All-Electromagnetic Control of Broadband Quantum Excitations Using   Gradient Photon Echoes
  A broadband quantum echo effect in a three level $\varLambda$-type system interacting with two laser fields is investigated theoretically. Inspired by the emerging field of nuclear quantum optics which typically deals with very narrow resonances, we consider broadband probe pulses that couple to the system in the presence of an inhomogeneous control field. We show that such a setup provides an all-electromagnetic-field solution to implement high bandwidth photon echoes, which are easy to control, store and shape on a short time scale and therefore may speed up future photonic information processing. The time compression of the echo signal and possible applications for quantum memories are discussed. 
Wen-Te Liao and Christoph H. Keitel and Adriana P\'alffy
quant-ph physics.atom-ph