Smaller version Illustration of a conventional atomic fountain clock (left) next to NPL’s miniature atomic fountain clock. (Courtesy: NPL)"> Smaller version Illustration of a conventional atomic fountain clock (left) next to NPL’s miniature atomic fountain clock. (Courtesy: NPL)

A miniature version of an atomic fountain clock has been unveiled by researchers at the UK’s National Physical Laboratory (NPL). Their timekeeper occupies just 5% of the volume of a conventional atomic fountain clock while delivering a time signal with a stability that is on par with a full-sized system. The team is now honing its design to create compact fountain clocks that could be used in portable systems and remote locations.

The ticking of an atomic clock is defined by the frequency of the electromagnetic radiation that is absorbed and emitted by a specific transition between atomic energy levels. Today, the second is defined using a transition in caesium atoms that involves microwave radiation.…