Collective Classical and Quantum Fields

R. A. Ismailov, Alexander Ya. Kazakov

N three-level atoms interact simultaneously with classical and quantum fields, which are in quasiresonance with various atomic transitions. The classical and quantum fields exchange photons by means of the atoms. It is shown that under certain conditions this process is collective. The number of photons in a quantized mode oscillates, and the amplitude of these oscillations is proportional to N 2. The frequency of the oscillations is determined by the frequencies of the classical and external fields.

Hagen M. Kleinert

R. Bonifacio, Mary M. Cola, N. Piovella +1 more

Free Electron Laser (FEL) and Collective Atomic Recoil Laser (CARL) are described by the same model of classical equations for properly defined scaled variables. These equations are extended to the quantum domain describing the particle's motion by a Schrödinger equation coupled to a self-consistent radiation field. The model depends on a single collective parameter which represents the maximum number of photons emitted per particle. We demonstrate that the classical model is recovered in the limit >> 1, in which the Wigner function associated to the Schrödinger equation obeys to the classical Vlasov equation. On the contrary, for ⩽ 1, a new quantum regime is obtained in which both FELs and CARLs behave as a two-state system coupled to the self-consistent radiation field and described by Maxwell-Bloch equations.

Massoud Akbari-Moghanjoughi

Abstract In current research we investigate macroscopic collective quantum effects in interacting electron gas with arbitrary degree of degeneracy due to electrostatic field-density coupling. It is found that in the one dimensional excitation model deterministic quantum charge transport can take place due to the electrostatic field coupling of the interacting electron correlations with number density variations of the electron gas. A new expression for probability current is found to be valid for collective excitations in interacting electron gas. It is also revealed that the phase-space evolution of modified Wigner distribution function for linear quasiparticle excitations resembles that of the classical free particle. In other words, semiclassical linear evolution of collective excitations in interacting quantum electron gas is quite analogous to dynamics of classical system of particles in the absence of external forces, where the interparticle electrostatic forces play the analogous role of internal classical forces. It is shown that the electrostatic field of electrons when coupled to collective electron wavefunction can also lead to directly measurable macroscopic phenomena. It is remarked that the interacting system of electrons simultaneously exhibits microscopic and macroscopic effects that are linked through the dual lengthscale behavior of collective quantum electron excitations.