Physicists outclassed by machine learning experiment

Experiment that shows BEC via ANU_Stuart Hay Experiment showing the small red glow of a BEC trapped in infrared laser beams (Photo credit: Stuart Hay at ANU)

Effective Bose-Einstein condensates (BECs) have been produced in a fraction of the time it would normally take physicists to achieve. How did they do it? Australian researchers employed machine learning principles in an online optimisation process.

A BEC is a state of matter of a dilute gas of atoms trapped in a laser beam and cooled to temperatures just above absolute zero. BECs are extremely sensitive to external disturbances, which makes them ideal for research into quantum phenomena or for making very precise measurements such as tiny changes in the Earth’s magnetic field or gravity.

The experiment, developed by physicists from ANU, University of Adelaide and UNSW ADFA, demonstrated that “machine-learning online optimisation” can discover optimised condensation methods “with less experiments than a competing optimisation method and provide insight into which parameters are important in achieving condensation,” the physicists explain in an open-access paper in the Nature group journal Scientific Reports.

Faster, cheaper than a physicist

The team cooled the gas to around 5 microkelvin. To further cool down the trapped gas (containing about 40 million rubidium atoms) to on the order of nanokelvin*, they then handed control of the three laser beams** over to the machine-learning program.

Optical dipole trap illustrating the 3 laser beams and the condensate_PB Wigley_Scientific Reports

Optical dipole trap illustrating the 3 laser beams and the condensate (red-yellow oval in blue square) (Photo credit: P. B. Wigley et al./Scientific Reports)

The physicists were surprised by the clever methods the system came up with to create a BEC, like changing one laser’s power up and down, and compensating with another laser.

“I didn’t expect the machine could learn to do the experiment itself, from scratch, in under an hour,” said co-lead researcher Paul Wigley from ANU Research School of Physics and Engineering. “A simple computer program would have taken longer than the age of the universe to run through all the combinations and work this out.”

Wigley suggested that one could make a working device to measure gravity that you could take in the back of a car, and the AI would automatically recalibrate and fix itself.

“It’s cheaper than taking a physicist everywhere with you,” he said.

* Billionth of a degree above absolute zero — where a phase transition occurs, and a macroscopic number of atoms start to occupy the same quantum state, called Bose-Einstein condensation.

** The 1064 nm beam is controlled by varying the current to the laser, while the 1090 nm beam is controlled using the current and a waveplate rotation stage combined with a polarising beamsplitter to provide additional power attenuation while maintaining mode stability.

Read this article in full at Kurzweil.Ai

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