We developed a semiclassical theory of polariton excitations for the Λ-scheme of interaction realized in an yttrium orthosilicate crystal doped with Pr 59 atoms. The threshold optical pump power for efficient amplification of the probefield polaritons in a medium consisting of three-level atoms is determined. At the near-threshold conditions in the system the appearance of strong non-classical correlations (entanglement) between light and dark polaritons, similar to generation of biphotons in optics is predicted.
The nonlinear theory of formation of entangled polaritons of probe field in the case of Raman interaction scheme in Y2SiO5 crystal doped by 59Pr atoms is developed. The model of polariton waveguide with doped medium inside based on Fabry-Prot interferometer is suggested. The opportunity of dynamic amplification of entangled polaritons in such a system is shown.
The interaction of a two-level atomic ensemble with a quantized single mode electromagnetic field in the presence of
optical collisions is theoretically investigated. The main accent is made on achieving thermal equilibrium for coupled
atom-light states (in particular dressed states). We propose a model of atomic dressed state thermalization that accounts
for the evolution of the pseudo-spin Bloch vector components and characterize the essential role of the spontaneous
emission rate in the thermalization process. Our model shows that the time of thermalization of the coupled atom-light
states strictly depends on the ratio of the detuning and the resonant Rabi frequency. The predicted time of thermalization
is in the nanosecond domain and about ten times shorter than the natural lifetime of rubidium D-lines.
A new developed for storing quantum information on atomic polaritons being at thermal equilibrium is developed
for the first time. We propose a new type of spatially periodic structure - polaritonic crystal (PolC) formed
by trapped two-level atoms interacting with quantum electromagnetic field in one-dimensional array of tunnelcoupled
microcavities, which allows polaritons to be fully localized. The quantum degeneracy and phase transition
to superfluid (Bardeen-Cooper-Schrieffer-type) state for low branch polaritons is discussed. The principal result is
that the group velocity of polaritons depends essentially on the order parameter of the system, i.e. on the average
photon number in the cavity array. An algorithm for the spatially distributed writing, storing, and retrieving of
quantum optical information using polariton wave packet propagated in the cavity array is examined. To take
into account decoherence processes in polaritonic system the quantum Brownian particle model is discussed as