# Multi-state detection and spatial addressing in a microscope for ultracold molecules

## TL;DR

The paper presents a new microscope technique to detect and study individual ultracold molecules in bulk samples with high spatial resolution.

## Contribution

The work introduces a method for spatially resolved detection of single 87Rb133Cs molecules using fluorescence from dissociated atoms.

## Key findings

- Individual molecules are detected with sub-micron resolution in a deep optical lattice.
- The method allows for measuring density-dependent collisional losses in small molecular samples.
- Local addressing of molecules is achieved via spatially-dependent light shifts on rotational transitions.

## Abstract

Precise measurement of the particle number, spatial distribution and internal state is fundamental to all proposed experiments with ultracold molecules both in bulk gases and optical lattices. Here, we demonstrate in-situ detection of individual molecules in a bulk sample of 87Rb133Cs molecules. Extending techniques from atomic quantum gas microscopy, we pin the molecules in a deep two-dimensional optical lattice and, following dissociation, collect fluorescence from the constituent atoms using a high-numerical-aperture objective. This enables detection of individual molecules up to the resolution of the sub-micron lattice spacing. Our approach provides direct access to the density distribution of small samples of molecules, allowing us to obtain precise measurements of density-dependent collisional losses. Further, by mapping two internal states of the molecule to different atomic species, we demonstrate simultaneous detection of the position and rotational state of individual molecules. Finally, we implement local addressing of the sample using a focused beam to induce a spatially-dependent light shift on the rotational transitions of the molecules.

Detection of ultracold molecules based on absorption imaging have inherent limitations. Here, the authors demonstrate spatially resolved detection of single ultracold 87Rb133Cs molecules in the bulk, extending recent microscopy developments from ultracold atoms to molecules.