Mainz 2026 – scientific programme
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A: Fachverband Atomphysik
A 14: Poster – Precision Spectroscopy of Atoms and Ions (joint session A/Q)
A 14.8: Poster
Tuesday, March 3, 2026, 17:00–19:00, Philo 1. OG
Calcium optical clock as an absolute frequency standard for the thorium nuclear transition — •Darius Fenner1, Valerii Andriushkov1,2, Keerthan Subramanian1, Ke Zhang1, Srinivasa Pradeep Arasada1, Florian Zacherl1, Yumiao Wang1,4, Christoph E. Düllmann1,2, Dmitry Budker1,2,3, Ferdinand Schmidt-Kaler1, and Lars von der Wense1 — 1Johannes Gutenberg-Universität Mainz — 2Helmholtz Institut Mainz — 3University of California, Berkeley, USA — 4Fudan University, Shanghai, China
Nuclear clocks are expected to improve the accuracy of optical clocks due to their reduced susceptibility to external fields and higher transition frequencies. They are based on the transition of the low-lying and long-lived isomeric state of thorium-229. In our setup, thorium and calcium ions are co-trapped in a linear Paul trap for sympathetic cooling. In the future, to excite the thorium nucleus with a cw laser, the frequency of the nuclear transition must be compared to a known frequency standard. This poster presents the construction of an optical clock based on a trapped Ca+ ion, using the 729 nm clock transition between S1/2 and D5/2. The clock laser is first stabilized using the Pound-Drewer-Hall technique to reach a linewidth at the Hertz level. After locking the laser to the calcium ion, its frequency will be measured using an optical frequency comb. The goal is to reach an accuracy of 10−15. This project is supported by the BMFTR Quantum Futur II Grant Project NuQuant (FKZ 13N16295A) and DFG Project TACTICa (grant agreement no. 495729045).
Keywords: Atomic Clock; Nuclear Clock