Overview
- In early June, two independent teams reported functioning nuclear-clock prototypes that close the missing feedback loop by locking an ultraviolet laser to a thorium-229 nuclear transition.
- Both prototypes embed thorium-229 ions in calcium fluoride crystals and use an active measurement-and-correction routine that nudges the laser frequency until it matches the nuclear resonance.
- The clocks are demonstrably running but do not yet beat the best atomic (electron-based) clocks in stability, with current performance corresponding to losing tens of seconds per billion years.
- Because nuclear transitions sit inside the nucleus they are far less affected by stray electromagnetic fields and can operate in solid, room-temperature devices, and the teams already used the clocks to search for ultralight dark matter with no detection but competitive sensitivity.
- Results are presented as arXiv preprints and await peer review, and researchers say targeted improvements in lasers, crystal quality and thorium concentration could rapidly raise stability and enable miniaturized, space-capable timekeepers and new precision tests of fundamental constants.