It's nifty to look into the chamber and see a clump of ultracold atoms floating there," Hau says. "In this odd state, light takes on a more human dimension; you can almost touch it."
She and her team continued to tweak their system until they finally brought light to a complete stop. The light dims as it slows down, so you think that it's being turned out. Then Hau shoots a yellow-orange laser beam into the cloud of atoms, and the light emerges at full speed and intensity.
Inspired by Hau's success at slowing light, researchers working on a wooded hill a few miles away at the Harvard-Smithsonian Center for Astrophysics (CfA) used a similar technique to stop, then restart, a light beam. That team was headed by Ronald Walsworth and Mikhail Lukin, both associates of Harvard College. Their success was independent of Hau's effort.
"We didn't have much contact," she notes, "just a few e-mails.