"They first cooled about 100,000 atoms to a positive temperature of a few nanokelvin, or billionth of a kelvin. They cooled the atoms within a vacuum chamber, which isolated them from any environmental influence that could potentially heat them up accidentally. They also used a web of laser beams and magnetic fields to very precisely control how these atoms behaved, helping to push them into a new temperature realm."
The scientists theorize that an understanding of absolute negative temperature could essentially allow us to escape the constraints of entropy and create engines that are more than 100% efficient.
Here's the link to the Science article (paywalled): http://www.sciencemag.org/content/339/6115/52"
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