Now they've figured out how to make it stand still.
The breakthrough slowing light to a stop, storing it and then releasing it at will as if it were an ordinary particle has apparently been pulled off by two independent teams of physicists, one led by Dr. Ronald L. Walsworth and Dr. Mikhail D. Lukin of the Harvard-Smithsonian Center for Astrophysics, the other by Dr. Lene Vestergaard Hau of Harvard, who made similar headlines two years ago when she slowed a beam of light down to a nearly pedestrian 38 miles an hour. Walsworth's work will be published in the Jan. 29 Physical Review Letters; Hau's in the journal Nature, sometime soon.
How? Unsurprisingly, it's complicated. But the closely related techniques used by the two teams both involve canisters of chilled gas Walsworth's team used rubidium, treated with a pair of laser beams that rendered it transparent into which the light can enter without being absorbed. Instead, the first beam leaves its mark on the gas particles while the second beam is slowly turned down by the physicists. As that happens, the first beam grinds to a halt and goes dark.
But it's not gone. There's a record of the light beam stored in the gas atoms, and when the physicists zap the gas with another burst of light, the first one reappears in its original form (how they tell them apart is a physicist thing). And thus is light made to stop at a traffic light and wait, before being sent on its way.
Why bother? Well, if you had a suit made of rubidium canisters, you'd be invisible (except for the suit of rubidium canisters, of course). And solar power storage being the missing link when it comes to that sort of thing comes to mind. But most folks, when they think of taming light, dream of super-fast, super-small computers, and that seems to be where this all headed. A so-called quantum computer one that used light instead of electricity could use switching mechanisms moved by a single photon. Quantum communications could never be eavesdropped upon. Without the ability to control light, work in that field had run out of room. Now scientists appear to be well on their way to making light, nature's most elusive form of energy, do whatever they want it to.