USA builds world’s most accurate atomic clock ever

Researchers at JILA, an American research institute, have developed a new light-based atomic clock that is so precise it can measure the smallest effects, as predicted by Einstein’s theory of general relativity. The clock will lead to a more precise determination of a second and may even lead to the discovery of new underground mineral deposits, said a press release from the organization.

Atomic clocks usually use microwaves to measure the length of a second. However, research has shown that illuminating atoms with visible light can help count the second much more accurately since the light waves have a higher frequency.

Light-based or optical atomic clocks can lose one second every 30 billion years compared to microwave-based clocks. However, to achieve this accuracy, the clocks must be of high precision, ie able to measure small fractions of a second.

Quantum computer
Representative image of a quantum computer using atomic manipulation to perform complex calculations. Image credit: Peter Hansen/ iStock

Improving the accuracy of the atomic clock

Instead of using a beam of visible light, researchers at JILA used a grating of light, also known as an optical grating, to measure tens of thousands of atoms simultaneously. This gave the atomic clock more data to arrive at an accurate measurement of the second.

Although the optical lattice approach has been used before, the JILA researchers used a relatively gentler approach to make their measurements. This helped reduce two sources of error: the laser itself measuring the atoms and the effect of atoms bumping into each other when they are packed tightly together, the press release said.

Measuring the effects of relativity and beyond

According to Einstein’s theory of general relativity, gravity affects time. A stronger gravitational field results in a slower passage of time. The watch developed by JILA is sensitive enough to detect the effect of gravity on time measurement on a submillimetre scale.

The researchers observed subtle changes in the flow of time due to gravity, when the clock rose or fell even over small distances.

“It’s pushing the limits of what’s possible with time measurement,” said Jun Ye, a physicist at JILA and NIST. However, the benefits of clock design go beyond these measurements and into the quantum realm.

Quantum computers manipulate the properties of atoms and molecules to perform complex calculations. Since the JILA clock can make precise measurements, the researchers plan to use it in the microscopic realm, where the theories of general relativity and quantum mechanics intersect, to measure distortions in the flow of time on scales distorted by gravity.

At the same time, the precision of the clock can help scientists keep accurate time across extremely large distances in space. “If we want to land a spacecraft on Mars with pinpoint accuracy, we will need clocks that are orders of magnitude more accurate than what we have today in GPS,” Ye added in the press release.

“We’re exploring the frontiers of measurement science, 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,” Ye concluded.

JILA is a joint institute between the National Institute of Standards and Technology (NIST) and the University of Colorado Boulder.

The research findings will be published in the journal Physical review papers.


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Ameya Paleja Ameya is a science writer based in Hyderabad, India. A molecular biologist at heart, he traded in the micropipette to write about science during the pandemic, and he doesn’t want to go back. He enjoys writing about genetics, microbes, technology and public policy.

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