Hidden Silicon-Vacancy Centers In Diamond

We characterize a high-density sample of negatively charged silicon-vacancy (SiV-) centers in diamond using collinear optical multidimensional coherent spectroscopy. By comparing the results of complementary signal detection schemes, we identify a hidden population of SiV- centers that is not typically observed in photoluminescence and which exhibits significant spectral inhomogeneity and extended electronic T-2 times. The phenomenon is likely caused by strain, indicating a potential mechanism for controlling electric coherence in color-center-based quantum devices.