© Mike Matthews, JILA.
Atomic physics experiments routinely trap clouds of atoms, as described in Unit 5, but the atoms in these gas clouds are all distinct entities with separate quantum mechanical wavefunctions. This unit will describe how it is possible for the wavefunctions of all the atoms to merge into a single, macroscopic quantum state. This occurs when the interactions between the atoms are exactly the right strength and the atoms are very cold. The figure above shows three false color images of trapped atoms. The fastest atoms are colored red, and as they slow down their colors change to yellow, green, blue, and finally white. Moving from left to right, the three images show successive stages of cooling leading to the majority of atoms being in a single macroscopic quantum state in the trap at a temperature of ~10-8 K. The 2001 Nobel Prize in physics was awarded to Carl Wieman, Eric Cornell, and Wolfgang Ketterle for first creating these special quantum gases in their laboratories. (Unit: 6)