The world keeps time with the ticks of atomic clocks, but a new type of clock under development—a nuclear clock—could revolutionize how we measure time and probe fundamental physics.

An international research team led by scientists at the Joint Institute for Laboratory Astrophysics (JILA), a collaboration of the National Institute of Standards and Technology (NIST) and the University of Colorado-Boulder, has demonstrated key elements of a nuclear clock. It’s a novel timekeeping device that would use signals from the core, or nucleus, of an atom. The team used a specially designed ultraviolet laser to precisely measure the frequency of an energy jump in thorium nuclei embedded in a solid crystal. The team also employed an optical frequency comb, which acts like an extremely accurate light ruler to count the number of ultraviolet wave cycles that create this energy jump. Although this laboratory demonstration isn’t a fully developed nuclear clock, it contains all the key technology for one.

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