Telecom-wavelength NV-center analogs in cubic boron nitride

We apply first-principles calculations to investigate V-B-C-B and V-B-Si-B complexes in cubic boron nitride as potential quantum defects. We find that these centers possess a triplet ground-state spin, analogous to that of the prototype quantum defect, the NV center in diamond. In contrast, the main optical transition of these complexes occurs in the telecom O-band, making them appealing for quantum networking applications. Furthermore, the coupling to phonons is weaker than in the NV center, resulting in a much larger fraction of photons (22%) being emitted in the zero-phonon line. One inherent drawback of the longer emission wavelength is stronger nonradiative recombination; however, the resulting lower quantum efficiency can be mitigated by cavity coupling.