Neutral atoms in optical tweezers have emerged as a highly promising platform, offering long intrinsic coherence times, the ability to arrange qubits in flexible, reconfigurable geometries, and the capacity for fast entangling gates mediated by strong Rydberg interactions. However, their advancement towards large-scale quantum processing is often impeded by several key limitations. These include slow or destructive qubit readout methodologies, probabilistic array preparation which necessitates time-consuming atom rearrangement, and cooling techniques that can be dependent on specific atomic internal structures or require complex experimental geometries. This thesis addresses these critical challenges by detailing the first applications of a novel experimental system that integrates an array of neutral cesium atoms with a high-cooperativity (𝜂 > 20) four-mirror optical bow-tie cavity. We first leverage our optical resonator to demonstrate fast, non-destructive, and number-resolved readout of individual atoms. This capability enables the real-time observation of light-assisted collisional dynamics and underpins an adaptive feedback protocol that achieves quasi-deterministic single-atom loading with a 92(2)% success probability. Building on this robust control, we utilize the cavity’s unique properties—including a narrow linewidth and intrinsic running-wave modes—to realize efficient three-dimensional cooling near the ground state and report the first demonstration of programmable few-atom Bragg scattering in a bow-tie resonator. To address the overarching challenge of optimizing complex, high-dimensional experimental systems, we then pioneer the use of machine learning for atomic cooling. We introduce a deep reinforcement learning agent, trained via a sim-to-real protocol, that learns to actively cool a single atom more rapidly than conventional methods. In a separate demonstration, we apply Bayesian optimization to the multi-parameter landscape of magneto-optical trap compression and polarization gradient cooling to produce a Bose-Einstein condensate directly from polarization gradient cooling. Collectively, these results establish the integration of bow-tie cavities and machine intelligence as a powerful paradigm for building the next generation of robust, scalable, and high-fidelity neutral-atom quantum processors.
Neutral atoms in optical tweezers have emerged as a highly promising platform, offering long intrinsic coherence times, the ability to arrange qubits in flexible, reconfigurable geometries, and the capacity for fast entangling gates mediated by strong Rydberg interactions. However, their advancement towards large-scale quantum processing is often impeded by several key limitations. These include slow or destructive qubit readout methodologies, probabilistic array preparation which necessitates time-consuming atom rearrangement, and cooling techniques that can be dependent on specific atomic internal structures or require complex experimental geometries. This thesis addresses these critical challenges by detailing the first applications of a novel experimental system that integrates an array of neutral cesium atoms with a high-cooperativity (𝜂 > 20) four-mirror optical bow-tie cavity. We first leverage our optical resonator to demonstrate fast, non-destructive, and number-resolved readout of individual atoms. This capability enables the real-time observation of light-assisted collisional dynamics and underpins an adaptive feedback protocol that achieves quasi-deterministic single-atom loading with a 92(2)% success probability. Building on this robust control, we utilize the cavity’s unique properties—including a narrow linewidth and intrinsic running-wave modes—to realize efficient three-dimensional cooling near the ground state and report the first demonstration of programmable few-atom Bragg scattering in a bow-tie resonator. To address the overarching challenge of optimizing complex, high-dimensional experimental systems, we then pioneer the use of machine learning for atomic cooling. We introduce a deep reinforcement learning agent, trained via a sim-to-real protocol, that learns to actively cool a single atom more rapidly than conventional methods. In a separate demonstration, we apply Bayesian optimization to the multi-parameter landscape of magneto-optical trap compression and polarization gradient cooling to produce a Bose-Einstein condensate directly from polarization gradient cooling. Collectively, these results establish the integration of bow-tie cavities and machine intelligence as a powerful paradigm for building the next generation of robust, scalable, and high-fidelity neutral-atom quantum processors.
