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Physicists Split Ultracold Atom Clouds

Physicists at the University of Otago have developed steerable optical tweezers that use intense laser beams to precisely split minute clouds of ultracold atoms and smash them together.

The feat enhances efforts to understand how atoms interact at temperatures of less than a millionth of a degree above absolute zero, with potential applications including new tools to probe microscopic structures and sensors that can map minute variations in magnetic fields.

In research published in Optics Letters, the researchers used the technology to split a single ultracold cloud of rubidium atoms sequentially into 32 daughter clouds, spreading them out over nearly half a centimetre.

“This sort of precise control of these atoms is like being able to pull a delicate snowflake into two clean halves with your bare hands,” says lead researcher Dr Niels Kjaergaard. “It’s quite remarkable that we are able to manipulate such minute and fragile samples while moving them such a comparatively large distance.”

The researchers steered horizontal and vertical laser beams around with precisely controlled travelling acoustic waves. These steerable laser beams confine and move the atoms. As well as splitting atom clouds, the system allows them to be collided.

“Tongue-in-cheek, we like to refer to our set-up as the ‘Littlest Hadron Collider’,” Kjaergaard jests. “In some ways it’s the complete opposite of what is the world’s largest and most powerful particle collider, because instead of using extreme acceleration, we smash our atom clouds together at a pedestrian pace of up to a metre per second.”