Low-Crosstalk, Silicon-Fabricated Optical Waveguides for Laser Delivery to Matter Qubits

TL;DR

This paper presents a silicon nitride optical waveguide chip that significantly reduces crosstalk for laser delivery to matter qubits, enabling scalable quantum information processing with trapped ions.

Contribution

The authors developed a CMOS-fabricated silicon nitride waveguide with integrated crosstalk mitigation, achieving over 50 dB reduction in optical field leakage between adjacent outputs.

Findings

Achieved at least 50.8 dB crosstalk reduction at 650 nm.

Demonstrated laser cooling of eight barium ions using the waveguide outputs.

Validated waveguide performance with fluorescence imaging of ions.

Abstract

Reliable control of quantum information in matter-based qubits requires precisely applied external fields, and unaccounted for spatial cross-talk of these fields between adjacent qubits leads to loss of fidelity. We report a CMOS foundry-produced, micro-fabricated silicon nitride (Si3N4) optical waveguide for addressing a chain of eight, unequally-spaced trapped barium ions with crosstalk compatible with scalable quantum information processing. The crosstalk mitigation techniques incorporated into the chip design result in a reduction of the measured optical field by at least 50.8(1.3) dB between adjacent waveguide outputs near 650 nm and similar behavior for devices designed for 493 nm and 585 nm. The waveguide outputs near 650 nm, along with a global laser near 493 nm were used to laser-cool a chain of eight barium-138 ions, and a camera imaged the resulting fluorescence at 493 nm.