Image of atomic beam device with a peanut for scale. Rb vapor in the source cavity feeds a buried microcapillary array and forms an atomic beam (indicated by a red-to-blue arrow) in the drift cavity. Credit: Nature Communications (2023)

Alexander Staron (left), William McGehee and Gabriela Martinez worked together on a new chip-scale version of an atomic beam clock, a tiny fraction of the size of the original instrument shown here. McGehee is a NIST scientist, and Staron and Martinez are CU Physics graduate students in PREP. Credit: R. Jacobson/NIST

Gaby and Alex’s team developed a chip-scale atomic clock (CSAC) that is a little larger than a peanut. Rubidium atoms in the atomic beam provide the microwave quantum transition that is used by the clock to provide a relative frequency stability of 1.2×10^(-9)/√Hz. The device uses the 6.8GHz ground state splitting of ⁸⁷Rb as the reference frequency. The device uses a microfabricated channel array developed at Georgia Tech, which reduces interactions with background air molecules so that the Rb atoms can traverse the 1 cm-long device without a collision. Their device improves on previous CSAC’s with much lower timing drift, with a goal of sub-microsecond timing error over several days. Possible applications are atom interferometry, Rydberg atom electrometry, and underwater exploration where GPS signals do not reach by using precise time-of-flight sonar soundings from GPS-equipped buoys.

From Rebecca Jacobson's article featured on phys.org:

"NIST has been using atomic beams for timekeeping since the 1950s. For decades, beam clocks were used to keep the primary standard for the second, and they are still part of NIST's national timekeeping ensemble. Beam clocks are precise, stable and accurate, but they're currently not the most portable. Smaller commercial clocks about the size of a briefcase are common, but they still require a significant amount of power (about 50 watts) to run. For comparison, smartphones require about a third of a watt for typical operation. Chip-scale atomic clocks (CSACs) were developed by NIST in 2001. "The CSAC is low-power and has high performance given its size. It's a wonderful device, but it does drift after running for a few thousand seconds," said William McGehee, a physicist at NIST."

Gaby is a fifth-year physics graduate student from Cal Poly Humboldt University. She joined PREP in 2019 and plans to graduate next year. Alex is a third-year physics graduate student from Miami University in Oxford, Ohio, and joined PREP in 2022. 

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