Optically detected nuclear magnetic resonance of carbon-13 in bulk diamond

TL;DR

This paper demonstrates a technique for optically polarized and read out large ensembles of 13C nuclear spins in diamond, achieving high sensitivity and coherence times suitable for quantum sensing and fundamental physics applications.

Contribution

It introduces a method using Landau-Zener transitions for bidirectional polarization transfer between NV electron spins and 13C nuclear spins in diamond.

Findings

Achieved optical polarization and readout of ~10^{16} nuclear spins.

Observed nuclear spin dephasing times T2*~2 ms, limited by NV electron spin relaxation.

Demonstrated high-contrast Ramsey spectroscopy at 8-20 mT magnetic fields.

Abstract

Precision measurements based on optically detected nuclear magnetic resonance offer exquisite sensitivity to absolute shifts in spin transition frequencies, with potential applications in fundamental physics experiments and inertial sensing. We investigate 13C nuclear spins in diamond as a candidate system for solid-state implementations, which hold the promise for high-fidelity readout of large numbers of coherent nuclear spins in millitesla or lower magnetic fields. We demonstrate a technique that allows for both optical polarization and readout of large ensembles of ~10^{16} polarized nuclear spins. Our method takes advantage of state-selective Landau-Zener transitions under microwave frequency sweeping, which bidirectionally transfer spin polarization between Nitrogen-Vacancy (NV) electron spins and remote 13C nuclear spins. Using natural isotopic abundance diamonds with nitrogen densities of ~0.5-10 ppm, we perform optically-detected 13C Ramsey spectroscopy and realize a nuclear-spin-dependent fluorescence contrast exceeding 0.5% peak-to-peak. We observe nuclear spin dephasing times T2*~2 ms that only modestly improve with homonuclear dipolar decoupling, indicating that they are limited by the longitudinal spin relaxation of nearby NV electron spins. We study the magnetic field dependence of the optical readout and find comparable contrast and dephasing times for magnetic fields in the range 8-20 mT. Our method can be interpreted as a type of repetitive readout, where each NV center optically reads out the spin state of ~100 nuclei before nuclear spins depolarize.