  Quantum interfaces between polarized atomic ensembles and coherent states of
light, applied recently to manipulate bipartite and multipartite entanglement,
are revisited by means of a continuous-variable formalism. The explicit use of
the continuous-variable formalism facilitates significantly the analysis of
entanglement between different modes, reducing it to the study of the
properties of a final covariance matrix which can be found analytically.
Furthermore, it allows to study matter-light interfaces for mixed states,
adapting the formalism to the experimental situations in which the initial
prepared Gaussian states are, unavoidably, affected by a certain amount of
noise. A multipartite scenario, leading to the generation of macroscopic
cluster states is presented and analyzed in detail within this formalism.
