Dark and bright polaritons in solids in the presence of excitonic resonances

We study the possibility to store and retrieve quantum information with use of "dark" and "bright" polaritons in solids with excitonic resonances. In a crystal with I >-type impurity atoms the upper level lying in the excitonic band of the crystal forms a Fano-type resonant state via configuration interaction with the continuum of crystal's excitonic band. Polariton states are introduced in case of transitions through excitonic resonance and the properties of these states are studied. We also investigate propagation of dark polariton and show that its shape and quantum state are preserved during propagation. Limiting cases of adiabatic and non-adiabatic turning-on the fields are analyzed in detail.