  We report on an experiment in which orbital angular momentum of light is
mapped at the single-photon level into and out of a cold atomic ensemble. Based
on the dynamic electromagnetically-induced transparency protocol, the
demonstrated optical memory enables the reversible mapping of Laguerre-gaussian
modes with preserved handedness of the helical phase structure. The
demonstrated capability opens the possibility to the storage of qubits encoded
as superpositions of orbital angular momentum states and to multi-dimensional
light-matter interfacing.
