Fast and efficient optical memory and manipulation in cold and ultracold atomic ensembles
The ability to store and manipulate quantum information encoded in electromagnetic (often optical) signals represents one of the key tasks for quantum communications and computation schemes. In the pursuit of a practical but efficient and broadband quantum memory, we make use of a three-level atomic system (in our case, laser-cooled rubidium atoms) and realize storage and photonic manipulations in the regime of “Autler-Townes splitting” (ATS), where a classical-level control field controls the absorption of an auxillary, possibly quantum, signal field. We demonstrate on-demand storage and retrieval of both high-power and less-than-one-photon optical signals with total efficiencies up to 30%, using the ground state “spin-wave” as our storage states. Recently, we began storing signals in much colder samples, approaching the transition to Bose-Einstein condensation. We also realize a number of photonic manipulations, including temporal beamsplitting, frequency conversion, and pulse shaping. The ATS memory scheme is inherently fast and broadband, and, in contrast to the related schemes, is less demanding in terms of technical resources, making it a leading candidate for practical quantum technologies.