Extended Data Fig. 9: Determining the optimal inter-pulse delay for state storage and 1,024 inversion pulses.

We initialize a superposition state on the NV-centre electron spin, preserve it via dynamical decoupling and finally perform optical readout after another π/2 pulse. We probe the coherence of the NV centre by varying the inter-pulse delay t in steps of the Larmor period 1/ν_L ≈ 2.25 μs and shifting the delay in steps of 4 ns for a total of five data points per Larmor period (grey). For each multiple of the Larmor period we pick the best (the most preserving) inter-pulse delay (blue). We determine the optimal delay t by selecting an inter-pulse delay that provides sufficient state preservation (about 100 ms) for a moderate number of pulses (red data point and inset text). Left, node A; right, node B. Error bars are 1 s.d.