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DWC Profiles Investigator Mikkel Andersen

World record for controlling individual atoms

Mikkel_Andersen_webIn 2016, DWC Principal Investigator Mikkel Andersen achieved the world record for controlling individual atoms. In his Otago University laboratory he and his group have developed a ‘push button’ system that uses lasers to isolate a single atom, hold it in place, and cool it to its lowest quantum state. All this happens within a second of pressing the button. The result, which was published in March 2017 in Physical Review A, has generated significant international and local news coverage.

This fundamental research is laying the ground for the next generation of quantum technologies. It will allow researchers to do extremely controlled experiments which reveal hidden details of the quantum world. Understanding interactions between individual atoms could help to harness and amplify quantum properties so they can be utilised on a macroscopic scale. It could, for example contribute to the development of quantum computers capable of solving extremely complex problems. It could also enable the creation of completely new compounds and molecules with structures of atoms not found in nature or chemistry.

In 2010, Mikkel’s group was first in the world to isolate a single neutral Rubidium-85 atom and photograph it. Since then they have had to overcome two major challenges. Each experiment begins with a small cloud of atoms floating in the laser trap. The first challenge was to find a reliable way to evacuate all but one. The second challenges was to cool it down and precisely define its state of motion.

"Just as teams play off till a winner is found, they set up the experiment so that atoms knock each other out of the trap until only one remains."

Inspiration came from watching the Rugby World Cup. Using this approach, they have achieved an impressive 91% success rate of capturing an atom compared with 50% achieved by prominent overseas groups. They also managed to do it with cheap lasers used in CD players rather than the expensive ones commonly used.

They knew the second challenge of cooling an atom down to its lowest quantum state was possible because it had been achieved overseas. These groups had used a technique called Raman Sideband Cooling, which applies the force of laser light to slow the atom to a standstill. The problem was that Mikkel’s lab, unlike the highly funded overseas ones, had no way of eliminating magnetic noise, which would disrupt the experiment. So Mikkel developed a variation of the technique which is immune to magnetic noise. It is called Zeeman Insensitive Raman Sideband Cooling. Not only is it more versatile than the original technique, it achieves record results.

With these two techniques of capturing and cooling atoms, they achieve a 73% success rate of getting a single atom in its lowest quantum state. This is the highest degree of control in the world.