  A scheme is proposed to prepare squeezed states and Schr\"{o}dinger cat-like
states of the collective spin degrees of freedom associated with a pair of
ground states in an atomic ensemble. The scheme uses an effective
Jaynes-Cummings interaction which can be provided by excitation of the atoms to
Rydberg states and an effective J_x interaction implemented by a resonant Raman
coupling between the atomic ground states. Both dynamical evolution with a
constant Hamiltonian and with adiabatic variation of the two interaction terms
are studied. We show that by the application of further resonant laser fields,
we can suppress non-adiabatic transfer under the time varying Hamiltonian and
significantly speed up the evolution towards a maximally squeezed, J_z=0,
collective spin state.
