China builds super-accurate optical clock

Chinese scientists say they have assembled the country's first optical clock, capable of measuring time more precisely than traditional atomic timekeepers. Researchers at the Hubei Academy of Sciences in central China said the clock, based on a single calcium ion, could remain accurate within 1 second for more than 10 million years. Electric and magnetic fields are used to "trap" a calcium ion, allowing researchers to pinpoint the passage of time by tracking the ion's atomic movement, academy researcher Gao Kelin said. "Unlike microwave clocks, which track atomic movement in the microwave range, optical clocks observe the optical range, which can reduce uncertainty by 100 to 1,000 times," Gao told China's state-run Xinhua News Agency. China is the seventh country in the world to create an optical clock, following the United States, Germany, Britain, Canada, Austria and Japan.