Neutral-atom quantum processors are a promising platform for scalable quantum computing. An obstacle to implementing deep quantum circuits is managing atom loss. Current approaches require at least an order of magnitude longer time than gate and measurement operations to replace lost atoms. In this work, we demonstrate fast, continuous atom reloading that leverages the metastable 171 Yb qubit. A continuously loaded reservoir near the computation zone enables on-demand atom extraction with tweezers up to 500 times per second. New, stochastically filled qubit arrays can be initialized 30 times per second when including single-atom preparation, nondestructive imaging, and initialization. Existing qubits in the metastable state are undisturbed by the reloading process. This work establishes a complete foundation for the implementation of fast, fully fault-tolerant quantum circuits with unlimited depth.
Neutral-atom quantum processors are a promising platform for scalable quantum computing. An obstacle to implementing deep quantum circuits is managing atom loss. Current approaches require at least an order of magnitude longer time than gate and measurement operations to replace lost atoms. In this work, we demonstrate fast, continuous atom reloading that leverages the metastable 171 Yb qubit. A continuously loaded reservoir near the computation zone enables on-demand atom extraction with tweezers up to 500 times per second. New, stochastically filled qubit arrays can be initialized 30 times per second when including single-atom preparation, nondestructive imaging, and initialization. Existing qubits in the metastable state are undisturbed by the reloading process. This work establishes a complete foundation for the implementation of fast, fully fault-tolerant quantum circuits with unlimited depth.
Neutral atoms are a promising platform for quantum science, enabling advances in areas ranging from quantum simulations 1−3 and computation 4−10 to metrology, atomic clocks 11−13 and quantum networking 14−16 . While atom losses typically limit these systems to a pulsed mode, continuous operation 17−22 could significantly enhance cycle rates, remove bottlenecks in metrology 23 , and enable deep-circuit quantum evolution through quantum error correction 24,25 . Here we demonstrate an experimental architecture for high-rate reloading and continuous operation of a large-scale atom array system while realizing coherent storage and manipulation of quantum information. Our approach utilizes a series of two optical lattice conveyor belts to transport atom reservoirs into the science region, where atoms are repeatedly extracted into optical tweezers without affecting the coherence of qubits stored nearby. Using a reloading rate of 300,000 atoms in tweezers per second, we create over 30,000 initialized qubits per second, which we leverage to assemble and maintain an array of over 3,000 atoms for more than two hours. Furthermore, we demonstrate persistent refilling of the array with atomic qubits in either a spin-polarized or a coherent superposition state while preserving the quantum state of stored qubits. Our results pave the way for realization of large-scale continuously operated atomic clocks, sensors, and fault-tolerant quantum computers.
A Dual Metastable-State Encoding Architecture for Quantum Processing with 171Yb Atom Arrays
Neutral-atom arrays combine scalable qubit registers, long coherence times, flexible optical control, and strong Rydberg-mediated entangling interactions, making them a promising platform for quantum information processing. However, physical error rates remain a challenge, and fault-tolerant quantum error correction (QEC) requires repeated mid-circuit measurement and reset of ancilla qubits without disturbing nearby data qubits. This requirement introduces significant control and architectural overhead, making qubit encoding an important architectural decision. Here, we propose a dual metastable-state qubit encoding for 171Yb atoms that utilizes two independent qubit subspaces in the (6s6p)3P0 and (6s6p)3P2 manifolds. The 3P0 manifold provides a long-coherence nuclear-spin (NS) qubit suitable for storage and arithmetic operations, while the 3P2 manifold provides a hyperfine-spin (HF) qubit, with ΔHF=2π×6.7GHz, that enables fast Raman operations and direct state-selective imaging. Coherent shelving between the two metastable manifolds connects the qubit subspaces, allowing operations to be assigned to spectrally distinct processor zones. We simulate single-qubit and two-qubit gate fidelities in 3P2, as well as coherent shelving between the HF and NS qubit subspaces. We incorporate these physical-level estimates into an architectural resource estimation and logical-level simulation. Our approach integrates mid-circuit measurements and fast qubit operations within a single-species platform, providing a versatile framework for future fault-tolerant quantum computing with neutral-atom qubits.
