Spin-Photon Interface and Optical Readout of Spin Defects from First-Principles Calculations

For initialization and readout of spin states, an optical interface is generally desired for its practical ease of use and isolating spin qubits. An efficient spin-photon interface requires knowledge of key optical parameters, including photoluminescence (PL) spectra, quantum efficiency, and spin-dependent optical contrast (PL contrast) through optically detected magnetic resonance (ODMR). In particular, high quantum efficiency and large PL contrast ensure reliable spin information readout. First-principles tools of predicting readout efficiency for spin qubits are highly desirable as such predictions can be directly compared to experiments and used as target parameters for qubit optimization. However, prediction of PL contrast requires knowledge of all kinetic processes, which need to include interactions among spin, photon, phonon, electron and exciton for spin defects. In this talk, we show our recent development on spin-dependent PL contrast and ODMR including all radiative, nonradiative and intersystem crossing rates, with defect-exciton, electron-phonon couplings and spin-orbit interactions, entirely from first-principles calculations [1]. We show that our method provides excellent agreement with experimental PL contrast and ODMR spectra for NV center in diamond. We then apply it to predict spin-related optical properties in carbon defects in hexagonal Boron-Nitride, an emerging material platform for hosting spin qubits. Our work provides the computational platform for optimizing spin-photon interface and predicting optical readout efficiency of spin qubits from first-principles. [1] T. Smart et al, npj Comput. Mater. 7, 59, (2021).