  Continuous change of the propagation direction of a classical control field
in the process of its off-resonant Raman interaction with a weak signal field
in a three-level atomic medium is suggested for quantum storage of a
single-photon wave packet. It is shown that due to phase matching condition
such an angular control allows one to reversibly map the single-photon wave
packet to the Raman spatial coherence grating. Thus, quantum storage and
retrieval can be realized without using inhomogeneous broadening of the atomic
transitions or manipulating the amplitude of the control field. Under some
conditions the proposed scheme proves to be mathematically analogous to the
quantum storage scheme based on controlled reversible inhomogeneous broadening
of the atomic states.
