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# Observation of the Hanbury Brown–Twiss effect with ultracold molecules

## Abstract

Measuring the statistical correlations of individual quantum objects provides an excellent way to study complex quantum systems. Ultracold molecules represent a powerful platform for quantum simulation1 and quantum computation2 due to their rich and controllable internal degrees of freedom. However, the detection of correlations between single molecules in an ultracold gas has yet to be demonstrated. Here we observe the Hanbury Brown–Twiss effect—the emergence of bunching correlations of indistinguishable particles collected by separate detectors—in a gas of bosonic 23Na87Rb Feshbach molecules, enabled by the realization of a molecular quantum gas microscope. We detect the characteristic bunching correlations in the density fluctuations of a two-dimensional molecular gas released from and subsequently recaptured in an optical lattice. The quantum gas microscope allows us to extract the positions of individual molecules with single-site resolution. As a result, we obtain a two-molecule interference pattern with high visibility. Although these measured correlations purely arise from the quantum statistics of the molecules, the demonstrated imaging capabilities open the way for site-resolved studies of interacting molecular gases in optical lattices.

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## Data availability

Source data can be found in the Harvard Dataverse47. All other supporting data are available from the corresponding author upon reasonable request.

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## Acknowledgements

We would like to thank G. Zheng, S. Aggarwal, A. Morningstar and R. Raj for experimental assistance. This work was supported by the NSF (grant no. 1912154) and the David and Lucile Packard Foundation (grant no. 2016-65128). L.C. was supported by the NSF Graduate Research Fellowship Program.

## Author information

Authors

### Contributions

W.S.B. conceived the study and supervised the experiment. J.S.R., L.C., E.G.-S. and Z.Z.Y performed the experiments. J.S.R., L.C. and Z.Z.Y performed the data analysis. All the authors contributed to the article.

### Corresponding author

Correspondence to Waseem S. Bakr.

## Ethics declarations

### Competing interests

The authors declare no competing interests.

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Nature Physics thanks Hanns-Christoph Nägerl and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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## Supplementary information

### Supplementary Information

Supplementary Sections I–IX, Figs. 1–4 and references.

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Rosenberg, J.S., Christakis, L., Guardado-Sanchez, E. et al. Observation of the Hanbury Brown–Twiss effect with ultracold molecules. Nat. Phys. 18, 1062–1066 (2022). https://doi.org/10.1038/s41567-022-01695-9

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