Molecular Assembly of Ground-State Cooled Single Atoms

Abstract

We demonstrate full quantum state control of two species of single atoms using optical tweezers and assemble the atoms into a molecule. Our demonstration includes 3D ground-state cooling of a single atom (Cs) in an optical tweezer, transport by several microns with minimal heating, and merging with a single Na atom. Subsequently, both atoms occupy the simultaneous motional ground state with 61(4)% probability. This realizes a sample of exactly two cotrapped atoms near the phase-space-density limit of one, and allows for efficient stimulated-Raman transfer of a pair of atoms into a molecular bound state of the triplet electronic ground potentiala3Σ+. The results are key steps toward coherent creation of single ultracold molecules for future exploration of quantum simulation and quantum information processing.

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Plain Language Summary

Building complex quantum systems one molecule at a time is a promising approach to applications such as exploring quantum chemistry or building quantum computers. This technique hinges on the ability to generate and precisely control ultracold molecules. Here, we experimentally demonstrate key steps of such a molecular assembler, allowing us to trap, transport, and merge two different atoms.

Building on our earlier work, we trap one sodium and one cesium atom in separate optical tweezers, bring them together, then trigger the formation of an NaCs molecule with a laser pulse. To further push this reaction to its quantum mechanical limit, we add steps to purify the quantized motion of the atoms into their lowest energy state in the tweezer. As a result, we are able to turn 70% of sodium-cesium atom pairs into electronic ground-state molecules.

In the future, we envision that “designer” molecules for quantum computing and simulation would be assembled using this method, where full quantum control of the initial atoms and resulting molecule can be achieved.