The measurement of single quanta in a collection of coherently interacting objects is transformative in the investigations of emergent quantum phenomena. An isolated nuclear-spin ensemble is a remarkable platform owing to its coherence, but detecting its single spin excitations has remained elusive. Here, we use an electron spin qubit in a semiconductor quantum dot to sense a single nuclear-spin excitation (a nuclear magnon) with 1.9-ppm precision via the 200-kHz hyperfine shift on the 28-GHz qubit frequency. We demonstrate this single-magnon precision across multiple modes identified by nuclear species and polarity. Finally, we monitor the coherent dynamics of a nuclear magnon and the emergence of quantum correlations competing against decoherence. A direct extension of this work is to probe engineered quantum states of the ensemble including long-lived memory states.
@article{arxiv.2008.09541,
title = {Quantum sensing of a coherent single spin excitation in a nuclear ensemble},
author = {Daniel M. Jackson and Dorian A. Gangloff and Jonathan H. Bodey and Leon Zaporski and Clara Bachorz and Edmund Clarke and Maxime Hugues and Claire Le Gall and Mete Atatüre},
journal= {arXiv preprint arXiv:2008.09541},
year = {2021}
}