Demonstration of a Mobile Optical Clock Ensemble at Sea

Atomic clocks are at the leading edge of accuracy and precision and are essential for synchronization of distributed critical infrastructure, position, navigation and timing, and scientific applications. There has been a breakthrough in the performance of atomic clocks with the shift from microwave to optical frequency transitions. However, this performance increase has come at the cost of size, complexity and fragility, which has confined optical clocks to laboratories. Here we report on a recent international collaboration where three emerging optical clocks, each based on different operating principles, were trialled at sea. Over weeks of unsupervised naval operation, these clocks demonstrated exceptional reliability and provided frequency stability outputs in optical, microwave and radio-frequency domains. The performance of all three devices was orders of magnitude superior to existing best-in-class commercial solutions over short and medium timescales, marking a significant step toward deploying optical clocks in real-world environments.