Повільне та «зупинене» світло

In 1999, Lene Vestergaard Hau’s team measured a light-pulse propagation speed of just 17 m/s in ultracold sodium gas using electromagnetically induced transparency. This is the pulse’s group velocity in a specially prepared medium, not a change to the speed of light in vacuum (about 299,792,458 m/s). In 2001, researchers demonstrated stopping and restarting a light pulse: its quantum information was transferred to atomic excitations in the medium, rather than photons sitting motionless. The popular summary has a real basis, but “nearly stopped light” needs the qualification that it was a pulse in a medium that was halted.