Coherently controlling the motion of single atoms in optical tweezers would enable new applications in quantum information science. To demonstrate this, we first prepared atoms in their motional ground state using a species-agnostic cooling mechanism that converts motional excitations into erasures, errors with a known location. This cooling mechanism fundamentally outperforms idealized traditional sideband cooling, which we experimentally demonstrated. By coherently manipulating the resultant pure motional state, we performed mid-circuit readout and mid-circuit erasure detection through local shelving into motional superposition states. We lastly entangled the motion of two atoms in separate tweezers and generated hyperentanglement by preparing a simultaneous Bell state of motional and optical qubits, unlocking a large class of quantum operations with neutral atoms.
Coherently controlling the motion of single atoms in optical tweezers would enable new applications in quantum information science. To demonstrate this, we first prepared atoms in their motional ground state using a species-agnostic cooling mechanism that converts motional excitations into erasures, errors with a known location. This cooling mechanism fundamentally outperforms idealized traditional sideband cooling, which we experimentally demonstrated. By coherently manipulating the resultant pure motional state, we performed mid-circuit readout and mid-circuit erasure detection through local shelving into motional superposition states. We lastly entangled the motion of two atoms in separate tweezers and generated hyperentanglement by preparing a simultaneous Bell state of motional and optical qubits, unlocking a large class of quantum operations with neutral atoms.
Laser cooling of single atoms in optical tweezers is a prerequisite for neutral atom quantum computing and simulation. Resolved sideband cooling comprises a well-established method for efficient motional ground-state preparation, but typically requires careful cancellation of light shifts in so-called magic traps. Here, we study a novel laser cooling scheme which overcomes such constraints, and applies when the ground state of a narrow cooling transition is trapped stronger than the excited state. We demonstrate our scheme, which exploits sequential addressing of red sideband transitions via frequency chirping of the cooling light, at the example of 88Sr atoms and report ground-state populations compatible with recent experiments in magic tweezers. The scheme also induces light-assisted collisions, which are key to the assembly of large atom arrays. Our work enriches the toolbox for tweezer-based quantum technology, also enabling applications for tweezer-trapped molecules and ions that are incompatible with resolved sideband cooling conditions.
Schrödinger cat states - quantum superpositions of classically or macroscopically distinct states - constitute a powerful resource for quantum computing, enhanced metrology, and probing coherence on large scales. Encoding such states in the phase space of an oscillator requires a nonlinearity, typically inherited from an auxiliary degree of freedom such as atomic spin or a Josephson junction. Neutral atoms trapped in reconfigurable optical tweezer arrays - a leading platform for quantum science and computing - provide an intrinsic nonlinearity via the motion of a single atom in a tightly focused trap. However, this self-Kerr mechanism has not previously been exploited for cat-state generation, and remains largely unexplored as a resource for motional-state control. Here we realize Schrödinger cat states in the quantized motion of a single neutral atom trapped in an optical tweezer. By modulating the depth and position, we demonstrate parity control of both Kerr-cat and Fock states alongside tunable nonlinearity, establishing a spin- and species-independent framework for controlling motion. We further show that the cat-state encoding is intrinsically robust against trap-frequency fluctuations that otherwise limit the fidelity of direct Fock-state transitions. These results establish Kerr-based control of neutral-atom motion as a new paradigm for cat-state and bosonic-state engineering in optical tweezers, providing a route toward quantum-error-correcting codes such as grid states, and toward quantum-enhanced sensing with arrays of non-Gaussian states.
We report cooling of a single neutral atom to its three-dimensional vibrational ground state in an optical tweezer.After employing Raman sideband cooling for tens of milliseconds, we measure via sideband spectroscopy a three-dimensional ground-state occupation of about 90%.We further observe coherent control of the spin and motional state of the trapped atom.Our demonstration shows that an optical tweezer, formed simply by a tightly focused beam of light, creates sufficient confinement for efficient sideband cooling.This source of ground-state neutral atoms will be instrumental in numerous quantum simulation and logic applications that require a versatile platform for storing and manipulating ultracold single neutral atoms.For example, these results will improve current optical-tweezer experiments studying atom-photon coupling and Rydberg quantum logic gates, and could provide new opportunities such as rapid production of single dipolar molecules or quantum simulation in tweezer arrays.
We demonstrate full quantum state control of two species of single atoms using optical tweezers and assemble the atoms into a molecule.Our demonstration includes 3D ground-state cooling of a single atom (Cs) in an optical tweezer, transport by several microns with minimal heating, and merging with a single Na atom.Subsequently, both atoms occupy the simultaneous motional ground state with 61(4)% probability.This realizes a sample of exactly two cotrapped atoms near the phase-space-density limit of one, and allows for efficient stimulated-Raman transfer of a pair of atoms into a molecular bound state of the triplet electronic ground potential a 3 Σ þ .The results are key steps toward coherent creation of single ultracold molecules for future exploration of quantum simulation and quantum information processing.
We combine near-deterministic preparation of a single atom with Raman sideband cooling, to create a push-button mechanism to prepare a single atom in the motional ground state of tightly focused optical tweezers. In the two-dimensional (2D) radial plane, we achieve a large ground-state fidelity for the entire procedure (loading and cooling) of $\ensuremath{\sim}0.73$, while the ground-state occupancy is $\ensuremath{\sim}0.88$ for realizations with a single atom present. For 1D axial cooling, we attain a ground-state fraction of $\ensuremath{\sim}0.52$. The combined 3D cooling provides a ground-state population of $\ensuremath{\sim}0.11$. Our Raman sideband cooling variation is indifferent to magnetic field fluctuations, allowing widespread unshielded experimental implementations. Our work provides a pathway towards a range of coherent few-body experiments.
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.