One of the central challenges for a practical fault-tolerant quantum computer is scalability. A three-dimensional structure of optical tweezer arrays offers the potential for scaling up neutral atom processors. However, coherent operations, essential for quantum error correction, have yet to be explored for this platform. Here, we demonstrate plane-by-plane initialization of nuclear spin qubits of Yb 171 atoms in a three-dimensional atom array and plane-dependent coherent temporal evolution of qubits, as well as plane-selective qubit manipulation by exploiting the plane-selective excitation of the atoms from the S 0 1 to the P 2 3 state. This plane-selective manipulation technique paves the way for quantum computing and quantum simulation in three-dimensional multilayer architectures.
One of the central challenges for a practical fault-tolerant quantum computer is scalability. A three-dimensional structure of optical tweezer arrays offers the potential for scaling up neutral atom processors. However, coherent operations, essential for quantum error correction, have yet to be explored for this platform. Here, we demonstrate plane-by-plane initialization of nuclear spin qubits of Yb 171 atoms in a three-dimensional atom array and plane-dependent coherent temporal evolution of qubits, as well as plane-selective qubit manipulation by exploiting the plane-selective excitation of the atoms from the S 0 1 to the P 2 3 state. This plane-selective manipulation technique paves the way for quantum computing and quantum simulation in three-dimensional multilayer architectures.
We report on the realization of a fast, scalable, and high-fidelity qubit architecture, based on 171 Yb atoms in an optical tweezer array.We demonstrate several attractive properties of this atom for its use as a building block of a quantum information processing platform.Its nuclear spin of 1=2 serves as a long-lived and coherent two-level system, while its rich, alkaline-earth-like electronic structure allows for low-entropy preparation, fast qubit control, and high-fidelity readout.We present a near-deterministic loading protocol, which allows us to fill a 10 × 10 tweezer array with 92.73(8)% efficiency and a single tweezer with 96.0(1.4)%efficiency.In the future, this loading protocol will enable efficient and uniform loading of target arrays with high probability, an essential step in quantum simulation and information applications.Employing a robust optical approach, we perform submicrosecond qubit rotations and characterize their fidelity through randomized benchmarking, yielding 5.2ð5Þ × 10 -3 error per Clifford gate.For quantum memory applications, we measure the coherence of our qubits with T Ã 2 ¼ 3.7ð4Þ s and T 2 ¼ 7.9ð4Þ s, many orders of magnitude longer than our qubit rotation pulses.We measure spin depolarization times on the order of tens of seconds and find that this can be increased to the 100 s scale through the application of a several-gauss magnetic field.Finally, we use 3D Raman-sideband cooling to bring the atoms near their motional ground state, which will be central to future implementations of two-qubit gates that benefit from low motional entropy.
While data qubits with a long coherence time are essential for the storage of quantum information, ancilla qubits are pivotal in quantum error correction (QEC) for fault-tolerant quantum computing. The recent development of optical tweezer arrays, such as the preparation of large-scale qubit arrays and high-fidelity gate operations, offers the potential for realizing QEC protocols, and one of the important next challenges is to control and detect ancilla qubits while minimizing atom loss and crosstalk. Here, we present the realization of a hybrid system consisting of a dual-isotope ytterbium (Yb) atom array, in which we can utilize a nuclear spin qubit of fermionic Yb 171 as a data qubit and an optical clock qubit of bosonic Yb 174 as an ancilla qubit with a capacity of nondestructive qubit readout. We evaluate the crosstalk between qubits regarding the impact on the coherence of the nuclear spin qubits from the imaging light for Yb 174 . For the Hahn-echo sequence with a 399 nm probe and 556 nm cooling beams for Yb 174 , we observe 99.1(1.8)% coherence retained under 20 ms exposure, yielding a discrimination fidelity of 0.9992 and a survival probability of 0.988. The Ramsey sequence with a 556 nm probe beam shows negligible influence on the coherence, suggesting the potential future improvement of low crosstalk measurements. This result highlights the potential of the hybrid-Yb atom array for midcircuit measurements for ancilla-qubit-based QEC protocols. Published by the American Physical Society 2024
Optical tweezer arrays of neutral atoms have been demonstrated in recent years to be a useful platform for quantum simulation, computation, and metrology. Realizing the full potential of these applications requires increasing qubit numbers while simultaneously maintaining high-fidelity control, which has proved a major challenge across quantum platforms. To date, quantum science experiments have typically been operated with at most hundreds of qubits. In this thesis, we review the relevant physics of the optical tweezer array architecture and present the technical advances involved in scaling the platform to 6,100 atomic qubits. In tandem with scalability, we demonstrate robust vacuum design, state-of-the-art coherence times, and high single-qubit gate fidelities. To capitalize on the intrinsic connectivity of the architecture at large scale, we investigate long-distance coherent atom transport and briefly describe progress towards two-qubit gate implementation. Finally, we discuss the prospects for scaling the optical tweezer array platform further by an order of magnitude.
Abstract A great challenge in current quantum science and technology research is to realize artificial systems of a large number of individually controlled quantum bits for applications in quantum computing and quantum simulation. Many experimental platforms are being explored, including solid-state systems, such as superconducting circuits1 or quantum dots2, and atomic, molecular and optical systems, such as photons, trapped ions or neutral atoms3–7. The latter offer inherently identical qubits that are well decoupled from the environment and could provide synthetic structures scalable to hundreds of qubits or more8. Quantum-gas microscopes9 allow the realization of two-dimensional regular lattices of hundreds of atoms, and large, fully loaded arrays of about 50 microtraps (or ‘optical tweezers’) with individual control are already available in one10 and two11 dimensions. Ultimately, however, accessing the third dimension while keeping single-atom control will be required, both for scaling to large numbers and for extending the range of models amenable to quantum simulation. Here we report the assembly of defect-free, arbitrarily shaped three-dimensional arrays, containing up to 72 single atoms. We use holographic methods and fast, programmable moving tweezers to arrange—atom by atom and plane by plane—initially disordered arrays into target structures of almost any geometry. These results present the prospect of quantum simulation with tens of qubits arbitrarily arranged in space and show that realizing systems of hundreds of individually controlled qubits is within reach using current technology.
Arrays of single atoms trapped in optical tweezers are increasingly recognized as a promising platform for scalable quantum computing. In both the fault-tolerant and NISQ eras, the ability to individually control qubits is essential for the efficient execution of quantum circuits. Time-division multiplexed control schemes based on atom shuttling or beam scanning have been employed to build programmable neutral atom quantum processors, but achieving high-rate, highly parallel gate operations remains a challenge. Here, we propose a fiber array architecture for atom quantum computing capable of fully independent control of individual atoms. The trapping and addressing lasers for each individual atom are emitted from the same optical waveguide, enabling robust control through common-mode suppression of beam pointing noise. Using a fiber array, we experimentally demonstrate the trapping and independent control of ten single atoms in two-dimensional optical tweezers, achieving individually addressed single-qubit gates with an average fidelity of 0.9966(3). More significantly, we perform simultaneous arbitrary single-qubit gates on four randomly selected qubits, resulting in an average fidelity of 0.9961(4). Our work paves the way for time-efficient execution of quantum algorithms on neutral atom 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.