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The optical calcium frequency standards of PTB and NIST
Published
Author(s)
U Sterr, C Degenhardt, H Stoehr, Ch. Lisdat, H Schnatz, J Helmcke, F Riehle, G Wilpers, Christopher W. Oates, Leo W. Hollberg
Abstract
We describe the current status of the optical calcium frequency standard with laser-cooled neutral atoms realized in two different laboratories for the purpose of developing a possible future optical atomic clock. Frequency measurements performed at PTB and NIST make the frequency of the clock transition of 40}Ca one of the best known optical frequencies (relative uncertainty 1.2 x 10u-14}) and agree in both laboratories to well within their respective uncertainties. Prospects for orders of magnitude improvement in the standard look feasible.
Sterr, U.
, Degenhardt, C.
, Stoehr, H.
, Lisdat, C.
, Schnatz, H.
, Helmcke, J.
, Riehle, F.
, Wilpers, G.
, Oates, C.
and Hollberg, L.
(2004),
The optical calcium frequency standards of PTB and NIST, Comptes Rendus Mathematique, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=50037
(Accessed October 23, 2025)