Quantum sensing of a coherent single spin excitation in a nuclear ensemble

TL;DR

This paper demonstrates the detection of a single nuclear spin excitation in an ensemble using an electron spin qubit, achieving high precision and observing coherent quantum dynamics, advancing quantum sensing capabilities.

Contribution

It introduces a method to sense single nuclear spin excitations with high precision using an electron spin qubit in a semiconductor quantum dot, enabling detailed quantum state monitoring.

Findings

Single-magnon detection with 1.9-ppm precision

Identification of multiple nuclear species and polarity modes

Observation of coherent nuclear magnon dynamics

Abstract

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.