Researchers have built the world’s first nuclear clocks, using thorium-229 crystals and ultra-precise lasers to track time through atomic cores rather than electron clouds. Published in the journal Nature, the twin timepieces promise breakthroughs in GPS positioning, dark matter detection, and fundamental physics.
Two independent research teams have constructed the world’s first working nuclear clocks, altering precision timekeeping. The devices keep time by tracking tiny changes in the center of atoms rather than relying on the electron clouds used by traditional atomic instruments. While their current iteration does not yet surpass the absolute accuracy of the finest operational atomic clocks, both teams expect performance improvements.
University of New South Wales physicist Victor Flambaum noted that nuclear clocks possess the potential to become the most accurate instrument humans have ever built
. The findings from both groups were published in Nature, detailing devices built around thorium-229 nuclei embedded within crystals.
Beijing and Vienna Teams Test Competing Nuclear Clocks
Initial data from the two instruments reveal distinct performance markers. According to papers released by the journal Nature, the timekeeper developed by Chinese scientists led by Tsinghua University in Beijing demonstrates roughly six times the stability of the European counterpart built at TU Wien. The Beijing team also demonstrated that two crystals grown independently maintained identical time, indicating high reproducibility for future manufacturing.
The European team, meanwhile, utilized its device to search for dark matter. Thorsten Schumm, a physicist at Vienna University of Technology and a co-author on the European study, described the dynamic as a fierce but friendly global competition
when discussing the parallel developments with international colleagues.
Researchers Clear Decades of Engineering Hurdles
Although the foundational proposal for nuclear clocks originated more than twenty years ago—building on a 2003 proposal suggesting that atomic nuclei could serve as a particularly accurate way of building clocks—practical execution remained blocked by technical hurdles. Dr. Shiqian Ding, a physicist and study co-author at Tsinghua University, explained the complexity of the engineering effort.
“There was no single step that suddenly made the clock possible,” Dr Ding said. The problems included making a material with the right clock nuclei inside it and developing lasers precise enough to produce reliable changes.
Shiqian Ding, Tsinghua University physicist and study co-author
A turning point occurred in early 2024, when the TU Wien team successfully used a laser to prompt an atomic nucleus to change states, creating the initial “tick” of a nuclear clock. Both research groups ultimately selected a specific isotope, thorium-229, because its low energy state makes its transitions easier to track and manipulate under ultra-precise lasers.
Crystals Shield Against Interference and Enable Miniaturization
Conventional atomic clocks measure frequency by tracking electrons as they shift between energy states in caesium atoms. However, these standard instruments are approaching physical limits. They are also vulnerable to external interference, as external electric fields can affect their operation and reduce long-term reliability.
In contrast, atomic nuclei are approximately 100,000 times smaller than whole atoms. Because of this scale, they remain far less sensitive to stray electric fields. Professor Schumm noted that thorium-229 holds potential to be more stable than atomic clocks, opening the door to hardware miniaturization.
“We envision a chip-scale device,”
Thorsten Schumm, Vienna University of Technology physicist
He added that nuclear clocks could become very small and practical to move around.
Scientists Apply New Clocks to Navigation and Physics
The extreme precision promised by nuclear timekeeping opens multiple avenues for fundamental physics and applied technology. Improved clocks could improve navigation systems such as GPS, which has generated military interest in the latest iterations of atomic clocks. Beyond navigation, the instruments are sensitive enough to measure minute variations in time caused by gravitational fields, aligning with Einstein’s theories of relativity.
Professor Flambaum suggested that measuring gravitational gradients accurately could aid in mining exploration and earthquake forecasting. Both teams also emphasize the utility of the clocks in probing cosmology. Dr. Ding highlighted the potential to test fundamental physics, while the Vienna team has already used its proof-of-concept clock to search for elusive dark matter.