Enhanced sensitivity in microscale high-field NMR via nuclear-spin locking with NV centers

Fuente: arXiv
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Auteurs principaux: Whaites, Oliver T., Oliván, Jaime García, Casanova, Jorge
Format: Preprint
Publié: 2025
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author Whaites, Oliver T.
Oliván, Jaime García
Casanova, Jorge
author_facet Whaites, Oliver T.
Oliván, Jaime García
Casanova, Jorge
contents Solid state defects such as nitrogen vacancy (NV) centers in diamond have been utilized for NMR sensing at ambient temperatures for samples at the nano-scale and up to the micro-scale. Similar to standard NMR, NV-sensitivities can be increased using tesla-valued magnetic fields to boost nuclear thermal polarization, while structural parameters, such as chemical shifts, are also enhanced. However, with standard microwave (MW) based sensing techniques, NV centers struggle to track fast megahertz Larmor frequencies encountered in high-field scenarios. Previous protocols have addressed this by mapping target NMR parameters to the signal amplitude rather than the frequency, using a mediating RF field. Although successful, protocol sensitivities are limited by the coherence time ($T_2^*$) of the NMR signal owing to the presence of stages where the sample magnetization freely evolves. In this work, we propose extending this coherence time, and consequently improving sensitivity, via amplitude encoding with weak nuclear spin locking instead of free evolution, thereby taking advantage of the longer sample coherence times ($T_{1ρ}$). We demonstrate this can enhance protocol sensitivities by $\gtrsim 4$ times.
format Preprint
id arxiv_https___arxiv_org_abs_2504_00887
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Enhanced sensitivity in microscale high-field NMR via nuclear-spin locking with NV centers
Whaites, Oliver T.
Oliván, Jaime García
Casanova, Jorge
Quantum Physics
Solid state defects such as nitrogen vacancy (NV) centers in diamond have been utilized for NMR sensing at ambient temperatures for samples at the nano-scale and up to the micro-scale. Similar to standard NMR, NV-sensitivities can be increased using tesla-valued magnetic fields to boost nuclear thermal polarization, while structural parameters, such as chemical shifts, are also enhanced. However, with standard microwave (MW) based sensing techniques, NV centers struggle to track fast megahertz Larmor frequencies encountered in high-field scenarios. Previous protocols have addressed this by mapping target NMR parameters to the signal amplitude rather than the frequency, using a mediating RF field. Although successful, protocol sensitivities are limited by the coherence time ($T_2^*$) of the NMR signal owing to the presence of stages where the sample magnetization freely evolves. In this work, we propose extending this coherence time, and consequently improving sensitivity, via amplitude encoding with weak nuclear spin locking instead of free evolution, thereby taking advantage of the longer sample coherence times ($T_{1ρ}$). We demonstrate this can enhance protocol sensitivities by $\gtrsim 4$ times.
title Enhanced sensitivity in microscale high-field NMR via nuclear-spin locking with NV centers
topic Quantum Physics
url https://arxiv.org/abs/2504.00887