Overview
- The Centre for Quantum Technologies at the National University of Singapore published Nature results on 23 September 2026 reporting a lutetium-ion optical clock measured to the 19th decimal with a reported uncertainty of 1×10^-19.
- The team built two independent lutetium clocks and used about 200 hours of correlation spectroscopy to compare them, finding agreement to 5.7×10^-19, the smallest uncertainty yet for a clock comparison.
- The clocks use a single charged 176Lu+ ion with a clock transition at 848 nm, operate at room temperature with commercially available lasers, and rely on techniques such as hyperfine averaging to reduce sensitivity to temperature and magnetic fields.
- Researchers say the result strengthens optical‑clock data being submitted to international time‑standards bodies for consideration of a post‑2030 redefinition of the SI second and that the next steps are to miniaturize the lab setup for transportable use.
- Optical clocks at the 10^-19 level are sensitive to gravitational time dilation over millimetre height differences, which complicates cross‑lab comparisons but also offers new opportunities for geodesy, navigation and tests of fundamental physics.