# Quantum Interface of an Electron and a Nuclear Ensemble

## TL;DR

This paper demonstrates a coherent interface between a single electron and a nuclear spin ensemble in a quantum dot, enabling quantum memory and state engineering in a solid-state platform.

## Contribution

It introduces an all-optical method to coherently control and rotate nuclear spin excitations linked to a single electron in a quantum dot, advancing quantum memory technology.

## Key findings

- Nuclear ensemble cooled to the nuclear sideband-resolved regime.
- All-optical access to electronic-nuclear spin transitions.
- Coherent optical rotations of nuclear magnons achieved.

## Abstract

Coherent excitation of an ensemble of quantum objects underpins quantum many-body phenomena, and offers the opportunity to realize a quantum memory to store information from a qubit. Thus far, a deterministic and coherent interface between a single quantum system, e.g. a qubit, and such an ensemble has remained elusive. We first use an electron to cool the mesoscopic nuclear-spin ensemble of a semiconductor quantum dot to the nuclear sideband-resolved regime. We then implement an all-optical approach to access these individual quantized electronic-nuclear spin transitions. Finally, we perform coherent optical rotations of a single collective nuclear spin excitation corresponding to a spin wave called a nuclear magnon. These results constitute the building blocks of a dedicated local memory per quantum-dot spin qubit and promise a solid-state platform for quantum-state engineering of isolated many-body systems.