  Practical schemes for creation of multi-mode squeezed (entangled) states of
atomic ensembles located inside a high-Q ring cavity are discussed. It is
assumed that the cavity is composed of two degenerate mutually
counter-propagating modes that can simultaneously couple to the atomic
ensembles with the same coupling strengths. The ensembles are composed of
ultra-cold atoms which are modeled as four-level systems driven by two laser
fields, both co-propagating with one of the cavity directions. We illustrate a
procedure that constructs multi-mode squeezed states from the vacuum by a
unitary transformation associated with the collective dynamics of the atomic
ensembles subjected to driving lasers of a suitably adjusted amplitudes and
phases. The lasers pulses together with the cavity dissipation prepare the
collective modes in a desired stationary squeezed state.
