Atomic clock could become accurate to within 40�ms over the age of the universe

Highly charged ions set to transform accuracy of atomic clock

New research in the atomic clock promises to be accurate to within 40 ms over the age of the universe, say physicists in the US and Australia.

A new atomic clock has been proposed by physicists in the US and Australia. The clock, based on a bismuth atom that has been stripped of 25 of its electrons, could be used to look for variations in the fine-structure constant – according to its designers. Experts claim this discovery could lead to a new unified theory of physics.

The best clocks of today use an atomic conversion as a time standard to measure time to an accuracy of about one part in 1017. Physicists are keen on building even better timepieces as they claim a clock with this heightened accuracy may help reveal minute changes in the world of physicists. They say it will help reveal the values of fundamental physical constants such as the fine-structure constant, a parameter that characterizes the strength of the electromagnetic interaction. Detecting possible variations that could help solve the biggest mystery of physics and give them insights into gravity, electromagnetism and the strong and weak nuclear forces.

As of March 2012, Corey Campbell’s team at the Georgia Institute of Technology argued that the required level of precision could be attained by using a particular nuclear transition in the thorium-229 ion with a charge of 3+. This remains a prediction as a practical clock is unlikely as problems remain in calculations and use of radioactive resources.

Three of Campbell's collaborators have proposed a solution using highly charged ions. Andrei Derevianko of the University of Nevada in Reno and Vladimir Dzuba and Victor Flambaum of the University of New South Wales in Sydney, having been looking at traditional atomic clocks in order to compare their properties to that of nuclear clocks.

The most accurate current atomic clocks of today use aluminium ions (Al+) in an electromagnetic trap. Yet problems of stray fields in the trap can disrupt the energy levels of the ion and reduce the clock’s performance.

The new clock is incredibly difficult to build but researchers remain adamant that a solution is possible. "It is much harder to trap and cool highly charged ions," explains Flambaum, "It is a new technique that has just started to appear. But people do this – it is not like our proposal just appeared out of the blue. It is just a new technology that requires new installations. It was much easier to work with neutral atoms or singly ionized atoms so of course people started from this, but now the time has come to search for other opportunities."

Atomic-clock expert, Helen Margolis, at the National Physical Laboratory in Teddington, is intrigued by the proposal. She believes that it poses many challenges before experiments can take place, stating: "People are very clever at dreaming up new ways to do things, but working on highly charged ions of this type is certainly not easy and they would need to do a lot of things that have never been done before."

Margolis does not share Derevianko's confidence that current calculations will produce reliable predictions:"It is true that for the highly charged ion clock the calculations of where these transitions occur are probably better but they are still not accurate enough to make the search for these transitions easy."

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