hypnosec writes "Scientists at the Georgia Institute of Technology Research have demonstrated a new technique for creating single photons for usage in optical quantum information processing. Researchers used a laser to excite a single atom in a cloud of ultra-cold rubidium gas. Atoms which have one or more electrons excited to a condition of near-ionization known as the Rydberg state have highly exaggerated electromagnetic properties, interacting strongly with one another. One Rydberg atom can stop the formation of further excited atoms within an area of 10 to 20 microns — which is known as the Rydberg blockade. The scientists found that if they confined the rubidium gas to an area covered by the blockade, they could ensure only one Rydberg atom would form when the laser hit the cloud. In other words, they could reliably create a single photon with well-known properties, which is important in a number of areas of research, including quantum information processing."
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