# Closed-loop control of a GaAs-based singlet-triplet spin qubit with 99.5% gate fidelity and low leakage

## TL;DR

This paper demonstrates high-fidelity, low-leakage exchange-based single-qubit gates in GaAs singlet-triplet spin qubits using closed-loop control, achieving 99.5% fidelity and enabling microwave-free control in GaAs.

## Contribution

It introduces a method for high-fidelity exchange-based control of GaAs spin qubits with closed-loop tuning, surpassing previous fidelities and reducing leakage.

## Key findings

- Achieved 99.50% randomized benchmarking fidelity.
- Reduced leakage rate to 0.13%.
- Enabled microwave-free control of singlet-triplet qubits.

## Abstract

Semiconductor spin qubits have recently seen major advances in coherence time and control fidelities, leading to a single-qubit performance that is on par with other leading qubit platforms. Most of this progress is based on microwave control of single spins in devices made of isotopically purified silicon. For controlling spins, the exchange interaction is an additional key ingredient which poses new challenges for high-fidelity control. Here, we demonstrate exchange-based single-qubit gates of two-electron spin qubits in GaAs double quantum dots. Using careful pulse optimization and closed-loop tuning, we achieve a randomized benchmarking fidelity of $(99.50 \pm 0.04)\%$ and a leakage rate of $0.13\%$ out of the computational subspace. These results open new perspectives for microwave-free control of singlet-triplet qubits in GaAs and other materials.