Trapped-ion optical clocks

Article By:

Klein, Hugh National Physical Laboratory, United Kingdom.

Last reviewed:2006

DOI:https://doi.org/10.1036/1097-8542.YB060570

Increasingly stringent demands on atomic timekeeping, driven by applications such as global navigation satellite systems (GNSS), communications, and very long baseline interferometry (VBLI) radio astronomy, motivate the development of improved time and frequency standards. This article discusses frequency standards and clocks based on optical transitions in trapped, singly ionized atomic systems. The year 2005 marked the fiftieth anniversary of the first working cesium atomic clock. Cesium microwave frequency standards have since improved in accuracy by an order of magnitude per decade. Today the best primary standards can realize the second, as defined in the International System of Units (SI), with an accuracy of better than 1 part in 10¹⁵. However, this is near the limit to which a standard based on the cesium hyperfine transition can be developed. Standards based on optical transitions are anticipated to reach two or more orders of magnitude greater accuracy and stability. It is widely expected that the development of such optical clocks will lead to the redefinition of the SI second in terms of an optical transition in place of the cesium hyperfine transition.

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