Fig. 3: Characterization of the NV center electron spin qubit.
a Statistics of detected photons for our spin qubit readout after spin initialization in the ms = ± 1 or ms = 0 state. The inset presents the corresponding readout fidelities depending on the number of short excitation pulses used. For the experiments, 200 short readout pulses are used, which leads to fidelities of F±1 = 98.4%, F0 = 10.3% and Favg = 54.4% for the shown calibration with 500 × 103 repetitions. b Coherent Rabi oscillations with a fit (solid line) showing a Rabi frequency of Ω = (10.73 ± 0.02) MHz. The error bars are within the dot size. c Ramsey measurement with an artificial detuning of 50 MHz. The inset shows the used microwave pulse sequence, where a delay time-dependent phase is applied to the second pulse to generate the artificial detuning. The fit (solid line) captures a beating signature of (2.68 ± 0.05) MHz which is attributed to the coupled nitrogen nuclear spin and the free-induction decay of \({T}_{2}^{*}=(170\pm 20)\,{{{\rm{ns}}}}\) with an exponent of n = 1.0 ± 0.2. The error bars are within the dot size. d Hahn-Echo measurement with its microwave pulse sequence in the inset. The gray solid line is a guide for the eye of a Gaussian decay curve with an amplitude of 0.9 and a decay time of 180 μs. The error bars are within the dot size.
