Researchers in China have developed an optical atomic clock with accuracy high enough to potentially contribute to redefining the international standard for measuring time. The device is capable of losing or gaining less than one second over a period of roughly 30 billion years, making it one of the most precise timekeeping systems ever created.
The clock was built by scientists at the University of Science and Technology of China and represents a significant advancement in optical timekeeping technology. Optical clocks use the frequency of light emitted when electrons transition between energy levels inside atoms to measure time with extremely high precision, according to the SCMP.
Unlike traditional atomic clocks that rely on microwave frequencies from cesium atoms, optical clocks operate at much higher frequencies within the optical spectrum. Because these frequencies oscillate faster, they allow time intervals to be divided into smaller units, improving measurement resolution.
The newly developed system is based on a strontium optical lattice design, in which thousands of strontium atoms are trapped within a lattice formed by laser beams. This configuration stabilizes the atoms and allows researchers to measure the optical transition frequency with extremely low uncertainty.
Optical clocks can measure time to nearly nineteen decimal places, placing them among the most precise scientific instruments currently available. Researchers report that the new clock surpasses the previously difficult threshold of 10?¹? fractional frequency uncertainty, meaning its error accumulation is extremely small even over very long timescales.
Such precision could influence the definition of the second, the fundamental unit of time in the International System of Units. Historically, the second was defined as one eighty six thousand four hundredth of a day based on Earth’s rotation. However, variations in the planet’s rotation made that definition insufficient for precise scientific measurement.
In 1967, the international standard was updated so that one second equals 9,192,631,770 oscillations of radiation associated with a transition in the cesium 133 atom. Cesium atomic clocks have served as the global reference for timekeeping ever since.
Optical clocks may now provide a more accurate alternative. Because they operate at higher frequencies and achieve lower measurement uncertainty, scientists believe they could form the basis of a future redefinition of the second.
The study describing the new device was published in the journal Metrologia. Researchers say the clock meets one of the technical performance thresholds required for redefining the SI second.
In order for the international time standard to be updated, multiple independent laboratories must demonstrate optical clocks with similar levels of stability and accuracy. Current guidelines require at least three such systems at different institutions before a redefinition can be considered.
Beyond timekeeping, ultra precise clocks have important applications in scientific research and engineering. Small differences in time measurement can be used to detect variations in gravitational fields, allowing scientists to measure altitude differences as small as a few millimeters.
Researchers also use high precision clocks to study fundamental physical phenomena including gravitational waves, shifts in Earth’s crust, and potential signals related to dark matter interactions.
As more laboratories achieve similar levels of performance, optical clock networks may eventually replace cesium based systems as the primary reference for global time measurement.
