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Alpha-Dot or Not: Comparison of Two Single Atom Optical Clocks



Till P. Rosenband, David Hume, Chin-Wen Chou, J.C. Koelemeij, A. Brusch, Sarah Bickman, Windell Oskay, Tara M. Fortier, Jason Stalnaker, Scott A. Diddams, Nathan R. Newbury, William C. Swann, Wayne M. Itano, David J. Wineland, James C. Bergquist


Repeated measurements of the frequency ratio of Hg+ and Al+ single-atom optical clocks over the course of a year yield a constraint on the possible temporal variation of the fine-structure constant a. The time variation of the measured ratio corresponds to a time variation in the fine structure constant of α-dot/α=(-1.6 ± 2.3) × 10-17, which is consistent with no change. The frequency ratio of these clocks was measured with a fractional uncertainty of 5.2 × 10-17. Stability simulations for optical clocks whose probe time is limited by 1/f-noise in the laser local oscillator yield an estimate of the optimal probe time, as well as a modified expression for the theoretical clock stability.
Proceedings Title
Proc. 2008 Symposium on Frequency Standards and Metrology
Conference Dates
October 5-11, 2008
Conference Location
Pacific Grove, CA


optical clocks, atomic clocks, trapped ions


Rosenband, T. , Hume, D. , Chou, C. , Koelemeij, J. , Brusch, A. , Bickman, S. , Oskay, W. , Fortier, T. , Stalnaker, J. , Diddams, S. , Newbury, N. , Swann, W. , Itano, W. , Wineland, D. and Bergquist, J. (2008), Alpha-Dot or Not: Comparison of Two Single Atom Optical Clocks, Proc. 2008 Symposium on Frequency Standards and Metrology, Pacific Grove, CA, [online], (Accessed April 23, 2024)
Created October 5, 2008, Updated February 19, 2017