Chinese researchers develop ytterbium lattice clock with record-breaking precision
A team of Chinese physicists has developed an optical lattice clock based on ytterbium-171 atoms achieving a total systematic uncertainty of 1.1×10⁻¹⁸ and a synchronous stability of 2.7×10⁻¹⁹ over roughly 60 hours of averaging. The clock employs an in-vacuum buildup cavity to boost lattice light power and an in-vacuum blackbody radiation shield to tightly characterize thermal frequency shifts. Clocks at this precision level underpin next-generation timekeeping standards, relativistic geodesy, and tests of fundamental physics.
Researchers from institutions in Shanghai and Wuhan, China, report an optical lattice clock using ytterbium-171 (¹⁷¹Yb) atoms that achieves a total systematic uncertainty of 1.1×10⁻¹⁸, placing it among the most accurate atomic clocks ever demonstrated. Two nearly identical clocks were compared synchronously, reaching a fractional frequency instability of 2.7×10⁻¹⁹ after 216,000 seconds of averaging. A key technical advance is the use of an in-vacuum optical buildup cavity to enhance the lattice trapping light, reducing the atoms' exposure to stray fields. The dominant uncertainty contribution comes from the blackbody radiation (BBR) Stark shift at 8.7×10⁻¹⁹, mitigated by an in-vacuum BBR shield that provides a well-characterized thermal environment. The team also precisely determined the magic lattice frequency ν_zero = 394,798,258.3(1) MHz, at which the lattice light shift on the clock transition is suppressed, with the residual lattice light shift uncertainty controlled to 3×10⁻¹⁹. The two clocks are intended for future remote optical frequency comparisons between Shanghai and Wuhan, which could enable relativistic height measurements and contribute to redefinition of the SI second. The preprint has been submitted to the journal Metrologia and has not yet undergone peer review.
What's missing
As a preprint submitted but not yet peer-reviewed, independent verification of the systematic uncertainty budget has not occurred. The paper does not detail the optical fiber or free-space link infrastructure planned for the Shanghai–Wuhan remote comparison, leaving the feasibility and timeline of that application unaddressed. Additionally, no direct comparison against other state-of-the-art clocks (e.g., Sr or Al⁺ systems at NIST, PTB, or SYRTE) is reported, making it difficult to independently benchmark the claimed performance.
What different sources said
- arXiv physicsCenter
Ytterbium lattice clock with uncertainty of $1.1\times 10^{-18}$ and instability of low $10^{-19}$
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