Parallel implementation of high-fidelity multi-qubit gates with neutral atoms (1908.06101v2)

Abstract: We report the implementation of universal two- and three-qubit entangling gates on neutral atom qubits encoded in long-lived hyperfine ground states. The gates are mediated by excitation to strongly interacting Rydberg states, and are implemented in parallel on several clusters of atoms in a one-dimensional array of optical tweezers. Specifically, we realize the controlled-phase gate, enacted by a novel, fast protocol involving only global coupling of two qubits to Rydberg states. We benchmark this operation by preparing Bell states with fidelity $\mathcal{F} \ge 95.0(2)\%$, and extract gate fidelity $\ge 97.4(3)\%,$ averaged across five atom pairs. In addition, we report a proof-of-principle implementation of the three-qubit Toffoli gate, in which two control atoms simultaneously constrain the behavior of one target atom. These experiments demonstrate key ingredients for high-fidelity quantum information processing in a scalable neutral atom platform.

• The paper presents a novel protocol using two global laser pulses to implement CZ gates with Bell state fidelities exceeding 95%.
• It leverages Rydberg blockade in one-dimensional optical tweezer arrays to execute simultaneous two- and three-qubit operations.
• The study offers practical advances for scalable neutral atom quantum computing, achieving gate fidelities up to 97.4%.

Parallel Implementation of High-Fidelity Multi-Qubit Gates with Neutral Atoms

The paper presents a significant stride in the implementation of universal entangling gates in the field of neutral atom quantum computing. The paper demonstrates the use of neutral atoms, which are attractive due to their scalability and coherence properties, in implementing both two-qubit and three-qubit gates. The authors focus on qubits encoded in long-lived hyperfine ground states, utilizing Rydberg state interactions to mediate entanglement, which is executed in parallel across multiple clusters of atoms.

The core achievement detailed in the paper is the realization of a controlled-phase (CZ) gate through a novel protocol that employs only two global laser pulses to drive qubits to Rydberg states within the blockade regime. This approach contrasts with traditional methods requiring sequential local pulses and offers efficiency both in time and operational overhead. The benchmark results show the successful preparation of Bell states with fidelities exceeding 95.0%, and gate fidelities reaching 97.4%, across multiple atom pairs, demonstrating competitiveness with leading quantum platforms like trapped ions and superconducting circuits.

The paper further extends its findings with a proof-of-principle implementation of a three-qubit Toffoli gate, where Rydberg blockade is again employed to control interactions among three atoms. This result highlights the robustness of Rydberg interactions for multi-qubit operations involving more than two qubits, indicating a path forward for scalable quantum information processing.

The experiments are performed using optical tweezers forming one-dimensional atom arrays, with precise single-atom initialization and readout. The authors employ global and local laser fields to manipulate qubits, relying on resonance tuning to achieve desired multi-qubit dynamics. The novel CZ gate protocol leverages coherent atomic evolutions on Bloch spheres to impart desired dynamical phases, and the insights gained from this work set the stage for further exploration of more complex quantum operations and algorithms.

The implications of this research extend to both practical quantum computing applications and theoretical advancements. Practically, the reported techniques could facilitate the development of neutral atom quantum processors capable of supporting larger-scale quantum computations and simulations. The flexibility and control demonstrated in multi-qubit operations suggest the potential for these methods to underpin future quantum error correction and fault-tolerant protocols essential for robust quantum computing.

Theoretically, the findings invite future work into optimizing and scaling these atomic interactions under different experimental conditions and configurations, including exploring two-dimensional or three-dimensional atom arrangements for enhanced connectivity and coherence. The advances shown in this paper promise to influence ongoing research and development focused on building viable quantum processors, offering a scalable pathway that leverages the unique strengths of neutral atom platforms. Ultimately, this paper contributes a substantial body of work that enriches the state of quantum control in Rydberg systems, broadening the possibilities for neutral atom-based quantum information processing.