The magneto-optical trap, or MOT, is the workhorse of cold-atom physics. Without this complex arrangement of laser beams and magnetic fields, the act of cooling atoms to just above absolute zero – and observing the quantum effects that emerge – would be nigh-on impossible. But before cold atoms can become part of a quantum sensor, quantum computer, or any other device that puts their quantum nature to practical use, this bulky old workhorse needs to become more like a pit pony: robust enough to do the job, yet much, much smaller.

Physicists at the US National Institute of Standards and Technology (NIST) have now taken an important step towards this goal. Led by William McGehee, the researchers used flat, lithographically-produced optics to create a MOT optical assembly just 15 cm long. While this is still too big for a practical cold-atom-based device, it is significantly smaller than the dinner-table-sized sprawl of ordinary MOTs, and a sign of how integrated photonics enables new designs. “Ultimately, what we’re trying to develop is something that is not just a small version of a laboratory experiment,” McGehee says. “You have to find different ways of doing the same things.”

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