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.
Proc. 2008 Symposium on Frequency Standards and Metrology