China’s Tsinghua University, working with multiple domestic research teams, has developed a "nuclear optical clock," becoming the first in the world to advance quantum precision measurement from electronic transitions to nuclear transitions. This opens new technological pathways for next-generation high-performance time-frequency standards. The findings were recently published in Nature.

The most precise atomic optical clocks to date work by recording the rhythm of electron transitions within atoms, but they require meticulous control of interference from electric fields, magnetic fields, temperature, and laser systems, and operate mainly in laboratories. The Tsinghua team spent nearly five years developing an original 148-nanometer continuous-wave vacuum ultraviolet laser technology, shifting the timekeeping reference to the nuclear transition inside the thorium-229 nucleus. The nucleus beats 2 quadrillion times per second, dividing time exceedingly finely—counting these beats yields the precise time.

The nuclear optical clock raises timekeeping precision to a new level and is expected to move beyond the laboratory into real-world applications such as navigation and deep space exploration, enabling more precise positioning and ranging of satellites and spacecraft to serve major national needs.