Oakland, CA
1/22/01
Journal of Nature

In a most remarkable bit of science, the Journal of Nature is reporting that Lene Hau and colleagues at the Rowland Institute for Science in Cambridge, Massachusetts, have stopped light--not just slowed it down, but actually stopped it.

Light can be slowed down when it passes from air into denser materials--witness a light ray bending as it passes through water or glass. The slowing is very small; to slow light significantly requires a material in which quantum interference effects are important, leading to an extremely large nonlinear refractive index.

Hau and colleagues cooled a gas of magnetically trapped sodium atoms to within a few millionths of a degree of absolute zero. The gas is normally opaque to light; but it can be made transparent by illuminating it with a laser beam called the coupling beam, thereby allowing a 'probe' laser pulse to pass through it. This process is called electromagnetically induced transparency.

If the coupling laser is turned off while the probe pulse is in the gas cloud, the probe stops dead in its tracks. If the coupling beam is later turned back on, the probe pulse emerges intact, just as if it had been waiting to resume its journey. The researchers anticipate that their method of stopping light might one day be used for storing and shipping data in super-powerful 'quantum computers'.

But there are far more application for this technique than they theorize openly. Some are very scary indeed. Some are very promising as well. []