Assembling and maintaining large arrays of individually addressable atoms is a key requirement for continued scaling of neutral-atom-based quantum computers and simulators. In this work, we demonstrate a new paradigm for assembly of atomic arrays, based on a synergistic combination of optical tweezers and cavity-enhanced optical lattices, and the incremental filling of a target array from a repetitively filled reservoir. In this protocol, the tweezers provide microscopic rearrangement of atoms, while the cavity-enhanced lattices enable the creation of large numbers of optical traps with sufficient depth for rapid low-loss imaging of atoms. We apply this protocol to demonstrate near-deterministic filling (99% per-site occupancy) of 1225-site arrays of optical traps. Because the reservoir is repeatedly filled with fresh atoms, the array can be maintained in a filled state indefinitely. We anticipate that this protocol will be compatible with mid-circuit reloading of atoms into a quantum processor, which will be a key capability for running large-scale error-corrected quantum computations whose durations exceed the lifetime of a single atom in the system. Published by the American Physical Society 2024
Neutral-atom arrays have rapidly advanced to support thousands of qubits and execute high-fidelity logical operations. However, these processors remain severely throttled by their slowest fundamental operation: nondestructive qubit measurement, which requires milliseconds and fundamentally limits the system's clock rate. This bottleneck arises from both an inherent photon-budget dilemma---sufficient fluorescence for reliable state discrimination must be collected without excessive heating or loss---and frame-based imaging, which imposes one common exposure and decision latency on intrinsically independent, site-local measurements. Here, we overcome these limitations with a fast, nondestructive readout architecture based on real-time, site-resolved adaptive protection. By integrating continuous photon counting with a dynamic feedforward framework, we decode qubit states with sub-microsecond latency and instantly shield atoms from redundant scattering. Demonstrated in parallel across a 100-qubit reconfigurable atom array, with adaptive protection on a 25-site subarray, this dynamic decision protocol reduces the average probe time to just 15μs. Model-free benchmarking yields a discrimination infidelity of 4.1×10−5 and an atom loss of 2.1×10−4, simultaneously setting new performance records for atom arrays. Exploiting this capability, we operate repeated quantum circuits at an unprecedented 1.7 kHz clock rate with atoms reused over 120 consecutive rounds---nearly sevenfold higher than the previous record---and enter the sub-millisecond cycle regime for the first time. By removing nondestructive readout as the dominant cycle-time bottleneck, this work unlocks high-clock-rate mid-circuit syndrome extraction, paving the way for high-throughput, fault-tolerant quantum computation.
Quantum computers hold a promise to solve certain problems that are intractable to classical computers, offering a paradigm shift in fields ranging from cryptography to materials science. However, realizing this potential requires overcoming the challenge of scalability, which encompasses both spatial scalability – the capacity for large qubit registers, and temporal scalability – the capability to execute deep quantum circuits. This thesis describes the construction and experimental characterization of a new rubidium atom array quantum platform, which advances the scalability frontier of atomic quantum processors in both spatial and temporal domains. The platform achieves a record-scale ∼ 99%-filling-fraction array with more than 3,000 qubits, and is shown to operate continuously for more than 2 hours. These advances are enabled by a novel architecture that supports high-flux refilling of atomic qubits without decohering neighboring sites. Combined with other recent progress demonstrated in the field of neutral atom quantum information processing, this platform provides a viable pathway toward large-scale, fault-tolerant quantum processing capable of executing deep error-corrected circuits.
The realization of fault-tolerant quantum computation hinges on the ability to execute deep quantum circuits while maintaining gate fidelities consistently above error-correction thresholds. Although neutral-atom arrays have recently demonstrated high-fidelity two-qubit gates and early-stage logical quantum processors, sustaining such high performance across deep, repetitive circuits remains a formidable challenge due to cumulative motional heating and atom loss. Here we demonstrate a sustainable neutral-atom framework that overcomes these limitations by integrating a suite of hardware-efficient mid-circuit operations. We report a two-qubit controlled logic gate with a raw fidelity of 99.60(1)%, which is further increased to a fidelity of 99.81(1)% via non-destructive erasure detection. Crucially, by implementing in-circuit Raman sideband cooling and qubit re-initialization, we demonstrate that gate fidelities can be maintained at the ~99.8% level across multiple operational rounds without observable degradation. By actively managing the internal and motional entropy of the system mid-stream, our in-situ refreshable architecture provides a critical pathway for executing the repeated syndrome-extraction cycles required for large-scale, continuous quantum error correction.