"Efficient Coupling of Atoms and Light"
James K. Thompson
Massachusetts Institute of Technology
Wednesday, March 1, 2006, 11-12 Noon in 375 LeConte Hall
Abstract
The long coherence times of trapped atoms makes them ideal storage media for quantum
information. In contrast, photons can rapidly transport quantum information, but are poorly suited
for storage. We will discuss progress using laser-cooled atomic ensembles in low finesse
optical cavities to strengthen the matter-light interaction with the ultimate goal
of efficient exchange of quantum information between the two media. In this work, collective
spin-gratings within the ensemble are used to store an excitation and convert it "on demand"
into a photon in a mode amendable to fiber coupling and transport. We observe >50% peak
conversion efficiencies of the stored excitation, as well as large sub-poissonian
correlations with the initial herald photon that signals the spontaneous creation of a spin-grating.
The quantum memory aspect makes this system useful for applications such as quantum repeaters and triggerable
single photon sources. Operating at zero delay time, the system acts as a source of photon pairs with
spectral brightness three orders of magnitude greater than achieved with nonlinear crystals.
Lastly, the near indistinguishability of the generated photon pairs is demonstrated via a simple two-photon
interference experiment.
