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arXiv · 2606.10452

Floquet analysis of coherence in periodically driven diamond NV ensemble systems

Cuong M. Nguyen·Uijin Ko·Seong-Joo Lee·Hyeonsu Kim·Hosung Seo·Sangwon Oh
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Abstract

High-density nitrogen-vacancy (NV) ensembles are promising platforms for solid-state quantum sensing, but their performance is limited by dipolar interactions and inhomogeneous dephasing. Periodic decoupling sequences such as Waugh-Huber-Haeberlen (WAHUHA) can extend the observed stroboscopic decay time. However, it remains unclear that a longer effective dephasing time yield improved magnetic-field sensitivity. Here, we show that WAHUHA control increases the effective inhomogeneous dephasing time of a dense NV ensemble from $T_2^\ast$ of 0.9 ${\mu}$s to $T_{2,eff}^\ast$ of 31 ${\mu}$s, while producing little improvement in dc magnetic-field sensitivity. Using detuning-resolved stroboscopic spectroscopy and finite-pulse Floquet analysis, we show that the long-lived signal arises from phase wrapping and quasi-energy branch folding of the one-cycle unitary. These effects reshape the stroboscopic spectrum and suppress the detuning-to-phase transduction slope, $d\Phi/d\Delta$, which governs the dc magnetic-field response. Our results demonstrate that, under periodic driving, an extended effective dephasing time does not necessarily translate into enhanced dc sensitivity and establish finite-pulse Floquet analysis as a practical framework for evaluating coherence in spin ensembles.

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Cuong M. Nguyen, Uijin Ko, Seong-Joo Lee, Hyeonsu Kim, Hosung Seo, Sangwon Oh. 2026-06-09. Floquet analysis of coherence in periodically driven diamond NV ensemble systems. https://arxiv.org/abs/2606.10452

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