New color centers in diamond for long distance quantum networks

Color centers in diamond are promising candidates for quantum networks, as they can serve as solid state quantum memories with efficient optical transitions. Prior work has focused on the NV^- center in diamond, which exhibits long spin coherence times and has narrow, spin-conserving optical transitions. However, the NV^- center is prone to spectral diffusion, and over 97% of emission is in an incoherent phonon side band, severely limiting scalability. Alternatively, SiV^- exhibits excellent optical properties, with 70% of its emission in the zero phonon line and a narrow inhomogeneous linewidth. However, SiV^- suffers from short spin coherence times, limited by an orbital relaxation rate (T₁) of around 40 ns at 5 K.
Informed by the limitations of NV^- and SiV^-, we have developed new methods to control the diamond Fermi level to stabilize the neutral charge state of SiV, thus accessing a new spin configuration. SiV⁰ exhibits a spin T₁ of around 1 minute at 4 K, coherence time (T₂) approaching 1 second, over 90% of emission in the zero phonon line, and near-transform limited optical linewidths, making it a promising candidate for applications in quantum networks.
[1] B. C. Rose, D. Huang, Z. Zhang, A.M. Tyryshkin, S. Sangtawesin, S. Srinivasan, L. Loudin, M. L. Markham, A. M. Edmonds, D. J. Twitchen, S. A. Lyon, and N. P. de Leon, “Observation of an environmentally insensitive solid state spin defect in diamond,” arXiv:1706.01555 [cond-mat.mtrl-sci] (2017)
[2] B. C. Rose, G. Thiering, A.M. Tyryshkin, A. M. Edmonds, M. L. Markham, A. Gali, S. A. Lyon, and N. P. de Leon, “Strongly Anisotropic Spin Relaxation in the Neutral Silicon Vacancy Center in Diamond,” arXiv:1710.03196 [quant-ph] (2017)