Strontium optical lattice clock reports 8.1 × 10⁻¹⁹ total systematic uncertainty
What was demonstrated
An optical lattice clock using the ¹S₀ to ³P₀ transition in a dilute ensemble of fermionic strontium atoms, held in a shallow, vertically oriented one-dimensional optical lattice, reported a total systematic uncertainty of 8.1 × 10⁻¹⁹ in fractional frequency units. The authors state that all other systematic effects have uncertainties below 1 × 10⁻¹⁹. This is the authors' evaluation of one laboratory clock's error budget, not a measure of performance in the field.
Why it matters
Systematic uncertainty sets how closely a clock's tick can be tied to its ideal frequency, so a smaller bound is a step towards the accuracy a redefined second would need. This result describes one laboratory system and does not by itself show that optical clocks are ready to replace the caesium standard.
Caveats
- The 8.1 × 10⁻¹⁹ figure is the authors' error budget for one clock, evaluated in the laboratory. It is not a record of long-term operation.
- The paper revises the blackbody radiation shift correction using a re-evaluated lifetime, so the total figure depends on that revised correction.
- This result does not by itself redefine the SI second. Any redefinition would need international agreement, which this paper does not provide.
Technology profiles
Sources
- peer reviewed paper
Clock with 8×10⁻¹⁹ Systematic Uncertainty
Alexander Aeppli, Kyungtae Kim, William Warfield et al.. Physical Review Letters, 10 Jul 2024. DOI: 10.1103/PhysRevLett.133.023401.
Last reviewed 21 Oct 2026.