Despite living in a complex, room temperature, solid-state environment, the spin of electrons bound to a nitrogen-vacancy (NV) defect in diamond can exist in a delicate quantum superposition over relatively long timescales. The delicacy of this state makes the system exquisitely sensitive to perturbations in magnetic field, temperature, or strain. As such, the NV is a good candidate for sensing applications, providing precise measurements with sub-nanometer spatial resolution. The robust quantum coherence of the NV spin also suggests applications in quantum information processing: if we can engineer entangled states of many NV spins, then computation may be carried out in the unbelievably voluminous Hilbert space of this system, instead of in the puny classical space of binary bits.
A central obstacle to realizing these types of spin-based applications is the need for fast, local, strong (effective) magnetic fields to address, control, and couple spins on nanosecond timescales, in scalable nanometer-scale devices, all at room temperature. I will present recent progress from our group, which suggests that we can overcome this obstacle using nanoscale vortices in ferromagnetic films [1,2]. The core of the vortex produces a point-dipole-like magnetic field, with strength approaching 1 T at the surface of the film. A coupled NV/vortex system provides a platform for sequentially addressing and controlling individual spins with nanometer-scale resolution, and on ~100 ns timescales, opening a pathway towards practical, integrated, spin-based devices.
 M.S. Wolf, R. Badea, J. Berezovsky, arXiv:1510.07073, 2015
 R. Badea, J. Berezovsky, arXiv:1510.07059, 2015.