Researchers in Singapore have built a refrigerator that’s just three atoms big.
This quantum fridge won’t keep your drinks cold, but it’s cool proof of physics operating at the smallest scales. The work is described in a paper published in Nature Communications (“Quantum absorption refrigerator with trapped ions”).
Researchers have built tiny ‘heat engines’ before, but quantum fridges existed only as proposals until the team at the Centre for Quantum Technologies at the National University of Singapore chilled with their atoms.
The device is an “absorption refrigerator”. It works without moving parts, using heat to drive a cooling process.The first absorption refrigerators, introduced in the 1850s, cycled the evaporation and absorption of a liquid, with cooling happening during the evaporation stage. They were widely used to make ice and chill food into the 20th Century. Albert Einstein even held a patent on an improved design.

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.

Image Credit: Centre for Quantum Technologies, National University of Singapore

Read more at nanowerk.com

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