Bose–Einstein condensate
A Bose–Einstein condensate (BEC) is a state of matter of a dilute gas of bosons cooled to temperatures very close to absolute zero (that is, very near 0 K or −273.15 °C). Under such conditions, a large fraction of bosons occupy the lowest quantum state , at which point macroscopic quantum phenomena become apparent. It is formed by cooling a gas of extremely low density, about one-hundred-thousandth the density of normal air, to ultra-low temperatures. Due to the unique properties of the condensate, it was shown by Lene Hau [1] that light can either be stopped or slowed down significantly to the velocity of 17 meters per second, resulting in an extremely high refractive index. Resource from Wikipedia Bose–Einstein condensate