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White papers

White paper

Cesium beam clocks: magnetic versus optical technology

Cesium beam clocks have long stood as the pinnacle of precision in timekeeping. These clocks, which have their foundation in the International System of Units (SI) definition of a second, rely on the oscillations between hyperfine levels of cesium 133 (133Cs) atoms. While earlier models utilized magnetic deflection, the advent of advanced lasers drives a transition to optical pumping methods. This shift significantly amplifies atomic flux and clock stability. Moreover, unlike closed magnetic designs, optical clocks’ critical laser components are air-exposed, facilitating easy maintenance and replacement.


However, optical clocks aren’t without challenges. They are sensitive to “light frequency shift,” which, if not properly managed, can impact their accuracy. Fortunately, advancements in proprietary algorithms promise to minimize this issue. When the performance of the two clocks was compared, optical clocks exhibited superior stability and accuracy. Their frequency stability reached the low 1E-15 range, and their time interval error was measured at ±10 ns for 60 days of operation, clearly showcasing their potential to revolutionize industries ranging from defense to finance.


As global industries rely more on precision timekeeping, the enhancement of cesium beam clocks is crucial. Our in-depth white paper, written by Dr. Patrick Berthoud, delves into this pivotal evolution in network synchronization. It compares classical magnetic methods with emerging optical technologies, exploring the inherent challenges each faces and the potential solutions on the horizon. Read more for a comprehensive understanding of how these developments will redefine precision in myriad applications, and the promising future that optical timekeeping holds.