Reacción a "The first thorium-229-based nuclear clocks are unveiled"

In general, nuclear clocks (thorium in particular) are currently regarded as the next step beyond existing optical atomic clocks.

At present, there are not many research groups working on this type of clock; I know that the US National Institute of Standards and Technology (NIST) is also working on them. The advantages they offer over current clocks are not only that they can achieve greater accuracy (beyond 10^-19), but also that they offer other benefits, such as reduced sensitivity to the environment and to electric fields. This greater accuracy will enable research into fundamental physics, such as investigating the accuracy of fundamental constants or dark energy.

But there is still a long way to go before we get there; these studies represent two further steps towards achieving the necessary stability and repeatability, so that these clocks can be compared with one another and with current ones, and can be used to define the second. Both studies focus on the same thorium isotope and aim to demonstrate that the nuclear transition is sufficiently reproducible to serve as a good oscillator. Their aim is to validate a robust platform for these to become clocks (the prerequisite being that they are good, reproducible and repeatable oscillators). In the Chinese study, the clock is about six times more stable in the short term than that in the Austrian study, but the strength of the Austrian study lies in the fact that it compares its results with a Yb [ytterbium] clock.

Both studies are aimed at improving the configuration of Th clocks and are significant in the context of future developments. Although it is unlikely that this type of clock will have a real impact on the new definition of the second (particularly if it is redefined in 2030; if it were postponed, they might stand a chance), they will undoubtedly play an important role in the medium term in future revisions or updates.