Low-entropy preparation and fast single-qubit rotations for ¹⁷¹Yb nuclear spin qubits

In the past decade, neutral atoms in optical tweezer arrays have become a promising candidate for quantum information applications. Among systems being explored, alkaline-earth(-like) atoms have a number of desirable features, such as the presence of a nuclear-spin qubit resistant to many forms of decoherence, the possibility of trapping Rydberg states, and the existence of a long-lived clock transition for shelving coherent qubits. Here we demonstrate progress towards the realization of a high-performance quantum information system in ¹⁷¹Yb [1]. Through a novel scheme, a 10x10 tweezer array can be loaded with 92.73(8)% filling, greatly simplifying the task of realizing defect-free qubit arrays. With Raman sideband cooling, the atoms are prepared in the motional ground state with >80% fidelity in each of the three directions, which will be crucial to high-fidelity single- and two-qubit gate operations. Using a novel single-beam Raman technique, high-fidelity single-qubit rotations can be effected in several 100 ns, and using Ramsey spectroscopy, decoherence timescales are measured, T₂ = 8.1(7) s and T₂* = 3.7(4) s. These results demonstrate several of the powerful features of alkaline-earth tweezer systems for quantum information.

[1] Jenkins, A., Lis, J. W., Senoo, A., McGrew, W. F., & Kaufman, A. M. (2021). Ytterbium nuclear-spin qubits in an optical tweezer array. arXiV:2112.06732