Single-atom optical clock with high accuracy

W. H. Oskay, S. A. Diddams, E. A. Donley, T. M. Fortier, T. P. Heavner, L. Hollberg, W. M. Itano, S. R. Jefferts, M. J. Delaney, K. Kim, F. Levi, T. E. Parker, J. C. Bergquist

Research output: Contribution to journalArticlepeer-review

276 Citations (Scopus)


For the past 50 years, atomic standards based on the frequency of the cesium ground-state hyperfine transition have been the most accurate time pieces in the world. We now report a comparison between the cesium fountain standard NIST-F1, which has been evaluated with an inaccuracy of about 4×10-16, and an optical frequency standard based on an ultraviolet transition in a single, laser-cooled mercury ion for which the fractional systematic frequency uncertainty was below 7.2×10-17. The absolute frequency of the transition was measured versus cesium to be 1064721609899144. 94 (97) Hz, with a statistically limited total fractional uncertainty of 9.1×10-16, the most accurate absolute measurement of an optical frequency to date.

Original languageEnglish
Article number020801
JournalPhysical review letters
Issue number2
Publication statusPublished - 2006

All Science Journal Classification (ASJC) codes

  • General Physics and Astronomy


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