  A novel method of multi-bit quantum optical data storage is presented, where
the storage time can be lengthened far beyond the spin phase-decay time in a
reversible spin inhomogeneous system excited by consecutive resonant Raman
optical data pulses. The ultralong storage time is obtained by an optical
population locking mechanism of modified rephasing process. This gives
potentials to quantum repeaters utilizing quantum memories for long distance
quantum communications, in which ultralong storage time plays a major role.
