# Integrated $^{9}$Be$^{+}$ multi-qubit gate device for the ion-trap quantum computer

## TL;DR

This paper reports the successful experimental implementation of a high-fidelity two-qubit entangling gate in a $^9$Be$^+$ ion trap using microwave near-fields, advancing scalable quantum computing architectures.

## Contribution

It introduces a novel microwave conductor design embedded in a surface-electrode trap that enables high-fidelity multi-qubit gates in ion-trap quantum computers.

## Key findings

- Achieved 98.2% gate fidelity limited by technical imperfections.
- Designed a microwave conductor that produces a high magnetic field gradient.
- Demonstrated a scalable, self-contained module for entangling gates.

## Abstract

We demonstrate the experimental realization of a two-qubit M{\o}lmer-S{\o}rensen gate on a magnetic field-insensitive hyperfine transition in $^9$Be$^+$ ions using microwave-near fields emitted by a single microwave conductor embedded in a surface-electrode ion trap. The design of the conductor was optimized to produce a high oscillating magnetic field gradient at the ion position. The measured gate fidelity is determined to be $98.2\pm1.2\,\%$ and is limited by technical imperfections, as is confirmed by a comprehensive numerical error analysis. The conductor design can potentially simplify the implementation of multi-qubit gates and represents a self-contained, scalable module for entangling gates within the quantum CCD architecture for an ion-trap quantum computer.