This slows down the movement, and hence the temperature, of its atoms to a fraction of a degree above absolute zero.

ECONOMIST: An old thought experiment may soon be realised

Dr Cornell and Dr Wieman had to plumb the icy depths of 20 billionths of a degree above absolute zero in order to win their prize.

ECONOMIST: The 2001 Nobel prizes: Playing catch-up | The

These atoms are cooled to a temperature of only a few billionths of a degree above absolute zero, the coldest possible temperature, at which all motion stops.

BBC: A Bose-Einstein condensate: It slows down light