Preparation of Long-Lived, Non-Autoionizing Circular Rydberg States of Strontium

TL;DR

This paper demonstrates the creation of long-lived, non-autoionizing circular Rydberg states in strontium atoms, enabling their trapping, cooling, and potential use in quantum interfaces due to their stability and optical properties.

Contribution

It introduces a method to produce long-lived circular Rydberg states in strontium with a metastable core, overcoming autoionization issues present in low-angular-momentum states.

Findings

Strontium circular Rydberg states are impervious to autoionization for milliseconds.

Core excitation enables optical manipulation and transitions between singlet and triplet states.

Potential for quantum microwave to optical interfaces using these stable Rydberg states.

Abstract

Alkaline earth Rydberg atoms are very promising tools for quantum technologies. Their highly excited outer electron provides them with the remarkable properties of Rydberg atoms and, notably, with a huge coupling to external fields or to other Rydberg atoms while the ionic core retains an optically active electron. However, low angular-momentum Rydberg states suffer almost immediate autoionization when the core is excited. Here, we demonstrate that strontium circular Rydberg atoms with a core excited in a $4D$ metastable level are impervious to autoionization over more than a few millisecond time scale. This makes it possible to trap and laser-cool Rydberg atoms. Moreover, we observe singlet to triplet transitions due to the core optical manipulations, opening the way to a quantum microwave to optical interface.