Neutral atom arrays have rapidly emerged as a leading platform for quantum computing, boasting scalable, configurable arrays of single atoms trapped in optical tweezers, fast, high-fidelity entangling gates through Rydberg interactions, and programmable, parallelized control of qubit operations. Coupling an atom array to an optical cavity opens a new frontier. Leveraging enhanced light-atom interactions in cavity quantum electrodynamics, cavity- coupled atom arrays acquire capabilities that can further expand the neutral atom toolbox, including cavity-enhanced atom readouts, atom-photon entanglement, and photon-mediated interactions between distant atoms. This thesis presents a quantum hardware platform that integrates an array of neutral atoms with a high-finesse optical cavity. After describing the design and development of the experimental apparatus, I demonstrate high-fidelity atom state readout through the cavity, achieving improved speed and atom survival compared to conventional free-space imaging methods. I then introduce a new technique for selectively controlling atom-cavity coupling on arbitrary subsets of the array, using local AC Stark shifts on the excited states of the atoms. Building on these tools, I demonstrate fast, non-destructive cavity-based readout of atom arrays, a crucial bottleneck of atom array platforms. I also showcase real-time measurement and feedback capabilities with a demonstration of classical error correction, using a register of atomic bits. Finally, I describe progress toward implementing single- and two-qubit gates within the cavity-coupled system. By combining coherent control, tunable interactions, and high-fidelity, non-destructive readout integrated and real-time feedback, the cavity-coupled Rydberg atom array offers a promising path toward fault-tolerant quantum computing.
Neutral-atom array and cavity quantum electrodynamics offer complementary strengths for quantum science: scalable, reconfigurable qubit architectures and strong coherent light-matter coupling. Combining them in a single platform requires an optical cavity with simultaneously high cooperativity, sufficient mode volume to accommodate atom array, and ample side optical access for atom trapping, imaging, cooling, and rearrangement, a combination that is challenging to achieve. Here we realize an atomic array integrated with a millimeter-scale Fabry--Pérot cavity whose optically-characterized single-atom cooperativity reaches ηcav=125±13. Atom-cavity transmission spectra of trapped atoms yield an effective spectroscopic cooperativity ηspec=106±3, providing an in-situ verification of strong coupling in the integrated platform. In this integrated system, we achieve a state-measurement fidelity of 99.925−18+15% for a single atom with a 4-μs readout time. We also demonstrate simultaneous coupling of up to 21 individually trapped atoms to the antinode of the cavity mode. The key technical advance is a two-step mirror-fabrication method combining precision mechanical shaping and carbon-dioxide laser polishing, which produces concave fused-silica mirrors with sub-millimeter radii of curvature and residual roughness below 2A˚. Our results establish a regime of cavity-integrated atomic array that simultaneously provides high cooperativity, large mode volume, and flexible manipulation of individual atoms, opening opportunities for cavity-assisted quantum state readout and long-range entanglement-engineering in atom-array platforms.
This dissertation advances optical tweezer platforms for neutral-atom quantum processors by addressing three interconnected bottlenecks: imaging survival, motional ground-state preparation, and narrow-line cooling, through experimental and theoretical work on single lithium and cesium atoms.For Li, the lightest stable alkali atom, this work demonstrates a per-image survival probability of 99.950(2)% and a state-detection fidelity of 99.97(2)% across 2000 consecutive 15 ms images, a record for any trapped neutral atom at the time of publication. This was achieved by applying Λ-enhanced gray-molasses (Λ-GM) cooling continuously on the D1 line while simultaneously imaging with the same beam, and represents the first demonstration of loading lithium into a tweezer directly from a MOT. To explain this performance, the dissertation develops a unified Lindblad master-equation formalism for laser cooling in a tightly confined harmonic trap, encompassing polarization-gradient, gray-molasses, EIT, Λ-GM, and single-photon sideband cooling within a single theoretical framework, with 1D simulations that correctly predict steady-state temperature, excited-state fraction, and cooling efficiency across these techniques.For133133Cs, the work exploits the forbidden electric-quadrupole transition 6S1/2→5D5/26S1/2→5D5/2 at 685 nm (Γ ≈ 2π × 117.6 kHz) to demonstrate background-free imaging and narrow-line sideband cooling for the first time in an alkali atom. By positioning the atom at the intensity node of a Laguerre-Gaussian vortex beam, the drive is enhanced while cascade fluorescence at 852 nm is optically isolated from the excitation light, enabling both high-fidelity background-free detection and single-photon sideband cooling to near the motional ground state.Beyond the core cooling and imaging results, the dissertation includes a comprehensive experimental techniques chapter (fiber coupling, AOM design, polarimetry, laser locking, optical pumping, and a Gaussian-process optimization framework), a chapter on quadrupole transition theory and orbital-angular-momentum selection rules, and a concluding survey of the competitive quantum computing landscape across neutral-atom, superconducting, trapped-ion, photonic, spin, and topological qubit platforms. Together, this work establishes the Cs and Li cooling/imaging toolbox as a foundation for future assembly of ultracold LiCs polar molecules in optical tweezer arrays.
