  The polarization analysis of quantized probe light transmitted through an
atomic ensemble has been used to prepare entangled collective atomic states. In
a "balanced" detection configuration, where the difference signal from two
detection ports is analyzed, the continuous monitoring of a component of the
Stokes field vector provides a means for conditional projective measurements on
the atomic system. Here, we make use of classical driving fields, in the pulsed
regime, and of an "unbalanced" detection setup (single detector) where the
effective photon number of scattered photons is the detected observable.
Conditional atomic spin squeezed states and superpositions of such squeezed
states can be prepared in this manner.
