A cryogenic pulsed supersonic beam source of metastable helium with chirped laser slowing for hybrid circuit QED

Hybrid cavity QED experiments in which Rydberg atoms are interfaced with superconducting microwave circuits are of interest for optical-to-microwave photon conversion, and the implementation of quantum networks. The use of He atoms in this setting provides an effective means to minimize the impact of adsorbates and stray electric fields emanating from the cryogenically cooled superconducting chip surfaces [1]. Rydberg He atoms in pulsed supersonic beams have been coherently coupled to superconducting coplanar waveguide microwave resonators, with single-photon Rabi frequencies on the order of 100 Hz [2]. To extend the atom-resonator interaction times and enhance coupling strengths in these experiments, it is now necessary to laser slow and cool the atoms. In this talk, I will describe our apparatus for chirped laser slowing cryogenically cooled (~20K) pulsed supersonic beams of metastable He (mean speed ~500 m/s). This involves the use of a narrow bandwidth fiber laser at 1083 nm which is resonant with the 2³S₁ to 2³P₂ transition [3,4]. Our experimental data are compared to the results of numerical particle trajectory calculations to support their interpretation. These methods will in the future offer the opportunity to prepare arrays of Rydberg He atoms above superconducting circuits.

[1] A. A. Morgan et al. Phys. Rev. Lett. 124, 193604 (2020)

[2] L. L. Brown et al. Phys. Rev. A 113, 013709 (2026)

[3] A. Aspect et al. Chem. Phys. 145, 307 (1990)

[4] W. Rooijakkers et al. Opt. Commun. 123, 321 (1996)