New Compact Atomic Clock Uses Cold Atoms to Boost Precision and Stability

Physicists have unveiled a new atomic clock that promises to boost precision. They've created a compact atomic clock design that relies on cold rubidium atoms instead of the usual hot atoms, a switch the promises improved precision and stability.

The heart of the prototype clock is about half the size of a coffee mug and is set in a small table of lasers and electronics. This new clock is about 10 times larger than NIST's chip-scale atomic clock packages. Yet researchers hope that when this clock is miniaturized and improved, it will have the potential to be about the same size and about 1,000 times more precise and stable than chip-scale atomic clocks over crucial timespans of a day or more.

"We're trying to push ultraportable clocks to higher performance levels," said Elizabeth Donley, one of the physicists, in a news release. "The aim is to make a clock that does not even need calibration."

Chip-scale atomic clocks keep time well enough for many applications requiring timing synchronization over short periods, such as GPS receivers. This clock precision, though, tends to drift over time spans beyond a few hours. This is due to the fact that the atoms are dispersed in high-pressure gases, which alter the atoms' resonant frequency depending on temperature. The new cold-atom clock, though, doesn't use these gases at all. This makes it far more precise since the source of error is essentially eliminated.

So how does it work? The cold-atom clock relies on about 1 million rubidium atoms held in a small glass vacuum chamber. The atoms are cooled with lasers and then trapped with magnetic fields at very cold temperatures. Two near-infrared lasers excite the atoms symmetrically from above and below. Each laser generates two frequencies of light, which are tuned until the atoms oscillate between two energy states and stop absorbing light. This sets the clock ticking rate at a specific microwave frequency.

Currently, the researchers are already working on the next version of the cold-atom clock. They plan to reduce its size and improve its performance by adding magnetic shield and antireflection coating. This clock has the potential to synchronize telecommunications networks and perform other exacting applications.

The findings are published in the journal Physical Review A.