A team from Singapore’s Centre for Quantum Technologies, led by researchers at the National University of Singapore, has unveiled a lutetium-based optical clock that surpasses the cesium standard in precision, with an uncertainty around 1 x 10^-19 and the potential to be off by only one second over 300 billion years.

The Lu+ clock’s accuracy is driven by the high frequency of the transition and its robustness against temperature and magnetic-field perturbations, making it the most precise optical clock demonstrated to date.

Direct clock comparisons show two independent Lu+ clocks agreeing at the 5.7 x 10^-19 level over 200 hours, marking the most precise clock-to-clock comparison reported so far.

The methodology includes an interrogation sequence with optical and microwave steps and correlation spectroscopy, emphasizing equal population time across hyperfine states and phase-sensitive parity measurements to realize the HA frequency.

Beyond redefining time, the technology promises wide-ranging applications in fundamental physics, satellite navigation, internet synchronization, finance, and power-grid stability, with future use in gravity-related observations for geology and resource mapping.

Challenges remain, including moving from lab demonstrations to a transportable, compact clock and addressing long-term maintenance to enable practical adoption of a redefined second.

Extensive stress-testing of the quadratic Zeeman shift and analysis of environmental temperature bounds and RF heating show blackbody radiation remains the largest remaining single-clock uncertainty but is well-controlled.

Efforts are underway to miniaturize the clock and transition from a lab setup to a portable system suitable for field deployment, while preserving the demonstrated accuracy.

The Lu+ clocks could enable transportable, high-precision standards and facilitate broader adoption, with comparisons limited by geopotential differences in remote benchmarking.

Gravitational effects are accounted for by direct height-difference measurements of the ions, achieving millimetre-scale precision in relating time to gravity.

Lead researchers include Murray Barrett, Kyle Arnold, and Michael Lee, with the work published in Nature on September 23, 2026.

The push toward redefining the SI second is being driven by optical clocks using lutetium, ytterbium, strontium, and aluminium, as they probe gravity and fundamental physics phenomena.