EPJ Quantum Technol. (2016) 3: 1
https://doi.org/10.1140/epjqt/s40507-015-0039-8

Research

Dynamical nuclear polarization using multi-colour control of color centers in diamond

¹ School of Physics, Huazhong University of Science and Technology, Wuhan, 430074, China
² Center for Quantum Optical Science, Huazhong University of Science and Technology, Wuhan, 430074, China
³ Institut für Theoretische Physik, Universität Ulm, Albert-Einstein Allee 11, Ulm, 89069, Germany
⁴ Center for Integrated Quantum Science and Technology, Universität Ulm, Ulm, 89069, Germany

^* e-mail: jianmingcai@hust.edu.cn

Received: 27 April 2015
Accepted: 17 December 2015
Published online: 13 January 2016

Abstract

Dynamical nuclear polarization (DNP) transfers the polarization of electron spins at cryogenic temperatures to achieve strong nuclear polarization for applications in nuclear magnetic resonance. Recently introduced approaches employ optical pumping of nitrogen-vacancy (NV) centers in diamond to achieve DNP even at ambient temperatures. In such schemes microwave radiation is used to establish a Hartmann-Hahn condition between the NV electron spin and proximal nuclear spins to facilitate polarization transfer. For a single monochromatic microwave driving field, the Hartmann-Hahn condition cannot be satisfied for an ensemble of NV centers due to inhomogeneous broadening and reduces significantly the overall efficiency of dynamical nuclear polarization using an ensemble of NV centers. Here, we adopt generalized Hartmann-Hahn type dynamical nuclear polarization schemes by applying microwave driving fields with (multiple) time-modulated frequencies. We show that it is possible to enhance the effective coupling between an ensemble of NV center spins with inhomogeneous broadening and nuclear spins, thereby improving significantly the overall efficiency of dynamical nuclear polarization. This approach can also be used to achieve dynamical nuclear polarization of an ensemble of nuclei with a distribution of Larmor frequencies, which would be helpful in magnetic resonance spectroscopy using a single NV spin sensor.