ECAMP 15

The relentless pursuit of higher precision in optical lattice clocks (OLC) demands ever more refined methods to mitigate environmental perturbations, with blackbody radiation (BBR) induced frequency shifts standing as a major challenge. State-of-the-art OLCs address this effect by either operating in a cryogenic environment to reduce the BBR [1], by employing comprehensive temperature monitoring and compensation techniques in room-temperature setups [2] or by shielding the in-vacuum radiation inhomogeneities [3].

Atoms excited to Rydberg states have been proposed, due to their enhanced sensitivity to BBR [4], as excellent candidates for in-situ and calibration-free measurements of the BBR spectrum experienced by atoms in OLCs [5]. This approach relies on measuring the BBR-induced energy shifts of Rydberg states but is challenging due to the absence of a well-defined reference state. To overcome this limitation, a method based on BBR-induced state transfers has been proposed [6]. A theoretical model, developed alongside new experimental results using alkali Rubidium atoms [7], demonstrates promising initial results and a first validation of this technique.

Until now, proposed methods and models have relied on Rydberg physics in alkali atoms, whereas OLCs are based on alkaline-earth atoms. Divalent atoms introduce new challenges in the theoretical treatment of Rydberg physics, which is already complex for alkali atoms. However, the presence of two valence electrons in alkaline-earth Rydberg atoms unlocks a range of new behaviors and phenomena [8]. We will present a new theoretical protocol, specific to divalent Rydberg atoms, harnessing their unique effects. We will then analyze its merit compared to the existing protocols. An experiment is currently being built to demonstrate the feasibility of this method.

[1] I. Ushijima et al. Nature Photonics 9, 185–189, (2015)
[2] Y. Foucault et al. Joint Conference of the European Frequency and Time Forum and IEEE International Frequency Control Symposium (EFTF/IFCS), (2021)
[3] K. Beloy et al. Phys. Rev. Lett. 113, 260801, (2014)
[4] T.F. Gallagher. Cambridge Monographs on Atomic, Molecular, and Chemical Physics, (1994)
[5] V.D. Ovsiannikov et al. Phys. Rev. Lett. 107, 093003, (2011)
[6] E.B. Norrgard et al. New J. Phys. 23, 033037, (2021)
[7] N. Schlossberger al. Phys. Rev. Research 7, L012020, (2025)
[8] K.L. Pham et al. PRX Quantum 3, 020327, (2022)