High Magnetic Field Quantum Sensing via Hyperpolarized Nuclei

In the quest towards high-resolution quantum sensors for applications in sub-micronscale NMR, the high-field

regime is advantageous since it naturally enables chemical shift discrimination and allows higher analyte polarization.

Here we propose and demonstrate a high-field (7T) quantum sensor constructed from hyperpolarized

13C nuclear spins in diamond. The 13C nuclei are initialized via Nitrogen-Vacancy (NV) centers and protected

along a transverse Bloch sphere axis for minute-long periods. When exposed to a time-varying (AC) magnetic

field, they undergo secondary precessions that contain a direct imprint of its frequency. We demonstrate that

high sensitivity and resolution is feasible by harnessing the long rotating frame 13C sensor lifetimes T2'>20 s, over

106 greater than their NV center counterparts, and their ability to be continuously interrogated. For quantum

sensing at 7 T, we demonstrate spectral resolution better than 70 mHz (corresponding to a precision 1 ppm) and

sensitivity better than 20 nT/vHz for a single crystal sample. We discuss the advantages of nuclear magnetometers over conventional NV center

sensors, including deployability in randomly-oriented diamond particles, in optically scattering media, and in a

wide range of bias field environments (1-20 T). Fundamentally, our technique with densely-packed 13C nuclei

demonstrates a new approach for quantum sensing in the “coupled-sensor” limit. This work points to intriguing

opportunities for “targeted” microscale NMR chemical sensors constructed from hyperpolarized

nanodiamonds and portends applications of dynamic nuclear polarization (DNP) in quantum sensing.