Collective resonance of $D$ states in rubidium atoms probed by optical two-dimensional coherent spectroscopy

TL;DR

This paper demonstrates the observation of collective resonances in rubidium atoms in higher excited $D$ states using optical two-dimensional coherent spectroscopy, revealing new insights into many-body quantum interactions.

Contribution

It reports the first observation of collective resonance in rubidium $D$ states, extending understanding beyond $P$ states with a novel spectroscopic approach.

Findings

Collective resonances observed in rubidium $D$ states.

Spectra accurately reproduced by optical Bloch equation simulations.

Technique enables probing of collective resonances in highly excited atomic states.

Abstract

Collective resonance of interacting particles has important implications in many-body quantum systems and their applications. Strong interactions can lead to a blockade that prohibits the excitation of a collective resonance of two or more nearby atoms. However, a collective resonance can be excited with the presence of weak interaction and has been observed for atoms in the first excited state ($P$ states). Here, we report the observation of collective resonance of rubidium atoms in a higher excited state ($D$ states) in addition to the first excited state. The collective resonance is excited by a double-quantum four-pulse excitation sequence. The resulting double-quantum two-dimensional (2D) spectrum displays well-isolated peaks that can be attributed to collective resonances of atoms in $P$ and $D$ states. The experimental one-quantum and double-quantum 2D spectra can be reproduced by a simulation based on the perturbative solutions to the optical Bloch equations, confirming collective resonances as the origin of the measured spectra. The experimental technique provides a new approach for preparing and probing collective resonances of atoms in highly excited states.