Progress towards spin-squeezing in an ultracold neutral atom ensemble using a superconducting mmwave cavity.

Hybrid quantum platforms aim to combine complementary strengths of different physical platforms to enable improved control and readout of quantum states. In our experiment, we leverage the long coherence times and uniformity of ultracold neutral atom ensembles, the enhanced readout capabilities of optical cavities, and the high-quality factors of superconducting resonators. In this talk, we will present progress toward using an ensemble of Rydberg-dressed atoms coupled to a superconducting bulk-niobium millimeter-wave cavity to generate spin squeezing. Spin control between ground-state hyperfine levels is achieved using Raman transitions, while UV excitation to Rydberg states mediates strong coupling to the millimeter-wave cavity, and an optical cavity enables spin-state-dependent readout of the ensemble. This approach overcomes the cooperativity limitations of traditional optical cavities while retaining the favorable high coherence of atomic spins. We aim to demonstrate the utility of this hybrid architecture by engineering entangled collective states and observing spin squeezing in the atomic ensemble. Beyond metrological enhancement, the strong and unitary interactions achievable in this platform open a path toward preparing more strongly correlated many-body states, including GHZ-type states, with potential applications in quantum simulation and quantum information processing.