BEIJING, 9th October, 2026 (WAM) -- Chinese scientists have developed a nuclear optical clock that measures time through energy changes inside atomic nuclei, a breakthrough that could lead to more accurate and portable timekeeping in navigation, deep-space exploration and fundamental physics research.
According to China Central Television (CCTV), researchers from Tsinghua University and several other Chinese institutions spent nearly five years developing the clock. Their findings were published in the journal Nature on Wednesday.
The team developed a continuous-wave vacuum-ultraviolet laser operating at 148.4 nanometres and used it to trigger a transition within the nuclei of thorium-229, a radioactive isotope. By locking the laser's frequency to the transition, they created a nuclear clock.
Nuclear optical clocks, which use transitions within the atomic nucleus as their reference, are seen as a potential successor to atomic microwave clocks and optical atomic clocks.
"A traditional pendulum clock swings about once a second, and we can tell how much time has passed by counting those swings. Our nuclear optical clock instead uses the rhythm of an atomic nucleus as its 'pendulum'. That rhythm is, of course, much faster than that of a wall clock, at about 2 quadrillion cycles per second. It divides time into extremely fine intervals, allowing us to measure time precisely by counting those cycles," said Ding Shiqian, Associate Professor in Tsinghua University's Department of Physics and an adjunct researcher at the Beijing Academy of Quantum Information Sciences.
The most accurate optical atomic clocks currently rely on electron transitions, which are sensitive to electric and magnetic fields, temperature changes and laser systems. These factors require strict controls, largely confining the most precise clocks to laboratories and limiting their miniaturisation and practical use.
"An atomic nucleus is tens of thousands of times smaller than the surrounding electron cloud, which makes its rhythm more stable. This means the nuclear optical clock we developed could eventually become even more precise. It may also be possible to make such clocks smaller. Once miniaturised, an ultra-precise timekeeping device could be put to practical use instead of remaining merely a laboratory tool," Ding said.
Researchers said the technology could eventually improve satellite positioning and spacecraft distance measurements, supporting navigation, deep-space exploration and other applications requiring highly accurate time and frequency standards.