Chinese Scientists Develop Nuclear Clock for Ultra-Precise Timekeeping
Beijing (ANTARA) – Chinese scientists have developed a nuclear clock and achieved stable operation, shifting ultra-precise timekeeping from electron transitions within atoms to transitions within atomic nuclei, according to a research article published in the journal Nature, Xinhua reported on Friday (9 October).
Solid-state nuclear clocks could offer advantages in miniaturisation and engineering, and are expected to meet high-precision timing and frequency requirements in applications such as satellite navigation and deep-space exploration.
The clock uses a laser to trigger precise energy-level transitions in the nucleus of thorium-229, a particular radioactive isotope, and uses the frequency of those nuclear transitions as its time reference. The researchers built the device using a 148-nanometre continuous-wave vacuum-ultraviolet laser developed independently and a calcium fluoride crystal doped with thorium-229.
The new clock is expected to establish next-generation time and frequency standards and represents a significant breakthrough in quantum precision measurement, said Zhai Hui, head of the Department of Physics at Tsinghua University.
“The successful development and stable operation of the nuclear clock show that quantum manipulation capabilities have extended to the nuclear scale,” Zhai said.
Atomic clocks use transitions between particular energy levels of electrons within atoms as their frequency reference, making them the most accurate timekeeping devices available today. Nuclear clocks, by contrast, measure time using transitions between different nuclear energy levels.
Because an atomic nucleus is much smaller than an atom and nuclear transitions tend to be less sensitive to some external electromagnetic disturbances, nuclear clocks are expected to provide more precise and practical time and frequency standards than atomic clocks.
A research team led by Ding Shiqian, an associate professor in Tsinghua University’s Department of Physics, successfully developed the world’s first 148-nanometre continuous-wave vacuum-ultraviolet laser. This overcame a key challenge in producing a light source capable of precisely triggering energy-level transitions in the thorium-229 nucleus.
In collaboration with partners, the team also developed a calcium fluoride crystal doped with thorium-229 using just 1.4 micrograms of the isotope. The researchers said this had laid the core technological foundation for developing a nuclear clock.
“We have built a complete technological system covering the primary light source, the nuclear-clock crystal, the nuclear-transition spectrum and closed-loop operation,” Ding said.