Frequency reproducibility of solid-state thorium-229 nuclear clocks

Solid-state thorium-229 (229Th) nuclear clocks1–5 are set to provide new opportunities for precision metrology and fundamental physics6–8. Taking advantage of inherent low sensitivity of a nuclear transition to its environment9, orders of magnitude more emitters can be hosted in a solid-state crystal compared with current optical lattice atomic clocks10. Furthermore, solid-state systems needing only simple thermal control11 are key to the development of field-deployable compact clocks.