Brian DeMarco and Deborah Jin used a pair of magneto-optical traps to confine about 700000 atoms of potassium-40 at temperatures below 300 nanokelvin. This is about half of the degeneracy temperature for a gas of fermions. At these temperatures the occupation of the lowest quantum states increases from around zero to about 60%. The quantum degeneracy was observed as a barrier to evaporative cooling of the sample and a change in its thermodynamic behaviour. Measurements of the momentum distribution and total energy of the gas also revealed its quantum statistics.

A big challenge faced by DeMarco and Jin was cooling the gas. Most cooling techniques rely on collisions between the atoms for cooling, but since two identical fermions cannot be in the same place at the same time, the collisions needed for cooling cannot happen. The NIST team overcame this problem by placing the atoms in different magnetic sublevels. Atoms in the different sublevels were no longer identical and could therefore collide.