Andrés Durán-Hernández

Generation of large-field optical tweezers and observation of spin-exchange dynamics between two trapped circular Rydberg atoms

This thesis develops and exploits a room-temperature platform for quantum simulation with optically trapped circular Rydberg states of rubidium. The core of the work is a single-element hybrid architecture in which circular states encode the data degree of freedom, while optically accessible low-ℓ Rydberg ancillae enable local addressing, conditional operations, and readout. These capabilities rely on operation near a Förster resonance. A first part of the thesis addresses a major scalability bottleneck of wide-field tweezer arrays: optical aberrations that degrade trap quality away from the optical axis. We present an atom-based method to calibrate a field-dependent wavefront-distortion model. This model is a central component of an array-generation algorithm developed previously within the team, enabling site-wise aberration correction at the programmed tweezer positions. Using the commercial aspheric lens integrated in our experimental setup, we obtain homogeneous, near-diffraction-limited traps over a 150 x 342 µm2 field of view, ultimately limited by optical clipping.

Building on these tools, we realize hybrid arrays combining bottle-beam traps for circular atoms and Gaussian tweezers for ancilla atoms. We then observe coherent resonant dipole-dipole spin-exchange (flip-flop) dynamics between two circular atoms prepared in |53C;54C❭. The ancilla layer intervenes at three stages: it enables conditional preparation of the circular-atom pair state, contributes to a post-selection signal that identifies successful runs, and enables readout of the circular data-atom state. Because the ancilla is optically accessible, it provides local control and measurement of otherwise optically dark circular states.
 
These results constitute a proof-of-principle for ancilla-enabled quantum simulation with circular Rydberg atoms in a hybrid platform. They motivate near-term upgrades that directly target the identified limitations, in particular cryogenic operation to access the long intrinsic lifetime of circular states, and efficient motional cooling to prepare atoms close to the motional ground state. By extending coherence times and reducing motion-induced damping, these upgrades would expand the accessible parameter regime and could enable the observation of hundreds of exchange oscillations with near-unit contrast. Combined with the site-resolved local control and non-destructive readout enabled by the ancilla layer, these upgrades would enable larger programmable arrays to probe slow many-body dynamics. With further improvements, for instance in fast and high-fidelity imaging, they would also pave the way for ancilla-assisted mid-circuit measurements.