Cooling atoms into condensates is slow and inefficient, and more than 99 percent of the atoms in the original cloud are lost in the process.
Now, MIT physicists have invented a new technique to cool atoms into condensates, which is faster than the conventional method and conserves a large fraction of the original atoms.
The team used a new process of laser cooling to cool a cloud of rubidium atoms all the way from room temperature to 1 microkelvin, or less than one-millionth of a degree above absolute zero.
Vuletić and his colleagues found a way to get around the initial limitations of laser cooling, to cool atoms into condensates using laser light from start to finish – a much faster, atom-conserving approach that he describes as a “Longstanding dream” among physicists in the field.
The team then aimed a second laser at the much-compressed cloud, which was tuned in such a way that the photons, when absorbed by the slower atoms, removed the atoms’ total energy, cooling them even further.
The team found that with their laser cooling technique, they were able to cool rubidium atoms from 200 microkelvin to 1 microkelvin in just 0.1 seconds, in a process that is 100 times faster than the conventional method.
What’s more, the group’s final sample of Bose-Einstein condensates contained 1,400 atoms, from an original cloud of 2,000, conserving a much larger fraction of condensed atoms compared with existing methods.