A Thorium-229 nuclear clock

Abstract: 

Optical atomic clocks are used for precise time/frequency measurements and provide deep insights to fundamental physics. Enabled by a frequency comb in the vacuum-ultraviolet (VUV), we perform precision spectroscopy of the thorium-229 nuclear transition in a solid-state crystalline host. We resolve the individual nuclear quantum states and characterize state-dependent systematic clock frequency shifts with respect to temperature and doping concentration. This nuclear clock promises a portable solid-state platform with high stability and reproducibility, and intrinsic sensitivity enhancement for beyond-standard-model physics.