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arXiv:2512.14885 · Scientific Reports

Hyperfine spectroscopy of optical-cycling transitions in singly ionized thulium

Patrick Müller, Andrei Tretiakov, Amanda Younes, Nicole Halawani, Paul Hamilton, Wesley C. Campbell

physics.atom-phquant-phSubmitted Dec 16, 2025• Announced Dec 18, 2025• 1 citation
v1 · Dec 16, 2025v2 · Apr 4, 2026
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Abstract

We present a spectroscopic investigation of $^{169}\mathrm{Tm}^+$ that provides two key foundations for its use as a platform for advanced quantum applications. First, we establish the complete spectroscopic road map for optical cycling (including laser cooling) by performing high-resolution spectroscopy on $^{169}\mathrm{Tm}^+$ ions in an ion trap. We characterize the primary $313\,\mathrm{nm}$ and complementary $448/453\,\mathrm{nm}$ cycling transitions, identify the essential near-infrared repumping frequencies, and determine the magnetic-dipole hyperfine $A$ constants for all relevant levels. Second, we report detailed characterization of a metastable state as a candidate for hosting a robust qubit, performing lifetime measurements and Zeeman-resolved microwave hyperfine spectroscopy with $\mathrm{kHz}$ precision.

Journal reference
Scientific Reports 16, 10655 (2026)
DOI
10.1038/s41598-026-45288-5
Comments
10 pages, 5 figures

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We present a spectroscopic investigation of 169Tm+^{169}\mathrm{Tm}^+169Tm+ that provides two key foundations for its use as a platform for advanced quantum applications. First, we establish the complete spectroscopic road map for optical cycling (including laser cooling) by performing high-resolution spectroscopy on 169Tm+^{169}\mathrm{Tm}^+169Tm+ ions in an ion trap. We characterize the primary 313 nm313\,\mathrm{nm}313nm and complementary 448/453 nm448/453\,\mathrm{nm}448/453nm cycling transitions, identify the essential near-infrared repumping frequencies, and determine the magnetic-dipole hyperfine AAA constants for all relevant levels. Second, we report detailed characterization of a metastable state as a candidate for hosting a robust qubit, performing lifetime measurements and Zeeman-resolved microwave hyperfine spectroscopy with kHz\mathrm{kHz}kHz precision.
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Thulium atoms are trapped in a magneto-optical trap using a strong transition at 410410410 nm with a small branching ratio. We trap up to $7\ifmmode\times\else\texttimes\fi{}{10}^{4}$ atoms at a temperature of 0.8(2)0.8(2)0.8(2) mK after deceleration in a 404040-cm-long Zeeman slower. Optical leaks from the cooling cycle influence the lifetime of atoms in the magneto-optical trap which varies between 0.30.30.3 and 1.51.51.5 s in our experiments. The lower limit for the leaking rate from the upper cooling level is measured to be 22(6)22(6)22(6) ${\mathrm{s}}^{\ensuremath{-}1}$. The repumping laser transferring the atomic population out of the F=3F=3F=3 hyperfine ground-state sublevel gives a 3030%30 increase for the lifetime and the number of atoms in the trap.
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