Wednesday, July 17, 2013

Light Stopped And Stored For More Than A Minute

Advances in this field of storing light have been astounding. It was only a few years ago that we had the amazing accomplishment of light being stopped and then "played back" out of Lene Hau's lab. And there have been more advances since then (read here). Now comes this latest paper (free access to the actual paper is available at that link).

There are two major accomplishment that are notable with this one:

1. They managed to store light and all of its coherent information for more than a minute, and

2. They are using a solid state medium, rather than atomic gasses, which will make this more viable for storing quantum information.

While solid-state devices would be preferable for applications, stopping light in solids is more challenging: stronger interactions between atoms and their environment severely limit the attainable coherence times. But the effect has been demonstrated in a special class of solids: crystals doped with rare-earth (RE) ions cooled at cryogenic temperatures. Since the atoms are naturally trapped in the crystal, the motion of RE atoms is limited and the transitions of interest take place between electronic levels (e.g., the 4f electrons of praseodymium) shielded from the crystal environment by outer full electronic shells (5s and 5p). This makes the coherence properties of these crystals exceptional.


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