Observation of the Hanbury Brown and Twiss Effect with Ultracold Molecules*

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 simulation and quantum computation due to their rich and controllable internal degrees of freedom. However, the detection of correlations between single molecules in an ultracold gas had not been previously demonstrated. We report on the observation of the Hanbury Brown and Twiss effect in a gas of bosonic NaRb, enabled by the realization of a quantum gas microscope for molecules. We detect the characteristic bunching correlations in the density fluctuations of a 2D 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 high-contrast two-molecule interference pattern with a visibility of 54(13)%. Our work paves the way toward realizing other quantum optical phenomena with molecules of increasing complexity.