Heidelberg 2015 – wissenschaftliches Programm
A 17.2: Vortrag
Dienstag, 24. März 2015, 14:45–15:00, P/H1
Absolute frequency measurement of the 87Sr lattice clock at PTB — Ali Al-Masoudi, •Sören Dörscher, Vladislav Gerginov, Stefan Weyers, Christian Grebing, Burghard Lipphardt, Sebastian Häfner, Uwe Sterr, and Christian Lisdat — Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig
Comparisons of optical clocks to microwave or other optical clocks are of great importance e.g. for the search for drifts of fundamental constants, and they also serve to ascertain the correctness and completeness of their error budgets. We report on a recent measurement of the absolute frequency of the 1S0–3P0 transition in 87Sr against a Cs fountain clock. The result is in excellent agreement with recent measurements in other laboratories as well as our own previous measurements. The preliminary fractional uncertainty of this measurement is 4 × 10−16, to which the statistical uncertainty due to the measurement time of 267000 s still contributes considerably. However, this uncertainty can be reduced to below the systematic uncertainty of the Cs clock by an extension of the effective total measurement time through interpolation, which is currently under investigation. Finally, we present recent improvements of the lattice clocks at PTB for this measurement and towards a direct comparison of two separate 87Sr clocks. This work is supported by QUEST, the DFG within CRC 1128 (geo-Q) and RTG 1729, and the EMRP within IND14, ITOC, and QESOCAS. The EMRP is jointly funded by the EMRP-participating countries within EURAMET and the European Union.