Skip to main content
Metrology

Metrology

Atomic clocks speed up

03 Oct 2001

Accurate clocks contribute to science, technology and trade to an extent that can hardly be overestimated. Now a device called a frequency comb has led to the creation of the world’s most accurate atomic clock.

The most successful applications of atomic clocks include the global positioning system (GPS) of satellites for navigation, and also the international basis of timekeeping, known as the coordinated universal timescale or UTC. Atomic clocks are also used in precision tests of fundamental theories, such as quantum electrodynamics and general relativity.

Historically the increase in accuracy of clocks has involved long periods of continuous development that are interrupted by sudden improvements due to new technologies or systems. These leaps in accuracy are often associated with an increase in the frequency of the oscillator that sits at the heart of any clock. Such a revolution occurred in about 1930 when pendulum clocks with frequencies of a few hertz were replaced by quartz oscillators with frequencies in the megahertz range. A similar jump occurred with the advent of atomic clocks based on microwave transitions in the gigahertz range.

Now it seems that time metrology is about to undergo another giant leap in frequency thanks to the development of atomic clocks that use optical transitions, rather than microwave ones. Scott Diddams and co-workers at the National Institute of Standards and Technology (NIST) in Boulder, Colorado, have demonstrated an optical atomic clock based on a petahertz (1015 Hz) transition of a single mercury-199 ion (S Diddams et al. 2001 Science 293 825).

In the October issue of Physics World, Fritz Riehle of the Physikalisch Technische Bundesanstalt, Braunschweig, Germany, descibes how the super-accurate clock works.

Related events

Copyright © 2024 by IOP Publishing Ltd and individual contributors