Electronic structure of the neutral silicon-vacancy center in diamond

The neutrally charged silicon vacancy in diamond is a promising system for quantum technologies that combines high-efficiency optical spin initialization with long spin lifetimes (T₂≈1 ms at 4 K) and up to 90% of optical emission into its 946-nm zero-phonon line. However, the electronic structure of SiV⁰ is poorly understood, making further exploitation difficult. Performing photoluminescence spectroscopy of SiV⁰ under uniaxial stress, we find the previous excited electronic structure of a single ³A₁ᵤ state is incorrect, and identify instead a coupled ³Eᵤ-³A₂ᵤ system, the lower state of which has forbidden optical emission at zero stress and efficiently decreases the total emission of the defect. We propose a solution employing finite strain to define a spin-photon interface scheme using SiV⁰ .