state atoms is evaluated. A physical model based on the dressed field correlations of vacuum fluctuations is used, generalizing a model previously introduced for three ground-state atoms. Although the three-body potential with one excited atom is already known in the literature, our model gives new insights on the nature of non-additive Casimir-Polder forces with one or more excited atoms.

Spatial correlations of vacuum fluctuations and the Casimir-Polder potential

We calculate the Casimir-Polder intermolecular potential using an effective Hamiltonian recently introduced. We show that the potential can be expressed in terms of the dynamical polarizabilities of the two atoms and the equal-time spatial correlation of the electric field in the vacuum state. This gives support to an interesting physical model recently proposed in the literature, where the potential is obtained from the classical interaction between the instantaneous atomic dipoles induced and correlated by the vacuum fluctuations. Also, the results obtained suggest a more general validity of this intuitive model, for example when external boundaries or thermal fields are present.

The limits of the rotating wave approximation in electromagnetic field propagation in a cavity

We consider three two-level atoms inside a one-dimensional cavity, interacting with the electromagnetic field in the rotating wave approximation (RWA), commonly used in the atom-radiation interaction. One of the three atoms is initially excited, and the other two are in their ground state. We numerically calculate the propagation of the field spontaneously emitted by the excited atom and scattered by the second atom, as well as the excitation probability of the second and third atom. The results obtained are analyzed from the point of view of relativistic causality in the atom-field interaction. We show that, when the RWA is used, relativistic causality is obtained only if the integrations …

Squeezing in a two-photon Dicke hamiltonian

Abstract The single-mode, two-level atom Dicke hamiltonian with two-photon atom-field coupling is treated exactly and it is shown to yield a certain degree of squeezing in the field variables. This result is briefly discussed in connection with the previously shown absence of squeezing in the two-photon laser model.

Second harmonic generation by an isolated spin

Abstract The second harmonic generation at microwave frequency by a spin S = 1 2 in a cavity has been studied as a function of the external magnetic field using a resolvent technique, and the average transition rates to states with an increased number of double-frequency photons has been calculated. In spite of the crudeness of the model, a good qualitative agreement has been found between the predictions of the present theory and recent experimental results on non-linear behaviour of paramagnetic spin systems in a microwave field.

Time-dependent Casimir-Polder forces and partially dressed states

A time-dependent Casimir–Polder force is shown to arise during the time evolution of a partially dressed two-level atom. The partially dressed atom is obtained by a rapid change of an atomic parameter such as its transition frequency, due to the action of some external agent. The electromagnetic field fluctuations around the atom, averaged over the solid angle for simplicity, are calculated as a function of time, and it is shown that the interaction energy with a second atom yields a dynamical Casimir–Polder potential between the two atoms.

Excitation Spectrum of a Linear Chain of Paramagnetic Atoms with Spin-Phonon Interaction

The low-lying energy levels of a paramagnetic chain in the presence of spin-phonon interaction have been investigated. It is shown that there is no gap in the one-particle excitation spectrum.

Theory of the dynamical behaviour of inverted spins linearly coupled to a lattice

Abstract The relaxation process of a system of paramagnetic spins linearly interacting with a phonon field is studied in the region of inverted population of the levels. The peculiar dynamical behaviour of the present model in that region is shown to be in agreement with some recent experimental results.

Generation of isolated attosecond pulses using unipolar and laser fields

A new scheme to generate isolated attosecond pulses is presented that involves the use of a laser field and of a unipolar field. The laser field has a pulse of intensity I = 1.5×1014 W cm−2 and wavelength λ = 820 nm. The unipolar pulse is an asymmetric pulse consisting of a sharp peak, lasting approximately half a laser period, i.e. nearly 1.4 fs, followed by a long and shallow tail. We show that on combining these two fields, it is possible to generate isolated attosecond pulses as short as 1/10 of a laser period, i.e. approximately 270 as. Moreover, it is argued that this scheme is robust either against small variations of the laser envelope, or against small changes in the delay between …

Phonon Bandwidth and Rate Equations in Avalanche Relaxation