Chinese researcher pushes US ahead in race to build ultra-precise nuclear clock

Graduate student Zhang Chuankun helps lab pinpoint laser frequency to drive timekeepers that could test foundations of physics

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A vacuum ultraviolet frequency comb is a laser device that “acts like a ruler for light”, in the words of Chinese graduate student Zhang Chuankun. Photo: Ye Labs, JILA, NIST and the University of Colorado Boulder

Published: 6:00am, 19 Sep 2024

A graduate student from eastern China is at the centre of a major advancement in precision timekeeping, ending a decades-long search for an essential piece of the puzzle of building a nuclear clock.

Zhang Chuankun was listed as first author of a study, published in the journal Nature earlier this month, that could help pave the way for ultra-precise timekeepers.

Zhang’s co-authors include his mentor, the Chinese-American physicist Jun Ye, and a team from the US National Institute of Standards and Technology (NIST) and the University of Colorado Boulder.

Ye, a pioneer in ultra-precise timekeeping credited with building the world’s most accurate atomic clock, said Zhang was among “the very best” students he has worked with.

Zhang, a native of Shandong province, was instrumental in developing a special laser device known as a vacuum ultraviolet (VUV) frequency comb at Ye’s lab at JILA, a joint institute of NIST and CU Boulder.

“An optical frequency comb acts like a ruler for light,” Zhang said. “It allows for extremely accurate frequency measurements by comparing unknown frequencies to a known standard.”

His work enabled Ye’s lab, which began developing the comb in 2005, to pinpoint the precise laser frequency needed to trigger a nuclear transition and drive a nuclear clock.