  Collective Rydberg excitations provide promising applications ranging from
quantum information processing, and quantum computing to ultra-sensitive
electrometry. However, their short lifetime is an immense obstacle in real-life
scenarios. The state-of-the-art methods of prolonging the lifetime were mainly
implemented for ground-state quantum memories and would require a redesign to
effectively work on different atomic transitions. We propose a protocol for
extending the Rydberg excitation lifetime, which in principle can freeze the
spin-wave and completely cancel the effects of thermal dephasing. The protocol
employs off-resonant ac-Stark lattice modulation of spin waves by interfering
two laser beams on the atomic medium. Our implementation showed that the
excitation lifetime can be extended by an order of magnitude, paving the way
towards more complex protocols for collective Rydberg excitations.
