  We report complete characterization of an optical memory based on
electromagnetically induced transparency. We recover the superoperator
associated with the memory, under two different working conditions, by means of
a quantum process tomography technique that involves storage of coherent states
and their characterization upon retrieval. In this way, we can predict the
quantum state retrieved from the memory for any input, for example, the
squeezed vacuum or the Fock state. We employ the acquired superoperator to
verify the nonclassicality benchmark for the storage of a Gaussian distributed
set of coherent states.
