Atomic clocks are recorded using microwaves at frequencies that match the electron transitions of a particular atom. They are the basis for the second one being defined. But Brock has a new child. This boasts even higher accuracy. Is it time to redefine the second?
The optical clock can reach accuracy at 10 levels-18 “This is such a precise number that if a watch starts running in the Big Bang, it’s now lost in just a second,” says Alexandra Tofful, an optical clock physicist at the National Institute of Physics (NPL), London, who oversees UK scientific metrics.
Unlike atomic clocks, this new type of timekeeper probes electronic transitions with light. “Visible light has five orders of magnitude higher frequencies than microwaves, so the optical clock is about 100 times more accurate than today’s cesium atomic clock,” says Tofful. In NPL, the optical clock she is working on is a single ytterbium ion trapped in its core. This is particularly sensitive to variations in fine structural constants, which are measures of the strength of electromagnetic interparticles. “It’s the perfect optical clock to use in basic physics testing,” says Tofful. For example, there is a suggestion that fundamental constants may not actually be constant, explained Tofful. The optical clock can achieve a level of accuracy that can detect these changes.
On a more practical level, it uses precise time to synchronize many of the infrastructure it relies on, from banks to transportation to energy networks. At NPL, researchers not only develop optical clocks to measure time more accurately, but also build a network of clocks that add resilience to timekeepers that support critical infrastructure. “[Time] signals that are being broadcast are being targeted for disruption or denial,” says Leon Lobo, head of the National Timing Centre programme at NPL. In the worst-case scenarios, these signals can be hijacked, and the timing can be changed. This has been especially noticeable in conflict zones such as Ukraine, Russia and the Middle East. To this end, NPL is developing a series of optical clocks that are geographically distributed around the UK, But it is connected through various time transfer methods.
