  Recent experiments demonstrating atomic quantum memory for light [B.
Julsgaard et al., Nature 432, 482 (2004)] involve two macroscopic samples of
atoms, each with opposite spin polarization. It is shown here that a single
atomic cell is enough for the memory function if the atoms are optically pumped
with suitable linearly polarized light, and quadratic Zeeman shift and/or ac
Stark shift are used to manipulate rotations of the quadratures. This should
enhance the performance of our quantum memory devices since less resources are
needed and losses of light in crossing different media boundaries are avoided.
