A thorium-229 optical nuclear clock with feedback loop.
9 affiliations
- 1Vienna Center for Quantum Science and Technology, Atominstitut, TU Wien, Vienna, Austria
- 2Bundesamt für Eich- und Vermessungswesen (BEV), Vienna, Austria
- 3Wolfgang Pauli Institut, Vienna, Austria
- 4Institut für Erdmessung, Leibniz Universität Hannover, Hanover, Germany
- 5Institute of Scientific Instruments, CAS v. v. i., Brno, Czech Republic
- 6Physikalisch-Technische Bundesanstalt (PTB), Braunschweig, Germany
- 7Max-Born-Institute for Nonlinear Optics and Ultrafast Spectroscopy, Berlin, Germany
- 8Physikalisch-Technische Bundesanstalt (PTB), Braunschweig, Germany. [email protected]
- 9Vienna Center for Quantum Science and Technology, Atominstitut, TU Wien, Vienna, Austria. [email protected]
Abstract
The laser-accessible nuclear transition in the thorium-229 isotope has been identified as a candidate for realizing an optical nuclear clock¹ that might outperform current optical clocks based on electron-shell transitions in atoms or ions². It is expected to be more robust against external perturbations3,4 and to provide enhanced sensitivity in clock-based tests of the fundamental principles of physics5,6. Here we realize a thorium-229 nuclear clock by stabilizing a continuous-wave laser to the 148-nm nuclear transition with rapid feedback based on absorption spectroscopy⁷. The thorium-229 nuclei are embedded in a millimetre-sized, room-temperature calcium fluoride crystal. A subharmonic of the 148-nm radiation is continuously compared with a Yb⁺ single-ion clock. The nuclear clock shows a shot-noise-limited fractional frequency instability of 3×10-12/τ/s where τ is the averaging time, approaching 10⁻¹⁵ instabilities over 1 day of operation. Improvements to the instability by several orders of magnitude are projected for future devices. We use the nuclear clock to constrain models of ultralight dark matter by searching for periodic fluctuations and slow drifts in the nuclear transition energy, on timescales between 20 s and 1 day. Benefitting from the enhanced sensitivity of the thorium-229 transition, these constraints compete with the best atomic clocks concerning dark matter coupling to photons and go beyond previous measurements regarding coupling to the strong force.
Related
- Optical cycling on thorium monoxide (ThO) for an improved test of fundamental symmetries
- Feedback-Enhanced Quantum Metrology and Clock Precision under Thermodynamic Uncertainty
- A solid-state nuclear clock based on VUV absorption spectroscopy of 229Th
- Origin of the inhomogeneous linewidth in a solid state 229Th:CaF2 nuclear clock
- Optical Signals Synthesized from an Optical Lattice Clock with Uncertainty of 1.3E-17
BibTeX
@article{col2026thorium229,
title = {{A thorium-229 optical nuclear clock with feedback loop.}},
author = {L. Toscani De Col and Thomas Riebner and I. Morawetz and F. Schneider and N. Sempelmann and Juliette Schlachet-Lépinay and Fabian Schaden and Michael Bartokos and Georgy A. Kazakov and Kjeld Beeks and B. Gerstenecker and Martin Pimon and Sebastian Lahs and Andreas Hellerschmied and T. Lercher and Heiner Denker and Jörg Premper and A. Niessner and Michael Matus and M. (Martin) Čížek and O. (Ondřej) Číp and V. Lal and G. Zitzer and V. Petrov and Johannes Tiedau and Maksim V. Okhapkin and E. Peik and Thorsten Schumm},
journal = {Nature},
year = {2026},
month = oct,
doi = {10.1038/s41586-026-11084-4},
url = {https://europepmc.org/article/MED/42844480},
note = {CC BY},
}
RIS
TY - JOUR
TI - A thorium-229 optical nuclear clock with feedback loop.
AU - L. Toscani De Col
AU - Thomas Riebner
AU - I. Morawetz
AU - F. Schneider
AU - N. Sempelmann
AU - Juliette Schlachet-Lépinay
AU - Fabian Schaden
AU - Michael Bartokos
AU - Georgy A. Kazakov
AU - Kjeld Beeks
AU - B. Gerstenecker
AU - Martin Pimon
AU - Sebastian Lahs
AU - Andreas Hellerschmied
AU - T. Lercher
AU - Heiner Denker
AU - Jörg Premper
AU - A. Niessner
AU - Michael Matus
AU - M. (Martin) Čížek
AU - O. (Ondřej) Číp
AU - V. Lal
AU - G. Zitzer
AU - V. Petrov
AU - Johannes Tiedau
AU - Maksim V. Okhapkin
AU - E. Peik
AU - Thorsten Schumm
PY - 2026
DA - 2026/10/07
JO - Nature
DO - 10.1038/s41586-026-11084-4
UR - https://europepmc.org/article/MED/42844480
AB - The laser-accessible nuclear transition in the thorium-229 isotope has been identified as a candidate for realizing an optical nuclear clock¹ that might outperform current optical clocks based on electron-shell transitions in atoms or ions². It is expected to be more robust against external perturbations3,4 and to provide enhanced sensitivity in clock-based tests of the fundamental principles of physics5,6. Here we realize a thorium-229 nuclear clock by stabilizing a continuous-wave laser to the 148-nm nuclear transition with rapid feedback based on absorption spectroscopy⁷. The thorium-229 nuclei are embedded in a millimetre-sized, room-temperature calcium fluoride crystal. A subharmonic of the 148-nm radiation is continuously compared with a Yb⁺ single-ion clock. The nuclear clock shows a shot-noise-limited fractional frequency instability of 3×10-12/τ/s where τ is the averaging time, approaching 10⁻¹⁵ instabilities over 1 day of operation. Improvements to the instability by several orders of magnitude are projected for future devices. We use the nuclear clock to constrain models of ultralight dark matter by searching for periodic fluctuations and slow drifts in the nuclear transition energy, on timescales between 20 s and 1 day. Benefitting from the enhanced sensitivity of the thorium-229 transition, these constraints compete with the best atomic clocks concerning dark matter coupling to photons and go beyond previous measurements regarding coupling to the strong force.
SN - 0028-0836
SN - 1476-4687
ER -