Wizardry at Harvard: Physicists Move Light

Wizardry at Harvard: Physicists Move Light
New York Times (02/08/07) P. A11; Craig, Kenneth

A Harvard study has demonstrated a technique for capturing, moving, and releasing a light pulse, which one day could allow computers to process information stored in light pulses. Study leader Lene Vestergaard Hau has had previous success with slowing down light, and even stopping it in what is known as Bose-Einstein condensate, a substance generated by bringing a cloud of sodium atoms down to an extremely low temperature. After a laser is shined on this cloud, it becomes molasses-like when hit by a second pulse. Hau's latest work went a step further: After being trapped in a Bose-Einstein condensate "cloud," the light pulse was transferred to another cloud and regenerated there. When the initial pulse hit the cloud, tens of thousands of sodium atoms were sent spinning in a clump that slowly moved forward; this clump had identical characteristics to the light pulse, even though it consisted only of sodium atoms. After this clump had imbedded itself within another Bose-Einstein condensate cloud, a laser was shined on this cloud, and a new pulse of light was produced, identical to the original one. This work shows the ability to "put [information] on the shelf," according to Hau, by making a light pulse into a clump of atoms. Atomic clumps would be far easier for a computer to work with compared to fast-moving light pulses. While these results are far from being used in any practical application, it does provide a "missing link," Hau says. Today, optical signals must be changed into electrical ones to be processed and then transformed back into light, but all-optical devices could lower costs and power usage.