Singapore Researchers Report World’s Most Accurate Atomic Clock

The most accurate clock ever reported isn’t a wall clock or a satellite-borne device. Instead, it’s a single-charged atom, precisely standing on a tabletop in Singapore, with a laser tuned to an invisible light spectrum probing it. Indeed, this singular atom constitutes the entire timekeeping mechanism underlying the claim. Researchers state it would drift by no more than a second over 300 billion years, a timeframe around 20x longer than the current age of the universe.

The team at Singapore’s Centre for Quantum Technologies published these findings in Nature on September 23, 2026, indicating the work is peer-reviewed.

The Instrument and Its Scale

The instrument is a single-ion optical atomic clock. Each clock utilizes a single charged lutetium-176 ion, with its clock transition occurring at a laser wavelength of 848 nanometers. This represents laboratory-scale metrology, and a benchtop setup operating in a controlled environment.

Two key measured figures substantiate the claim. Specifically, the team established the frequency of one lutetium clock with a fractional uncertainty of 1 x 10⁻¹⁹, which they report as the lowest for any optical atomic clock to date. They then constructed a second identical clock and compared the two over 200 hours. The pair agreed to 5.7 x 10⁻¹⁹, marking the most precise clock comparison on record. These are experimental results.

Achieving Such Precision

An atomic clock operates by repeatedly querying an atom. An electron within the atom can transition between two energy levels, a jump that occurs at a specific, fixed frequency determined by physics. A laser is then tuned to precisely match this frequency, and the oscillations of the light itself become the timekeeping pendulum.

It’s like counting the crests of an exceptionally stable light wave as they pass. A faster wave provides a finer measurement. Optical clocks like this one operate at frequencies significantly higher than the caesium microwave standard that has defined the second since the 1960s, which enabled them to measure time with much greater precision.

Achieving nineteen decimal places of precision requires a series of engineering steps:

• Trapping and holding a single 176Lu+ ion to minimize its motion.
• Cooling the ion to prevent thermal motion from affecting the measurement.
• Locking an 848 nm laser onto the ion’s clock transition.
• Applying “hyperfine averaging,” a method developed by the team to clearly define the transition.
• Performing correlation spectroscopy across two clocks to measure their agreement.

Meanwhile, lutetium offers a distinct advantage: its clock transition is minimally affected by temperature or magnetic fields, factors that can shift the frequency of other atoms. Team leader Murray Barrett states the clock would remain stable when moved from Death Valley to the Antarctic plateau. The group has focused on lutetium for over a decade and believes they are the only ones currently using it for timekeeping.

The Data Supporting the Claim

Here are the specific, measured figures reported in the paper:

• Single-clock fractional uncertainty: 1 x 10⁻¹⁹, equivalent to a drift of no more than one second in 300 billion years.
• Clock-to-clock agreement: 5.7 x 10⁻¹⁹, equivalent to one second in 55 billion years.
• Comparison duration: 200 hours.
• Atomic reference: one 176Lu+ ion per clock, utilizing an 848 nm transition.

All this information originates from the Nature paper and the NUS release. It’s important to distinguish between accuracy and stability. Accuracy addresses how closely the clock matches the true transition frequency, while stability concerns how consistently it maintains that rate over time. The uncertainty budget relates to accuracy, and the Nature paper details the systematic shifts that were mitigated, although specific magnitudes are not reproduced here.

Record-Breaking Performance

The recent leaderboard has featured ytterbium, strontium, and aluminum optical clocks from labs such as NIST and JILA, all achieving precision in the 10⁻¹⁸ range. Lutetium’s entry at 10⁻¹⁹ surpasses these in accuracy, assuming the figure withstands independent scrutiny.

A fascinating aspect of such precise clocks is their sensitivity to gravity. They can detect time dilation caused by height differences as small as a few millimeters. The Singapore pair could resolve a 5mm height difference between two clocks on the same table, leading the team to measure the ions’ vertical positions below the millimeter level to account for this. 

Comparing these clocks with other leading clocks globally is more challenging, as differences in Earth’s gravity between locations are not yet mapped with sufficient precision.

Applications of Such a Clock

This level of precision transforms a clock into an instrument for measuring gravity. Two clocks at slightly different heights will tick at measurably different rates—a tangible demonstration of relativity on a benchtop. This opens possibilities for geodesy: mapping elevation and mass distributions across Earth by comparing time. 

These clocks contribute data towards a potential redefinition of the SI second after 2030, alongside other optical clock contenders. Additionally, precise timing is fundamental for secure network synchronization, a distinct layer from post-quantum cryptography under NIST FIPS 203/204/205, and separate from QKD and QRNG, which serve different functions entirely.

The ultimate validation for this record won’t be a stronger adjective, but rather an independent lab building a comparable clock, comparing it against Singapore’s, and publishing a matching uncertainty budget. According to PhD student Michael Lee, the next practical step is to miniaturize the setup into a transportable device without compromising its accuracy. Until another group confirms these findings, the superlative rests on two atoms on one table, demonstrating remarkable agreement with each other.