Coherent dynamics of radiating atomic systems in pseudospin representation

Abstract

The aim of this review is twofold. First, a general approach is presented allowing for a unified description of dynamics in radiating systems of different nature. Both atomic systems as well as spin assemblies can be treated in the frame of the same mathematical method based on pseudospin (or spin) representation of evolution equations. The approach is applicable to all stages of radiation dynamics, including the most difficult initial quantum stage, where coherence is not yet developed. This makes it possible to study the process of coherent self-organization from the chaotic quantum stage. Second, the approach is illustrated by applying it for the description of several coherent phenomena. Different types of superradiance are characterized: pure superradiance, triggered superradiance, pulsing and punctuated superradiance. The theory is presented of such interesting effects as triggering dipolar waves, turbulent photon filamentation, collective liberation of light, pseudospin atomic squeezing, and operator entanglement production.

Superradiance by ferroelectrics in cavity resonators

“…But here, the resonator not merely enhances the coherent radiation, but induces coherence as such. Although mathematically there are direct analogies between spontaneous radiation of atoms and dipole waves and between the common radiation field of atoms and the resonator feedback field [65,71], but anyway the physics of atomic superradiance and ferroelectric superradiance is rather different.…”

Spin superradiance by magnetic nanomolecules and nanoclusters

“…The maximal number of coherently radiating spins can be estimated as N coh ∼ ρV coh , where ρ is the density of nanomolecules and V coh is the coherence volume. The latter, for a cylindrical sample, is V coh ∼ πR 2 coh L, where L is the cylinder length and R coh is a coherence radius [39], which is of order 0.3 √ λL. This gives…”

“…If the wavelength is larger than the sample linear size, then ϕ 0 ≃ 1. But, when the wavelength is shorter than the system linear size, then the form-factor essentially depends on the sample shape [39,40]. We have accomplished computer simulation for N magnetic nanomolecules possessing spin S = 10, such as Mn 12 or Fe 8 , employing the parameters typical of these nanomolecules, for which D 2 and D 4 are negligible.…”

Order Indices and Entanglement Production in Quantum Systems

“…Therefore the temporal behavior of these coherent phenomena can also be accompanied by drastic changes in the order indices and entanglement production. Examples of these phenomena are given by the dynamics of strongly nonequilibrium spin systems [ 132 , 133 ] and radiating systems [ 134 , 135 , 136 ]. Being many-particle collections, these systems allow for considering order indices and entanglement production characterizing their temporal behavior.…”