Mechanism for selective initialization of silicon-vacancy spin qubits with S = 3/2 in silicon carbide

Abstract

The silicon vacancy in silicon carbide has emerged as a promising quantum system embedded in an industry-friendly platform due to its long-lived spin qubits that can effectively interface with photonic qubits. However, the unique spin quantum number of 3/2 gives rise to a statistical mixture of the optically initialized ground-state spin sublevels, hindering its successful application as a high-fidelity spin-photon interface. Recent experimental breakthroughs have demonstrated a solution to this challenge by achieving pure-state preparation through simultaneous optical initialization and depletion of selected spin sublevels using electron spin resonance. Nonetheless, the underlying mechanism of this process remains poorly understood, and an efficient method for achieving deterministic initialization has not yet been explored. In this work, we present a comprehensive investigation of the selective initialization process by establishing a complete rate model. We offer a detailed explanation of the underlying mechanism and elucidate the trade-off between initialization fidelities and efficiencies, which are strongly influenced by the experimental parameters employed. Through a thorough exploration of a wide range of experimental parameters, we identify the optimal initialization process that allows for pure-state initialization fidelity exceeding 99%. Our study offers valuable insights into achieving high-fidelity spin-photon interface applications, such as quantum repeaters, based on silicon vacancies in silicon carbide. © 2024 American Physical Society.