Researchers from the University of Adelaide have partnered with the US National Institute of Standards and Technology (NIST) and the UK’s National Physical Laboratory to assess the readiness of next-generation timekeeping technology. Their review concludes that optical atomic clocks have advanced so rapidly that they could redefine the international definition of the second within the next few years, provided remaining technical challenges are addressed.
Optical atomic clocks have seen dramatic improvements over the past decade, surpassing the accuracy of the best microwave atomic clocks currently used to define international time. Unlike traditional systems, some optical clocks are now capable of operating outside laboratory environments, opening new possibilities for real-world applications.
The clocks work by trapping atoms or ions and cooling them with lasers. When probed repeatedly, the atoms respond at an extremely precise frequency, which can be converted into highly accurate time “ticks”. This precision makes optical atomic clocks some of the most accurate measurement devices ever built.
The review, published in the journal Optica, outlines progress made over the past ten years, identifies technical and operational challenges, and explores future applications. According to the researchers, optical atomic clocks have already begun influencing international timekeeping, with at least ten systems now approved for use in steering global time standards.
Beyond redefining the second, optical atomic clocks could support a range of new capabilities. Their sensitivity allows them to act as gravity sensors, potentially enabling a global height reference system that does not rely on sea level. They may also be used to test fundamental physics, including searches for dark matter.
The technology could also improve resilience in space-based systems, helping maintain accurate time during satellite outages caused by solar storms or hostile interference. This potential has attracted growing commercial interest, including from Adelaide-based spin-out company QuantX Labs.
Despite the progress, challenges remain. Many optical atomic clocks still operate intermittently, and decisions are required on how best to redefine the second, including whether a single clock type or a combination of systems should replace existing caesium fountain clocks. Direct comparisons between different optical clocks will be critical.
Supply chains for key components are also immature, contributing to high costs. However, researchers expect advances in related fields such as quantum computing and biosciences to drive greater affordability and accessibility over time.
The research was supported by NIST’s Physical Measurement Laboratory, Australia’s Defence Science and Technology Group, and the Australian Research Council Centre of Excellence in Optical Microcombs for Breakthrough Science.
