Highly charged ions: Optical clocks and applications in fundamental physics

authored by: Mikhail G. Kozlov, Marianna S. Safronova, José R. Crespo López-Urrutia, Piet Oliver Schmidt
Abstract: Recent developments in frequency metrology and optical clocks have been based on electronic transitions in atoms and singly charged ions as references. The control over all relevant degrees of freedom in these atoms has enabled relative frequency uncertainties at a level of 10-18. This accomplishment not only allows for extremely accurate time and frequency measurements, but also to probe our understanding of fundamental physics, such as a possible variation of fundamental constants, a violation of the local Lorentz invariance, and the existence of forces beyond the standard model of physics. In addition, novel clocks are driving the development of sophisticated technical applications. Crucial for applications of clocks in fundamental physics are a high sensitivity to effects beyond the standard model and a small frequency uncertainty of the clock. Highly charged ions offer both. They possess optical transitions which can be extremely narrow and less sensitive to external perturbations compared to current atomic clock species. The large selection of highly charged ions offers narrow transitions that are among the most sensitive ones for the "new physics" effects. Recent experimental advances in trapping and sympathetic cooling of highly charged ions will in the future enable advanced quantum logic techniques for controlling motional and internal degrees of freedom and thus enable high-accuracy optical spectroscopy. Theoretical progress in calculating the properties of selected highly charged ions has allowed the evaluation of systematic shifts and the prediction of the sensitivity to the physics beyond the standard model. New theoretical challenges and opportunities emerge from relativistic, quantum electrodynamics, and nuclear-size contributions that become comparable with interelectronic correlations. This article reviews the current status of the field, addresses specific electronic configurations and systems which show the most promising properties for research, their potential limitations, and the techniques for their study.
Organisation(s): Institute of Quantum Optics
CRC 1227 Designed Quantum States of Matter (DQ-mat)
External Organisation(s): Russian Research Centre Kurchatov Institute
St. Petersburg State Electrotechnical University
University of Delaware
University of Maryland
Max Planck Institute for Nuclear Physics
National Metrology Institute of Germany (PTB)
Type: Article
Journal: Reviews of Modern Physics
Volume: 90
ISSN: 0034-6861
Publication date: 04.12.2018
Publication status: Published
Peer reviewed: Yes
ASJC Scopus subject areas: Physics and Astronomy(all)
Electronic version(s): https://arxiv.org/abs/1803.06532 (Access: Open)
https://link.aps.org/accepted/10.1103/RevModPhys.90.045005 (Access: Open)
https://doi.org/10.1103/RevModPhys.90.045005 (Access: Closed)

BibTeX

@article{256e912b8a2b4e93bbf19113786012c2,
title = "Highly charged ions: Optical clocks and applications in fundamental physics",
abstract = "Recent developments in frequency metrology and optical clocks have been based on electronic transitions in atoms and singly charged ions as references. The control over all relevant degrees of freedom in these atoms has enabled relative frequency uncertainties at a level of 10-18. This accomplishment not only allows for extremely accurate time and frequency measurements, but also to probe our understanding of fundamental physics, such as a possible variation of fundamental constants, a violation of the local Lorentz invariance, and the existence of forces beyond the standard model of physics. In addition, novel clocks are driving the development of sophisticated technical applications. Crucial for applications of clocks in fundamental physics are a high sensitivity to effects beyond the standard model and a small frequency uncertainty of the clock. Highly charged ions offer both. They possess optical transitions which can be extremely narrow and less sensitive to external perturbations compared to current atomic clock species. The large selection of highly charged ions offers narrow transitions that are among the most sensitive ones for the {"}new physics{"} effects. Recent experimental advances in trapping and sympathetic cooling of highly charged ions will in the future enable advanced quantum logic techniques for controlling motional and internal degrees of freedom and thus enable high-accuracy optical spectroscopy. Theoretical progress in calculating the properties of selected highly charged ions has allowed the evaluation of systematic shifts and the prediction of the sensitivity to the physics beyond the standard model. New theoretical challenges and opportunities emerge from relativistic, quantum electrodynamics, and nuclear-size contributions that become comparable with interelectronic correlations. This article reviews the current status of the field, addresses specific electronic configurations and systems which show the most promising properties for research, their potential limitations, and the techniques for their study.",
author = "Kozlov, {Mikhail G.} and Safronova, {Marianna S.} and {Crespo L{\'o}pez-Urrutia}, {Jos{\'e} R.} and Schmidt, {Piet Oliver}",
note = "Funding information: We thank Steven King, Peter Micke, Andrei Nefiodov, Natalia Oreshkina, Sergey Porsev, and John Webb for helpful comments on the manuscript. M. G. K. acknowledges support from the Russian Foundation for Basic Research under Grant No. 17-02-00216. M. S. S. acknowledges support of the Office of Naval Research, USA, under Award No. N00014-17-1-2252. J. R. C. L.-U. acknowledges support by the DFG Collaborative Research Centre SFB 1225 (ISOQUANT). P. O. S. acknowledges support from PTB and DFG through SCHM2678/5-1 and the Collaborative Research Centre (Sonderforschungsbereich) SFB 1227 DQ- mat , project B03. This project has received funding from the European Metrology Programme for Innovation and Research (EMPIR) co-financed by the Participating States and from the European Union{\textquoteright}s Horizon 2020 research and innovation programme (Project No. 17FUN07 CC4C and No. 15SIB03 OC18).",
year = "2018",
month = dec,
day = "4",
doi = "10.1103/RevModPhys.90.045005",
language = "English",
volume = "90",
journal = "Reviews of Modern Physics",
issn = "0034-6861",
publisher = "American Physical Society",
number = "4",
}