Over the past decade, quantum information science has progressed from few-qubit demonstrations to experiments with hundreds of qubits. Neutral atom processors based on individual atoms trapped in arrays of optical tweezers have emerged as a leading candidate due to their inherent scalability and flexible connectivity. Advanced protocols like measurement-based state preparation and quantum error correction, however, require efficient crosstalk-free mid-circuit operations for the readout, reset, and replenishment of a subset of qubits. In typical single-species atom arrays, where all atoms are identical and on-resonance, such operations necessitate complex overheads from single-site addressing, coherent transport, or shielding techniques, to mitigate the qubit decoherence induced from photons scattered by neighboring atoms. To address this challenge of engineering scalable quantum architectures compatible with efficient control techniques, we introduce and implement the first dual-species atom array platform, and explore new dynamics inaccessible in single-species arrays. In this approach, two atomic species are addressed independently due to the spectral separation between their control wavelengths. We engineer two-dimensional arrays from individual rubidium (Rb) and cesium (Cs) atoms in up to 512 optical tweezers, and show that the two species can be independently trapped, cooled, and imaged with state-of-the-art performance metrics. Harnessing this intrinsic crosstalk-free control, we establish the key primitives of mid-circuit readout, real-time processing and feed-forward, and coherent mid-circuit reloading. By integrating these capabilities, we realize in-sequence, real-time correction of correlated phase errors via a spectator qubit protocol. Next, we excite atoms to Rydberg states in the Förster regime, accessing hitherto unobserved enhanced interspecies Rydberg interactions, and program them to implement the first interspecies CNOT gate. We combine this multispecies entanglement with mid-circuit readout to achieve quantum non-demolition measurement of a Rb-qubit using an auxiliary Cs-qubit, circumventing physical qubit transport. Finally, leveraging the two qubit modalities, we present the first experimental demonstration of quantum cellular automata in atom arrays using only global addressing, and prepare a 17-qubit Cs cluster state with Rb-mediated interactions. The dual-species platform and techniques established in this thesis pave the way toward measurement-based algorithms and real-time feedback control in large-scale quantum systems.
Scalable quantum computers and quantum networks require the combination of quantum processing nodes with efficient light-matter interfaces to distribute quantum information in local or long-distance quantum networks. Neutral-atom arrays have both been coupled to Rydberg states to enable high-fidelity quantum gates in universal processing architectures, and to optical cavities to realize interfaces to photons. However, combining these two capabilities and coupling atom arrays to highly excited Rydberg states in the mode of an optical cavity has been an outstanding challenge. Here we present a novel cavity-coupled Rydberg array that achieves this long-standing goal. We prepare, detect, and control individual atoms in a scalable optical tweezer array, couple them strongly to the optical mode of a high-finesse optical cavity and excite them in a controlled way to Rydberg states. We show that high-cooperativity coupling to an optical cavity -- demonstrated via the dispersive shift of the resonance of the cavity in presence of the atoms -- and strong Rydberg interactions -- demonstrated via the collective enhancement of Rydberg coupling in the atomic array -- can be achieved in our setup at the same spatial location. Our presented experimental platform opens the path to several new directions, including the realization of quantum network nodes, quantum simulation of long-range interacting, open quantum systems and photonic-state engineering leveraging high-fidelity Rydberg control.
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 × 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.