# Optical spin locking of a solid-state qubit

## TL;DR

This paper demonstrates high-fidelity optical control of a solid-state spin qubit using programmable laser fields, enabling versatile quantum operations including spin locking and state transfer.

## Contribution

It introduces a method to perform full SU(2) spin control via optical means by imprinting microwave sequences onto laser fields, achieving over 98% fidelity.

## Key findings

- Achieved over 98% pi-rotation fidelity in optical spin control.
- Implemented multi-axis spin locking sequence.
- Demonstrated electron-nuclear Hartmann-Hahn resonances.

## Abstract

Quantum control of solid-state spin qubits typically involves pulses in the microwave domain, drawing from the well-developed toolbox of magnetic resonance spectroscopy. Driving a solid-state spin by optical means offers a high-speed alternative, which in the presence of limited spin coherence makes it the preferred approach for high-fidelity quantum control. Bringing the full versatility of magnetic spin resonance to the optical domain requires full phase and amplitude control of the optical fields. Here, we imprint a programmable microwave sequence onto a laser field and perform electron spin resonance in a semiconductor quantum dot via a two-photon Raman process. We show that this approach yields full SU(2) spin control with over 98% pi-rotation fidelity. We then demonstrate its versatility by implementing a particular multi-axis control sequence, known as spin locking. Combined with electron-nuclear Hartmann-Hahn resonances which we also report in this work, this sequence will enable efficient coherent transfer of a quantum state from the electron spin to the mesoscopic nuclear ensemble.