Nuclear spins are a natural choice for applications requiring long relaxation times due to their immunity to unwanted perturbations from the environment.
Among the many applications are magnetic resonance-based bio-sensing and quantum computing. However, thermal polarization of nuclear spins, determined by the Boltzmann factor, is particularly low, especially at room temperature. This limitation results in poor sensitivities, requiring methods that achieve an enhancement over thermal polarization. In this work we report on strongly enhanced bulk nuclear polarization of 13C in diamond at room-temperature. We implement two polarization techniques based on the transfer of optically pumped electron spin polarization of nitrogen-vacancy color centers, to the nuclear spins. The first method relies on anti-crossing between the electronic energy levels to facilitate the electron- nucleus spin polarization transfer . The second method employs resonant microwave excitation to directly transfer the spin polarization .
The latter approach is compatible with a broad range of magnetic field strengths and field orientations with respect to the diamond lattice. Nuclear magnetic resonance 13C-detected experiments demonstrate that the local hyperpolarization is then extended throughout the nuclear bulk ensemble. These methods open new perspectives on the ensemble and nanoscale applications of these states on NMR/MRI and quantum information processing.
 R. Fischer, C. Bretschneider, P. London, D. Budker, D. Gershoni, L.Frydman, Phys. Rev. Lett 111, 057601 (2013).
 G. A. Alvarez, C. Bretschneider, R. Fischer, P. London, H. Kanda, J.Isoya, S. Onoda, D. Gershoni, L. Frydman, arXiv:1412.8635.