Quantum gas in free fall

In 2021 a team in Germany reported cooling a cloud of rubidium atoms to an effective temperature of 38 picokelvin, about 38 trillionths of a degree above absolute zero. They used a lensing technique on the gas while it floated in free fall in the Bremen drop tower, where nothing pulls the atoms down.

Record claims depend on how temperature is defined for a tiny quantum gas. Other labs quote very low figures by different methods, and true absolute zero cannot be reached.