Precision time-keeping is moving on from atomic clocks and embracing the revolution that is optical atomic clocks. Over the last few years, these instruments have gone further and further in the precision timekeeping they can demonstrate. Their level now is outstanding, well beyond the capabilities of regular atomic clocks.
Atomic clocks use cesium atoms cooled to a temperature near absolute zero. By measuring the resonant frequency of these atoms, it can keep a beat. The most advanced atomic clocks do not lose more than a second in 300 million years. However, scientists realized it is possible to do better – using a “web of light”, or technically an optical lattice, it is possible to trap and measure tens of thousands of atoms.
The lattice in this case holds 40,000 strontium atoms at just a fraction of a degree above absolute zero. The ticking of this clock is a transition between specific energy levels for the electrons in this atom. Using this, researchers were able to measure time with an uncertainty of 8.1 parts per tenth of a billionth of a billionth.
You might wonder why it is useful to have such high precision. Aren’t atomic clocks precise enough for humanity? The answer is yes and no. Atomic clocks’ astounding precision has helped in many different aspects of our lives. One that is used often is GPS: Having optical clocks take their place would push accuracy to at least 1,000 times higher. But it will also open new ways to test fundamental physics.
“There will be very interesting discoveries that are waiting for us if we get to the times that are sensitive to the very small space-time curvature,” senior author Professor Jun Ye told IFLScience when it was announced he had won the 2022 Breakthrough Prize in Fundamental Physics.
One of the possibilities is using these clocks to study general relativity. Atomic clocks, especially on GPS satellites, experience that already – but the boost in precision allows us to check if our assumptions are correct to a more stringent level, and maybe see things we have not seen before.
“We’re exploring the frontiers of measurement science,” Ye said in a statement. “When you can measure things with this level of precision, you start to see phenomena that we’ve only been able to theorize about until now.”
“This clock is so precise that it can detect tiny effects predicted by theories such as general relativity, even at the microscopic scale. It’s pushing the boundaries of what’s possible with timekeeping.”
The precision might not feel revolutionary in the map app of your phone, but as humanity continues to explore the solar system it will make a lot of difference. It might just open the door for breakthroughs in quantum computing.
“If we want to land a spacecraft on Mars with pinpoint accuracy, we’re going to need clocks that are orders of magnitude more precise than what we have today in GPS,” added Ye, who’s from the National Institute of Standard and Technology and the University of Colorado Boulder. “This new clock is a major step towards making that possible.”
A paper describing the results will be published next week in Physical Review Letters.
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