Low-crosstalk optical addressing system for atomic qubits based on multiple objectives and acousto-optic deflectors

Large-scale programmable trapped ion hardware, featuring high gate fidelity and long coherence times, is promising for realizing a practical fault-tolerant quantum computer. However, individual addressing (IA) methods, which are useful for implementing programmable gates in near-term quantum devices, can lead to undesired errors between the target ions and neighboring ions. In this work, we present a low-crosstalk optical addressing system based on multiple optical objectives and acousto-optic deflectors (AODs) with a symmetrical configuration. Two counterpropagating Raman operation beams are both tightly focused, generating an overlapping spot with a waist radius of approximately 1 mu m, to address the target ion. As a result, IA crosstalk, characterized by Rabi-rate crosstalk on the spectator ion, is measured to be 1.19(5) x 10-3, with the two ions separated by approximately 5.5 mu m. This low-crosstalk optical addressing system holds promise for high-fidelity entangling operations, and the symmetrically configured AODs in our method can be readily extended to two dimensions to address a two-dimensional ion crystal.