@article{ec0a51d541454e4cae953563153a7520,
title = "Optical frequency ratio of a 171Yb+ single-ion clock and a 87Sr lattice clock",
abstract = "We report direct measurements of the frequency ratio of the 642 THz 2S1/2(F = 0)-2F7/2(F = 3) electric octupole transition in 171Yb+ and the 429 THz 1S0 -3P0 transition in 87Sr. A series of 107 measurements has been performed at the Physikalisch-Technische Bundesanstalt between December 2012 and October 2019. Long-term variations of the ratio are larger than expected from the individual measurement uncertainties of few 10−17. The cause of these variations remains unknown. Even taking these into account, we find a fractional uncertainty of the frequency ratio of 2.5 × 10−17, which improves upon previous knowledge by one order of magnitude. The average frequency ratio is νYb+ /νSr = 1.495 991 618 544 900 537(38). This represents one of the most accurate measurements between two different atomic species to date.",
keywords = "Frequency ratio, Optical clocks, Strontium lattice clock, Ytterbium ion clock",
author = "S. D{\"o}rscher and N. Huntemann and R. Schwarz and R. Lange and E. Benkler and B. Lipphardt and U. Sterr and E. Peik and C. Lisdat",
note = "Funding information: [ We thank T Legero, D Matei, and S H{\"a}fner for operating the Si-2 laser system, C Grebing for operating one of the optical frequency combs during the first few measurements, and N Lemke, S Falke, A Al-Masoudi, M Abdel Hafiz, and C Sanner for their contributions to operating the clocks during some measurements. We acknowledge support by the project 18SIB05 ROCIT, which has received funding from the EMPIR programme co-financed by the Participating States and from the European Union's Horizon 2020 Research and Innovation Programme, and by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany's Excellence Strategy-EXC-2123 QuantumFrontiers-390837967 and CRC 1227 DQ-mat within project B02. We thank T Legero, D Matei, and S H{\"a}fner for operating the Si-2 laser system, C Grebing for operating one of the optical frequency combs during the first few measurements, and N Lemke, S Falke, A Al-Masoudi, M Abdel Hafiz, and C Sanner for their contributions to operating the clocks during some measurements. We acknowledge support by the project 18SIB05 ROCIT, which has received funding from the EMPIR programme co-financed by the Participating States and from the European Union{\textquoteright}s Horizon 2020 Research and Innovation Programme, and by the Deutsche Forschungs-gemeinschaft (DFG, German Research Foundation) under Germany{\textquoteright}s Excellence Strategy—EXC-2123 QuantumFron-tiers—390837967and CRC 1227 DQ-mat within project B02",
year = "2021",
month = feb,
doi = "10.1088/1681-7575/abc86f",
language = "English",
volume = "58",
journal = "METROLOGIA",
issn = "0026-1394",
publisher = "IOP Publishing Ltd.",
number = "1",
}
