Cs Molecules*

Ultracold Polar molecules, with their strong dipolar interactions and complex internal structure, offer a highly versatile platform for exploring quantum many-body physics. Here we present progress toward realizing strongly correlated systems of RbCs molecules in a quantum gas microscope. We aim to combine the especially long coherence times [1] and high-fidelity state readout [2] of this species with the ability to resolve microscopic correlations demonstrated in NaRb [3].

We report on a newly developed apparatus designed for molecular microscopy. Using fast optical transport [4], we sequentially load ⁸⁷Rb and ¹³³Cs gases to create spatially separated condensates within the field of view of a high numerical aperture (NA = 0.7) lens. From this mixture, we prepare ground state molecules in an optical lattice and have achieved single-site resolved fluorescence imaging of both atomic species following dissociation on the lattice sites. This dual-species imaging capability enables complete reconstruction of the spin system encoded in the molecules [5]. We also discuss the ongoing development of the apparatus to incorporate magic wavelength trapping and the potential for producing low-entropy gases via merging an atomic bilayer system.

 

[1] D. K. Ruttley, T. R. Hepworth, A. Guttridge, and S. L. Cornish, Long-lived entanglement of molecules in magic-wavelength optical tweezers, Nature 637, 827 (2025).

[2] B. P. Maddox, J. M. Mortlock, T. R. Hepworth, A. P. Raghuram, P. D. Gregory, A. Guttridge, and S. L. Cornish, Enhanced Quantum State Transfer via Feedforward Cancellation of Optical Phase Noise, Phys. Rev. Lett. 133, 253202 (2024).

[3] L. Christakis, J. S. Rosenberg, R. Raj, S. Chi, A. Morningstar, D. A. Huse, Z. Z. Yan, and W. S. Bakr, Probing site-resolved correlations in a spin system of ultracold molecules, Nature 614, 7946 (2023). 

[4] A. J. Matthies, J. M. Mortlock, L. A. McArd, A. P. Raghuram, A. D. Innes, P. D. Gregory, S. L. Bromley, and S. L. Cornish, Long-distance optical-conveyor-belt transport of ultracold Cs 133 and Rb 87 atoms, Phys. Rev. A 109, 023321 (2024).

[5] J. P. Covey, L. D. Marco, O. L. Acevedo, A. M. Rey, and J. Ye, An approach to spin-resolved molecular gas microscopy, New Journal of Physics 20, (2018).