Ultracold $^{88}\rm{Sr}_2$ molecules in the absolute ground state

TL;DR

This paper demonstrates the efficient creation of ultracold $^{88} m{Sr}_2$ molecules in their absolute ground state using all-optical methods, enabling high-precision applications and robust quantum state control.

Contribution

It introduces a novel all-optical technique combining photoassociation and STIRAP to produce large samples of ground-state molecules with high efficiency.

Findings

Over 5500 molecules prepared in the ground state

Two-body loss rates near the universal limit

Enhanced STIRAP efficiency in a magic-wavelength lattice

Abstract

We report efficient all-optical creation of an ultracold gas of alkaline-earth-metal dimers, $^{88}\rm{Sr}_2$, in their absolute ground state. Starting with weakly bound singlet molecules formed by narrow-line photoassociation in an optical lattice, followed by stimulated Raman adiabatic passage (STIRAP) via a singlet-dominant channel in the $(1)0_u^+$ excited potential, we prepare pure samples of more than 5500 molecules in $X^1\Sigma_g^+(v=0,J=0)$. We observe two-body collisional loss rates close to the universal limit for both the least bound and most bound vibrational states in $X^1\Sigma_g^+$. We demonstrate the enhancement of STIRAP efficiency in a magic-wavelength optical lattice where thermal decoherence is eliminated. Our results pave the way for the use of alkaline-earth-metal dimers for high-precision spectroscopy, and indicate favorable prospects for robust quantum state preparation of ultracold molecules involving closed-shell atoms, as well as molecule assembly in deep optical traps tuned to a magic wavelength.