Scalable entangling gates on ion qubits via structured light addressing

TL;DR

This paper introduces a scalable trapped-ion quantum processor that uses structured light to perform high-fidelity two-qubit gates in larger ion chains without complex pulse shaping, advancing practical quantum computing.

Contribution

It presents a novel individual-addressing system with steerable Hermite-Gaussian beams that enables selective entanglement in larger ion chains, reducing control complexity.

Findings

Achieved two-qubit gate fidelities around 0.97 in chains up to six ions.

Demonstrated addressable gates without complex pulse shaping techniques.

Reduced control overhead while maintaining scalability.

Abstract

A central challenge in developing practical quantum processors is maintaining low control complexity while scaling to large numbers of qubits. Trapped-ion systems excel in small-scale operations and support rapid qubit scaling via long-chain architectures. However, their performance in larger systems is hindered by spectral crowding in radial motional modes, a problem that forces reliance on intricate pulse-shaping techniques to maintain gate fidelities. Here, we overcome this challenge by developing a novel trapped-ion processor with an individual-addressing system that generates steerable Hermite-Gaussian beam arrays. The transverse gradient of these beams couples qubits selectively to sparse axial motional modes, enabling to isolate a single mode as entanglement mediator. Leveraging this capability, we demonstrate addressable two-qubit entangling gates in chains up to six ions with fidelities consistently around 0.97, achieved without complex pulse shaping. Our method significantly reduces control overhead while preserving scalability, providing a crucial advance toward practical large-scale trapped-ion quantum computing.