Nuclear clock: scalable quantum system for time

Laser and quantum sciences have fueled revolutionary developments in atomic, molecular, and fundamental physics. Quantum state engineering and many-body physics are preparing coherent quantum systems at increasingly large sizes, revolutionizing the performance of atomic clocks and metrology and promising new discovery opportunities. Quantum technology has brought many thousands of atoms to coherence times of minutes, it is now also knocking on the door of nuclear physics, heralded by the recent breakthrough of quantum-state-resolved laser spectroscopy of thorium-229 nuclear transition. Using a precision frequency comb in the vacuum-ultraviolet, we coherently excite the thorium nuclear clock transition and connect its frequency directly to today's most precise atomic clock. This unification of precision metrology and nuclear physics sparks new ideas for testing fundamental physics and promises nuclear-based clock with billions of nuclear absorbers.