Dressed-state Hamiltonian engineering in a strongly interacting solid-state spin ensemble

TL;DR

This paper introduces a novel dressed-state Hamiltonian engineering method for NV center spin ensembles that enhances coherence and sensitivity, surpassing Floquet engineering limitations for quantum sensing applications.

Contribution

The authors develop a direct native interaction tuning technique using dressed-state encoding, significantly improving coherence and sensitivity in NV center ensembles.

Findings

3.2× enhancement of the coherence parameter $JT_2$

2.6× (8.3 dB) improved AC magnetometry sensitivity

Experimental probing of spin transport at extended times

Abstract

In quantum science applications, ranging from many-body physics to quantum metrology, dipolar interactions in spin ensembles are controlled via Floquet engineering. However, this technique typically reduces the interaction strength between spins, and effectively weakens the coupling to a target sensing field, limiting the metrological sensitivity. In this work, we develop and demonstrate a method for direct tuning of the native interaction in an ensemble of nitrogen-vacancy (NV) centers in diamond. Our approach utilizes dressed-state qubit encoding under a magnetic field perpendicular to the crystal lattice orientation. This method leads to a $3.2\times$ enhancement of the dimensionless coherence parameter $JT_2$ compared to state-of-the-art Floquet engineering, and a $2.6\times$ ($8.3~$dB) enhanced sensitivity in AC magnetometry. Utilizing the extended coherence we experimentally probe spin transport at intermediate to late times. Our results provide a powerful Hamiltonian engineering tool for future studies with NV ensembles and other interacting higher-spin ($S>\frac{1}{2}$) systems.