Time isn’t exactly speeding up, but thanks to atomic physicists, the accuracy of timekeeping has markedly improved. Reliance on atomic clocks to support international time documentation, particle physics research and other applications may be superseded by the evolution of a nuclear clock by an international research team.

While atomic clocks gauge time by tuning laser light to frequencies that cause electrons to jump between energy levels, the nuclear clock technology is based on signals from the nucleus of an atom. Researchers applied a specially designed ultraviolet laser to precisely measure the frequency of an energy jump in thorium nuclei embedded in a solid crystal. An optical frequency comb was also deployed to count the number of ultraviolet wave cycles that create this energy jump. The laser light used to induce energy jumps in nuclei is much higher in frequency than that required for atomic clocks and leads to more precise timekeeping.

The research reported in Nature documented a level of precision that is one million times higher than the previous wavelength-based measurement. In addition, they compared this ultraviolet frequency directly to the optical frequency used in one of the world's most accurate atomic clocks, which uses strontium atoms, establishing the first direct frequency link between a nuclear transition and an atomic clock. This direct frequency link and increase in precision are crucial steps in developing the nuclear clock and integrating it with existing timekeeping systems.

The precision of the nuclear clock is predicted to surpass that of atomic clocks in two to three years, and should also be more portable and stable.

Researchers from the University of Colorado Boulder, École Polytechnique Fédérale de Lausanne (Switzerland), TU Wien (Austria), IMRA America, Ludwig-Maximilians-Universität München (Germany) and the U.S. National Institute of Standards and Technology contributed to this chronological development.