Mainz 2026 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 61: Matter Wave Interferometry and Metrology III
Q 61.4: Talk
Thursday, March 5, 2026, 15:15–15:30, P 11
Ramsey-Bordé Interferometry with a Thermal Strontium Beam for a Compact Optical Clock — •Oliver Fartmann1, Marc Christ2, Amir Mahdian1,2, Levi Wihan1, and Markus Krutzik1,2 — 1Humboldt-Universität, Inst. f. Physik, Newtonstr. 15, 12489 Berlin — 2Ferdinand-Braun-Institut (FBH), Gustav-Kirchhoff-Straße 4, 12489 Berlin
Compact optical clocks based on Ramsey-Bordé interferometry (RBI) with a thermal atomic beam offer higher stability than optical vapour cell clocks while being less complex than cold atom clocks.
This talk presents the realization of strontium RBI on the narrow 1S0 → 3P1 intercombination line at 689 nm. A structured optimization of major subsystems was carried out, including clock-laser pre-stabilization to a high-finesse cavity, successive improvements to the atomic oven, spectroscopy-based error-signal generation, feedback loop, and a systematic evaluation of clock stability limitations.
Our first operating RBI-clock demonstrated fractional frequency instabilities below σy(τ) < 10−13 for averaging times between 1 s and 1000 s, with residual temperature fluctuations identified as the dominant limitation. Building on these results, two additional portable RBI spectroscopy setups were developed, with volumes of only 20 l. Initial instability measurements and the uncertainty budget will be presented.
These systems serve as ground-based demonstrators and testbeds, paving the way for mobile and space-deployable optical clocks.
[1] O. Fartmann et al. EPJ Quantum Techn. 12, 31 (2025).
Keywords: Clock; Ramsey-Bordé; Atom interferometer; Strontium; Cavity