Only hot atoms were ever used in such devices before

Nov 6, 2013 07:43 GMT  ·  By
NIST physicist Elizabeth Donley with a compact atomic clock design that could help improve precision in ultraportable clocks
   NIST physicist Elizabeth Donley with a compact atomic clock design that could help improve precision in ultraportable clocks

In a study that could lead to significant improvements in the precision and stability of atomic clocks, researchers at the US National Institutes of Standards and Technology (NIST) were able to create an atomic clock that is not based on the usual, hot atoms, but rather on cold rubidium atoms. 

Since the device is currently a proof-of-concept, its heart is currently about 150 cubic centimeters in volume, roughly the volume of small coffee mug. Surrounded by electronics and lasers, this vacuum chamber is the container holding the cold atoms. This device is now 10 times larger than chip-scale atomic clocks currently in use.

However, the team says that they have not yet started the miniaturization and optimization process. NIST physicists are hopeful that, once this is done, the instrument will be of equal-size to a chip-scale atomic clock, but up to 1,000 times more precise and stable over the course of a day.

Details of the study appear in a paper entitled “A cold-atom double-lambda CPT clock,” which is published in the October 31 issue of the top scientific journal Physical Review. The work suggests that cold rubidium atom clocks may soon replace the common cesium-beam atomic clocks.

One of the reasons the new clock does not feature the same errors as its predecessors is that it dispenses with the high-pressure gases that are required to keep hot-atom clocks operating. In these devices, temperature fluctuations can change the resonant frequencies of the atoms, leading to flaws.

By using cold atoms and renouncing the gases altogether, the new, small, low-power clocks could become much more desirable for applications requiring accurate time-keeping over short periods, ranging from several hours to several days.

“We're trying to push ultraportable clocks to higher performance levels. The aim is to make a clock that does not even need calibration,” explains team member Elizabeth Donley, a NIST physicist.

Unlike their hot-atom counterparts, the new atomic clocks are based on a chamber containing around 1 million rubidium atoms, which are cooled to temperatures reaching 0 Kelvin by a matrix of lasers and magnetic fields.

The NIST team now plans to further improve on their design by adding magnetic shielding and antireflection coating to the clocks, while also striving to miniaturize them further.