Recent samples from E6 appear to have favorable properties both in terms of NV concentrations and coherence properties. We are working with E6, NVision and Fraunhofer to further optimize samples including nano-structuring and focusing on very shallow NVs.
 We have developed and demonstrated robust pulse sequences that are relevant for the control of large ensembles of spins, for which inhomogeneous broadening is significant (together with F. Jelezko and A. Retzker, see Phys. Rev. Research 2, 033216, 2020).
 We have also studied coherence and entanglement effects within the spin bath in polarization transfer schemes, realizing the possibility of formation of dark states, as well as suggesting a modified scheme to overcome them (together with G. Kurizki, New Journal of Physics 22, 083035, 2020).
 Finally, we have developed a new framework for the control of interacting spin ensembles, which extends the familiar Clifford pulse basis to a higher symmetry group, thus enabling complete control over the quantum many-body dynamics of the system (Phys. Rev. Research 2, 013061, 2020).