  We propose a quantum memory protocol based on dynamically changing the
resonance frequency of an ensemble of two-level atoms. By sweeping the atomic
frequency in an adiabatic fashion, photons are reversibly transferred into
atomic coherences. We present a polaritonic description for this type of
storage, which shares some similarities with Electromagnetically Induced
Transparency (EIT) based quantum memories. On the other hand the proposed
memory is also linked to the Gradient Echo Memory (GEM) due to the effective
spatial gradient that pulses experience in the medium. We discuss a possible
implementation of the protocol in hollow-core photonic crystal fibers.
