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-ionisation 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.
Alex Kuzmich, a professor in the School of Physics at the Georgia Institute of Technology, explained: "We are able to convert Rydberg excitations to single photons with very substantial efficiency, which allows us to prepare the state we want every time. This new system offers a fertile area for investigating entangled states of atoms, spin waves and photons. We hope this will be a first step toward doing a lot more with this system."
Co-author Yaroslav Dudin added: "This new photon source is about a thousand times faster than existing systems. The numbers are very good for our first experimental implementation."