DEPARTMENT OF PHYSICS DISSERTATION DEFENSE: Michelle Wu

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Title:   Schrödinger Cat States from Emergent Collective Dynamics in a Dipolar Rydberg Atom ArrayAbstract:   Dipolar interactions arise naturally across diverse platforms, including Rydberg atoms, polar molecules, solid-state spins, and magnetic atoms. Their long-range character supports collective many-body dynamics conducive to scalable generation of entanglement. These dynamics theoretically provide access to Schrödinger cat states constituting resources for Heisenberg-limited metrology, yet such states are notoriously fragile to detection errors. We address this challenge experimentally in a Rydberg-atom array, harnessing the native dipolar spin-exchange coupling both for the generation of Schrödinger cat states and for robust interaction-based readout. The generation of collective entanglement from local dipolar interactions is enabled by the low-energy spectrum of the spin-exchange Hamiltonian, which resembles a paradigmatic model of globally interacting spins, the one-axis-twisting Hamiltonian. We verify the collective nature of the dynamics by probing spatial correlations and characterize the resulting cat state by performing phase-space tomography of the collective spin. To robustly quantify many-body coherence and entanglement, we employ a decoding protocol that converts collective phase information into a macroscopic oscillation in the collective magnetization. Building on our demonstration in chains of up to 12 atoms, I discuss routes to scalability, including extending to two-dimensional arrays with enhanced connectivity and coupling Rydberg atoms to a superconducting millimeter-wave cavity. These directions offer prospects for quantum-enhanced sensing, long-range entangling gates, and the exploration of many-body physics arising from the interplay of direct dipolar and cavity-mediated interactions.