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Physics

Sunlight could cool an atom to its coldest possible temperature

Sunlight transmitted through an optical fibre could be used to help cool a single charged atom to a temperature only a few millionths of a degree above absolute zero

By Karmela Padavic-Callaghan

26 May 2023

Sunlight coming out of the optical fibre

Sunlight coming out of an optical fibre

Amanda Younes

Sunlight could be used to cool a charged atom to its lowest temperature allowed by the laws of physics.

In the 1990s, several people won Nobel prizes for working out how to make atoms extremely cold with precisely controlled laser light. Now, Amanda Younes and Wesley Campbell at the University of California, Los Angeles, have found that some parts of the cooling process could be done with light straight from the sun.

The researchers calculated how a single positively charged barium atom, or ion, …

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