Figure 1

(a) Simplified level scheme of NV center with relevant $\Lambda$ system (cf. the text and 10). (b) Sketch of relevant processes: electronic ground states are coupled by optical pumping and HF flipflops; the states are labeled by the $z$ components of the electron and nuclear spin. (c) $I_{\mathrm{coop}}/I_{\mathrm{ind}}$ for randomly chosen nuclear environments of an NV center. The first nuclear shell is taken to be spinless, as due to their very strong coupling they would evolve largely independent from the ensemble.Reuse & Permissions

Figure 2

Relative intensity under dynamical Overhauser field compensation: $N={21}^2$, ${\omega }_S=A/2$, and $ϵ=0.3$(I), 0.7(II), 0.99(III). (IV) shows the ideal Dicke SR profile [1] as a reference. Inset: comparison of exact evolution and factorization for $N=9$ inhomogeneously coupled spins (left peak, scaled by factor 50) and $N={21}^2$ homogeneous spins ($ϵ=0.7$). Fully independent emitters lead to an exponential curve slowly decaying from 1 to zero and are therefore not depicted.Reuse & Permissions

Figure 3

$I_{\mathrm{coop}}/I_{\mathrm{ind}}$ for different values of $ϵ$—the Overhauser field is dynamically compensated and ${\omega }_S=A/2$ in all cases—compared to the ideal Dicke case. The dashed line corresponds to a partially polarized dot (cf. the text).Reuse & Permissions