Today’s fridges and air conditioners more often use a compressor, but absorption refrigerators still have their uses – science experiments included.
“Our device is the first implementation of the absorption refrigeration cycle on the nanoscale,” says co-author Stefan Nimmrichter.
To create an absorption fridge with just three atoms took exquisite control. “As an experimental scientist, it’s a pure joy to be able to manipulate individual atoms,” says Gleb Maslennikov, the paper’s first author.

First, the researchers caught and held three atoms of the element Ytterbium in a metal chamber from which they’d removed all the air. They also pulled one electron off each atom to leave them with a positive charge. The charged atoms – called ions – can then be held in place with electric fields. Meanwhile, the researchers nudge and zap the ions with lasers to bring them into their lowest energy state of motion. The result is that the ions are suspended almost perfectly still, strung out in a line.