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arXiv:2610.22574

Two-photon Doppler-free spectroscopy of the $6s^2\;^1S_0 \rightarrow 6s23s\;^1S_0$ Rydberg transition for quantum sensing in ytterbium

B. D. Hunt, K. Beloy, Roger C. Brown, Tobias Bothwell, Harikesh Ranganath, Tanner Grogan, Jacob L. Siegel, Andrew D. Ludlow

Published Oct 15, 2026• 0 citations
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Abstract

Here we report atomic structure calculations and experimental observations of the two-photon $6s^2\;^1S_0 \rightarrow 6s23s\;^1S_0$ transition in Yb. The unique level structure of Yb places the $6s6p\;^1P_1$ state's energy at $\approx\!49.7\%$ of the ionization energy, which facilitates two-photon Doppler-free excitation of the $6s23s\;^1S_0$ Rydberg state from the $6s^2\;^1S_0$ ground state at a relatively low optical intensity. This $J= 0 \rightarrow J=0$ transition is immune to first-order Zeeman and electric quadrupole shifts, has reduced sensitivity to higher-order Zeeman shifts, and is further predicted to have relatively low sensitivity to density shifts. Using configuration interaction theory, we compute relevant properties of the $6s23s\;^1S_0$ Rydberg state for sensing, including the $C_6$ coefficient, dc polarizability, blackbody radiation (BBR) shift, and BBR depopulation rate. As a first experimental step, we demonstrate two-photon Doppler-free spectroscopy of the $6s^2\;^1S_0 \rightarrow 6s23s\;^1S_0$ transition. From our experimental spectra, we estimate the natural linewidth (lifetime) of the $6s23s\;^1S_0$ state to be 90 kHz (1.8 $μ$s). We believe this transition, or other $6s^2\;^1S_0 \rightarrow 6sns\;^1S_0$ transitions in Yb with $n\approx23$, may find use in a variety of sensing applications, potentially including a two-photon clock, electrometer, or BBR thermometer.

DOI
10.48550/arxiv.2610.22574

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Two-photon Doppler-free spectroscopy of the 6s2  1S0→6s23s  1S06s^2\;^1S_0 \rightarrow 6s23s\;^1S_06s21S0​→6s23s1S0​ Rydberg transition for quantum sensing in ytterbium
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