The 229Th nuclear clock, based on a low-energy nuclear transition, has attracted significant interest as a next-generation time and frequency standard. It is expected to surpass current leading optical atomic clocks in performance. Because nuclear transitions are naturally isolated from external electromagnetic fields, their sensitivity to blackbody radiation and environmental noise is much lower than that of electronic transitions. This gives the nuclear clock a unique advantage in both stability and accuracy. This paper reviews the current progress in nuclear clock research, focusing on the physical properties of the 229Th isomer, the operating principles, and the primary implementation methods of the nuclear clock. Comparing key technical approaches, specifically trapped ions and thorium-doped crystals, and introducing the VUV frequency comb technology used to drive the nuclear transition. Finally, we provide an outlook on the future development of the field.
Luo et al. (Sat,) studied this question.