Dynamical decoupling of a single-electron spin at room temperature

Here we report the increase of the coherence time T(2) of a single-electron spin at room temperature by using dynamical decoupling. We show that the Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence can prolong the T(2) of a single nitrogen-vacancy center in diamond up to 2.44 ms compared to the Hahn echo measurement where T(2) = 400 mu s. Moreover, by performing spin-locking experiments we demonstrate that with CPMG the maximum possible T(2) is reached. On the other hand, we do not observe a strong increase of the coherence time in nanodiamonds, possibly due to the short spin-lattice relaxation time T(1) = 100 mu s (compared to T(1) = 5.93 ms in bulk). An application for detecting low magnetic fields is demonstrated, where we show that the sensitivity using the CPMG method is improved by about a factor of 2 compared to the Hahn echo method.