A Bose–Einstein condensate (BEC) is a state of matter formed by a system of bosons confined in an external potential and cooled to temperatures very near to absolute zero (0 kelvin or −273.15 °C). Under such supercooled conditions, a large fraction of the atoms collapse into the lowest quantum state of the external potential, at which point quantum effects become apparent on a macroscopic scale.
in a recent experiment, a pulse of light was slowed down to only 17 meters (55.7 feet) per second. Sound travels at 340 meters (1115 feet) per second in air.
The trick was to pass the light pulse through a cloud of extremely cold sodium atoms. The sodium atoms, which were cooled to a frigid 50 billionths of a degree above absolute zero, entered a special state called a "Bose-Einstein condensate." In this state, millions of atoms act as if they are one single atom.
The light pulse slowed down because it constantly exchanged energy with the atoms in the cloud. Upon leaving the cloud, it returned to its normal zippy pace. Scientists are excited by the experiment's implications for physics. It might also lead to new components for optical computers or other devices.