High-sensitivity diamond magnetometer with nanoscale resolution
  We present a novel approach to the detection of weak magnetic fields that takes advantage of recently developed techniques for the coherent control of solid-state electron spin quantum bits. Specifically, we investigate a magnetic sensor based on Nitrogen-Vacancy centers in room-temperature diamond. We discuss two important applications of this technique: a nanoscale magnetometer that could potentially detect precession of single nuclear spins and an optical magnetic field imager combining spatial resolution ranging from micrometers to millimeters with a sensitivity approaching few femtotesla/Hz$^{1/2}$. 
J. M. Taylor, P. Cappellaro, L. Childress, L. Jiang, D.Budker, P. R.   Hemmer, A.Yacoby, R. Walsworth, M. D. Lukin