Cold Rydberg atoms for thermometry in optical clocks

Summary: Rydberg atoms are recognized as new promising high sensitivity sensors to detect electro-magnetic fields [1,2] in large frequency bands from DC up to 1 THz, as already implemented on hot atoms with promising results. Here, we propose to apply this technique to measure the Black-Body Radiation (BBR) field in an optical lattice clock (OLC) [3,4]

OLCs are ultra-high precision frequency standards based on probing a narrow optical transition in trapped cold atoms [5]. Currently, the BBR-induced frequency shift, in the low 10-18, remains a major limitation for the accuracy of OLCs. Within a new joint project, LAC and SYRTE aim at implementing Rydberg atom thermometry to allow in-situ temperature measurements within the clock’s cold atomic cloud, in order to improve the clock accuracy.

The objective of the internship, co-hosted by LAC and SYRTE, is to implement a new servo-lock on a Rydberg excitation laser on a spectroscopic signal at LAC and to implement a new laser for Rydberg excitation on a Sr OLC at SYRTE. These developments will lead to the observation of Rydberg excitation.

This internship can be prolonged by a PhD, in joint supervision between LAC and SYRTE. Observation of BBR-induced transfers between Rydberg states, and confrontation with theory, will be first realized on a dedicated experiment at LAC. Then, these results will be transposed in a state-of-the art OLC at SYRTE, where the determination of the BBR field with Rydberg atoms will be compared to standard thermometry and a finite element model of the vacuum environment of the clock.

[1] Atom based RF electric field sensing, H. Fan et al., J. Phys. B 48, 202001 (2015)
[2] Assessment of Rydberg atoms for wideband electric field sensing, D. H. Meyer et al., J. Phys. B 53, 034001 (2020)
[3] Rydberg Spectroscopy in an Optical Lattice: Blackbody Thermometry for Atomic Clock V. D. Ovsiannikov et al., PRL 107, 093003 (2011)
[4] Quantum blackbody thermometry, E. B. Norrgard et al., NJP 23, 033037 (2021)
[5] Optical atomic clocks, A. D. Ludlow et al, Rev. Mod. Phys. 87, 637 (2015)

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