Cool technology for time-keeping

Timekeeping just gets better and better. A joint project by Physikalisch-Technische Bundesanstalt (Physical and Technical Institute of Germany) and the National Physical Laboratory has resulted in a brand new timekeeping technology. From the National Physical Laboratory:

The tick-tock of the optical clock
NPL time scientists have made an accurate measurement of the highly forbidden octupole transition frequency in an ytterbium ion, which could be used as the basis for the next generation of optical atomic clocks.

Ytterbium (Yb) is a metallic element that could be used in ultra-high accuracy optical clocks. Atomic clocks that use the microwave frequency of caesium atoms are currently the gold standard when it comes to timekeeping, with NPL's caesium fountain clock being the UK's primary standard and currently the most accurate system of its kind in the world. But clocks that rely on optical frequencies, such as those based on that of ytterbium, have the potential to surpass microwave atomic clocks, with up to 100 times better stability and accuracy.

In research at NPL, published in the New Journal of Physics [1], a measurement of the frequency of a transition of an ytterbium ion, known as an octupole transition, is presented with a level of uncertainty of one part in 1015. This represents an improvement by a factor of 20 on the previous measurement and agrees with a similar measurement [2] made by the German National Measurement Institute, PTB, and published soon after the NPL paper, with an uncertainty of 0.8 parts in 1015. In fact, the results demonstrate the best international agreement between trapped ion optical frequency standards to date.

From the Physikalisch-Technische Bundesanstalt:

New "pendulum" for the ytterbium clock
The faster a clock ticks, the more precise it can be. Due to the fact that lightwaves vibrate faster than microwaves, optical clocks can be more precise than the caesium atomic clocks which presently determine time. The Physikalisch-Technische Bundesanstalt (PTB) is even working on several of such optical clocks simultaneously. The model with one single ytterbium ion caught in an ion trap is now experiencing another increase in accuracy. At PTB, scientists have succeeded in exciting a quantum-mechanically strongly "forbidden" transition of this ion and - in particular - in measuring it with extreme accuracy. The optical clock based on it is exact to 17 digits after the decimal point. The results are published in the current edition of the scientific journal "Physical Review Letters".

To grasp the enormity of this advance here is one line from the PTB article:

This corresponds to an uncertainty of the atomic clock of only approx. 30 seconds over the age of the universe.

Just wow!