Vienna, Beijing teams unveil world’s first nuclear clocks

Two research teams working separately in Vienna and Beijing have built the first two working nuclear clocks. Both use the isotope thorium-229, and both teams reported their results on Wednesday, Oct. 7, in papers in the journal Nature. Neither clock beats today's best atomic clocks yet. But researchers say the devices could become the most accurate timekeepers ever built and open a new way to test the laws of physics.reuters+1

A conventional atomic clock keeps time by tracking electrons jumping between energy levels. These new clocks instead use lasers to shift protons and neutrons between energy states inside the thorium-229 nucleus, which is held in calcium fluoride crystals. The name has nothing to do with nuclear power. The clocks don't use fission or fusion.reuters

Beijing's clock is more stable, Vienna's runs on its own

According to the South China Morning Post, early results suggest the clock built by the Tsinghua University team is about six times as stable as the Vienna clock. The Beijing team also showed that two crystals grown separately kept the same time, which suggests such clocks can be reproduced reliably. The team's preprint says frequencies measured with the two crystals agreed at the $$10^{-13}$$ level.scmp+1

The Vienna clock, built at TU Wien, keeps itself stable: the thorium nuclei control the laser's frequency, so it doesn't have to depend on a conventional atomic clock. It ran for more than 24 hours without anyone stepping in, and reached a precision of about $$10^{-15}$$. That works out to an error of roughly one second in 30 million years.phys

"The two teams worked independently and reached operating thorium-229 nuclear clocks at the same time, using different experimental approaches," Tsinghua physicist Shiqian Ding told Reuters. He said the result shows "the concept is robust".reuters

Still short of the record

The best atomic clocks today would gain or lose only about one second over billions of years. TU Wien's Thorsten Schumm said the technology is still "far from its target performance." He noted that the two clocks have complementary strengths: "the Vienna clock has slightly better thorium crystals… while the Beijing team has a stronger laser. So already by putting these components together, we can build a significantly better clock".reuters

Atomic nuclei are thousands of times smaller than whole atoms, so they react less to outside disturbances, including electric fields. Schumm told ABC News in Australia that his team envisions eventually building "a chip-scale device".english.elpais+2

A tool for physics

Possible uses include satellite navigation, data synchronization and surveying. Victor Flambaum, a physicist at the University of New South Wales who was not involved in the work, said the clocks could detect how gravity affects time precisely enough to help with mining exploration. The Vienna team used its clock to search for dark matter. It found none, but the clock performed as well as the best atomic clocks in that experiment.abc+1

"It gives access to a whole new physics universe," Schumm said.reuters