Figure 1. Characterization of the noises in experiment.

(a) Schematic atomic and energy levels of the NV centre. Laser pulses are used for state initialization and readout. Microwave pulses (MW) are used for coherent control of the electron spin. Radiofrequency pulses (RF) are used for manipulating the nuclear spin. (b), Result of the Ramsey experiment (inset, pulse sequence) for the electron spin. The solid black line in the left panel is fit to the experimental data (red circles) with P₀(δ₀), which is the probability density distribution of δ₀ depicted in the right panel. The decay time of FID is measured to be . (c), Results of the nutation experiment (inset, pulse sequence) for the electron spin. The stepped MW pulse length is set to be 810 ns. The decay time of the nutation is . The solid black line in the left panel is fit to the experimental results (olive diamonds) with P₁(δ₁), the probability density distribution of δ₁ depicted in the right panel. The error bars on the data points are the standard deviations from the mean.