Ultrasensitive diamond magnetometry using optimal dynamic decoupling

Magnetometry techniques based on nitrogen-vacancy (NV) defects in diamond have received much attention of late as a means to probe nanoscale magnetic environments. The sensitivity of a single NV magnetometer is primarily determined by the transverse spin-relaxation time, T-2. Current approaches to improving the sensitivity employ crystals with a high NV density at the cost of spatial resolution or extend T-2 via the manufacture of novel isotopically pure diamond crystals. We adopt a complementary approach in which optimal dynamic decoupling techniques extend coherence times out to the self-correlation time of the spin bath. This suggests single spin, room-temperature magnetometer sensitivities as low as 5 pT Hz-(1/2) may be possible with current technology.