Researchers in Singapore have unveiled the world’s most accurate atomic clock, built using a single trapped ion of lutetium-176. The record-breaking device measures atomic transition frequency to 19 decimal places and is so precise it would lose only one second every 260 billion years.
Scientists at the Centre for Quantum Technologies (CQT) at the National University of Singapore have built a device that surpasses previous timekeeping records. Published September 23 in the journal Nature, the findings establish a new benchmark for optical atomic clocks with an uncertainty of 1 × 10⁻¹⁹.
The achievement edges out leading devices from the United States and China. According to regional reporting, the new lutetium instrument is roughly four times as accurate as a calcium-ion clock developed by the Chinese Academy of Sciences in Wuhan. It also bests an aluminum-ion clock unveiled by the US National Institute of Standards and Technology.
Lutetium Improves Atomic Clock Precision Against External Interference
Traditional atomic clocks keep time by locking onto an atomic transition, an event where an electron changes energy levels at a fixed frequency. A tuned laser matches that transition, and the resulting light oscillations act like a pendulum.
Cesium atoms have anchored international time standards since the 1950s and 1960s, setting the foundation for GPS, internet synchronization, and telecommunications. Newer optical clocks use elements like strontium, ytterbium, and aluminum to oscillate much faster, yielding higher precision.
Even ultraprecise atomic clocks face interference from external variables such as magnetic fields, gravity, and temperature swings. The CQT team selected lutetium-176 because its transition frequency is naturally resilient to those disruptions.
“The good properties mean that high accuracy can be achieved even in a wide range of environments,” Barrett says. “The lutetium clock would be accurate even if you went from the hottest place recorded on Earth in Death Valley to the coldest place in the Antarctic plateau.”
Murray Barrett, CQT Principal Investigator and Associate Professor in the Department of Physics at the National University of Singapore
The research group spent more than a decade investigating lutetium, inventing a technique called hyperfine averaging to further suppress environmental effects like gravitational shifts.
Verifying Precision Through Correlation Spectroscopy
To prove the clock’s capability, the Singapore laboratory built two separate lutetium instruments and matched their ticking across more than 200 hours using correlation spectroscopy.
The two independent clocks agreed within an uncertainty of 5.7 parts in 10¹⁹. That verification marks the most precise clock comparison ever reported.
“It basically tells you that the only way to test the accuracy of a standard is to compare clocks and demonstrate reproducibility.”
Kyle Arnold, Senior Research Scientist at CQT at NUS
Detecting Gravity Across Millimeters and Preparing for 2030 Standards
At the 10⁻¹⁹ precision tier, physics introduces new observational challenges. Einstein’s theory of general relativity states that gravity causes time to move more slowly, meaning clocks at different elevations tick at different rates.
The CQT instruments proved sensitive enough to detect gravitational time dilation across vertical distances of just 5 millimeters, or about 0.2 inches. Because Earth’s local gravity fields vary too much to map with matching precision, direct comparison against other distant world-class atomic clocks remains complicated.
The international body responsible for time standards is weighing optical clock data for a formal redefinition of the second targeted for or after 2030.
Before the lutetium clock can transition from a laboratory benchmark to a field instrument, engineers must shrink the hardware.
Researchers note that portable configurations could eventually map subtle variations in Earth’s gravitational field and test fundamental physics.