Multiphoton dressed Rydberg excitations in a microwave cavity with ultracold Rb atoms

TL;DR

This study explores multiphoton Rydberg excitations of ultracold rubidium atoms within a microwave cavity, revealing complex spectral features and photon emission behaviors relevant for quantum sensing and hybrid quantum systems.

Contribution

It introduces a novel spectroscopic approach combining Rydberg atoms with a microwave cavity, modeled by an extended Jaynes-Cummings formalism, to analyze multiphoton processes and cavity interactions.

Findings

Observation of ladder multiphoton microwave Rydberg absorption and emission.

Evidence for fractional photon emission into cavity modes.

Modeling of spectra with extended Jaynes-Cummings formalism.

Abstract

We investigate magneto-optical trap loss spectroscopy of Rydberg excited $^{85}$Rb ($66\leq n \leq 68~S_{1/2}$) atoms, placed inside a tailored microwave cavity. The cavity frequency at 13.053 GHz is in resonance with the $67S_{1/2} \rightarrow 66P_{3/2}$ transition, inducing a ladder multiphoton microwave Rydberg absorption and emission. The observed spectra are modeled with an extended Jaynes-Cumming formalism that accounts for multiphoton absorption from and emission into the cavity, the loss from the trap due to Rydberg excitation, and cavity imperfection. We calculate the average photons in each spectral feature and find evidence for fractional photon emission into the cavity modes. The microwave cavity Rydberg spectroscopy in this work should inform the application and technology development of Rydberg based sensors and hybrid Rydberg atom-superconducting resonator quantum gates.