Plate Nº 72 · recorded October 10, 2026
PhysicsReported finding
Singapore team builds world's most accurate atomic clock
Singapore's Centre for Quantum Technologies reports a lutetium atomic clock with 1 × 10⁻¹⁹ uncertainty, the lowest for any optical clock. A two-clock comparison at 5.7 × 10⁻¹⁹ is also a record.
By James Calloway3 min read691 words
In brief
- Clock reached an uncertainty of 1 × 10⁻¹⁹, the lowest reported for any optical atomic clock
- Two lutetium clocks agreed to 5.7 × 10⁻¹⁹ — the most precise clock comparison on record, after 200 hours of measurement
- Result published in Nature on Sept. 23 by CQT team led by Murray Barrett
- Each clock uses a single ¹⁷⁶Lu⁺ ion and a laser at 848 nanometers, with the transition read to 19 decimal places
- International body weighing optical clock data toward a redefinition of the second expected in or after 2030
A lutetium-based atomic clock at Singapore's Centre for Quantum Technologies has reached an uncertainty of 1 × 10⁻¹⁹, the lowest reported for any optical atomic clock. The team published the result in Nature on Sept. 23.
The same experiment also produced the most precise two-clock comparison on record: a pair of lutetium devices agreed to within 5.7 × 10⁻¹⁹ after 200 hours of measurement.
"I am confident that what we have now is the most accurate clock in the world," says team leader Murray Barrett, a principal investigator at CQT and associate professor at the National University of Singapore.
Each clock traps a single ¹⁷⁶Lu⁺ ion matched to a laser wavelength of 848 nanometers. The ion's electron transition, measured to 19 decimal places, is the pendulum.
How does an atomic clock keep time?
Atomic clocks count seconds by locking a laser to a fixed property of atoms: the frequency at which an electron jumps between two energy levels. The laser's light waves swing like a pendulum, ticking off time.
Cesium has set the global standard since the 1960s. Cesium clocks already synchronize GPS, telecommunications and transport networks. But cesium's microwave frequency caps accuracy.
That limit pushed labs toward "optical" clocks, built on elements whose transitions oscillate at visible-light frequencies. Ytterbium, strontium and aluminum have all posted record-setting results in recent years.
The international body responsible for time standards is weighing data from these clocks toward a redefinition of the second expected in or after 2030.
Why lutetium?
Barrett's group began working with the rare-earth element more than a decade ago, betting that its clock transition would resist environmental noise that drags down rival designs. CQT says it is the only team pursuing lutetium for timekeeping.
"In the future, I just don't see how this clock can be beat," Barrett says.
Lutetium's clock transition barely shifts with temperature or magnetic field. "The good properties mean that high accuracy can be achieved even in a wide range of environments," Barrett says. "The lutetium clock would be stable even if you went from the hottest place recorded on Earth in Death Valley to the coldest place in the Antarctic plateau."
To isolate that signal, the team invented a method called hyperfine averaging — more than ten years of precision engineering in the making.
Why build two clocks?
One clock cannot test itself. To prove reproducibility, the team built a second lutetium clock and compared the pair using a technique called correlation spectroscopy.
"There is a humorous saying that 'A man with a watch knows what time it is. A man with two watches is never sure,'" says Dr. Kyle Arnold, a senior research scientist at CQT and joint first author. "It basically tells you that the only way to test the accuracy of a standard is to compare clocks and demonstrate reproducibility."
The two clocks, sitting on the same table, agreed to within 5.7 × 10⁻¹⁹ — the tightest match yet reported, according to the paper.
That comparison already bumps against a hard limit of physics. Optical clocks this sensitive can detect the slowing of time caused by gravity across millimeter-scale height differences. The team's measurement was sharp enough to resolve a 5 mm gap between the two ions. The researchers measured that height gap independently to within one millimeter so it would not contaminate the result.
What comes next?
Direct comparison with other top optical clocks remains out of reach. Scientists do not yet know the gravity differences between distant labs precisely enough to compare clocks at the 10⁻¹⁹ level.
The CQT team's answer is portability. "The next step is to take the lab-scale clock and miniaturize it into a transportable system," says Michael Lee, joint first author and a Ph.D. student on the NUS team. The researchers expect they can shrink the device without sacrificing accuracy.
A portable lutetium clock could let laboratories put rival designs side by side, sharpen models of Earth's gravity, and probe unknowns in fundamental physics. A redefinition of the second could follow, if other groups reproduce the result.
via Phys.org Physics (Source)
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Staff writer covering marketplaces and e-commerce at SciBeat.
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