Overview

• Researchers performed 38 simultaneous frequency ratio measurements among ten optical clocks in six countries, including four direct comparisons conducted for the first time.
• Custom optical fiber links achieved 100 times greater precision than satellite-based methods, though fiber connections were limited to France, Germany and Italy.
• The improved accuracy of optical clocks promises enhanced performance for GPS, power grid management and financial transaction synchronization.
• Optical clocks now exceed cesium standards by two orders of magnitude, losing or gaining less than one second over billions of years.
• Investigators identified remaining measurement uncertainties and plan further coordinated trials to match clock precision ahead of redefining the SI second.