The initialization fidelity of the nuclear spins into |↓↓↓> as a function of the number of repetitions ( N ) of the initialization protocol for different initial nuclear spin states. Error bars correspond to ±1 s.d. about the mean. The fidelity increases for more iterations, indicating robustness. That is, the initialization protocol can be applied multiple times to increase the fidelity to achieve F=100-6+0 %.
