  We derive and evaluate equations of motion for the mean values and variances
of the components of spins collectively coupled to a broadband squeezed
radiation reservoir. Our formalism bridges between a single two-level emitter,
represented by spin components that relax at different rates, depending on the
degree of squeezing, to an ensemble of emitters represented by a large
collective spin, whose components relax independently of the squeezing. For a
single spin, the steady state fluctuations in the transverse components are
independent of the squeezing, while the steady state of a large spin ensemble
reflects the statistics of the squeezed reservoir. This follows from an
analysis of the Langevin noise contributions to the equations of motion and
their consequences for the first and second moments of the spin operators. We
argue that the difference between a single and many spins is related to whether
vacuum fluctuations or radiation reaction dominate the coupling of the spin
system to the radiation environment.
