  Starting from the first principles of nonrelativistic QED we have developed
the quantum theory of the interaction of a two-component ultracold atomic
ensemble with the electromagnetic field of vacuum and laser photons. The main
attention has been paid to the consistent consideration of dynamical
dipole-dipole interactions in the radiation field. Taking into account
local-field effects we have derived the system of Maxwell-Bloch equations.
Optical properties of the two-component Bose gas are investigated. It is shown
that the refractive index of the gas is given by the Maxwell-Garnett formula.
All equations which are used up to now for the description of the behavior of
an ultracold atomic ensemble in a radiation field can be obtained from our
general system of equations in the low-density limit. Raman-Nath diffraction of
the two-component atomic beam is investigated on the basis of our general
system of equations.
