Transition Metal Complex in Zinc Oxide as Deep-Level Spin Defect Qubits

Zinc Oxide (ZnO) is a promising candidate for hosting point defects as spin qubits for quantum information science and technology (QIST),due to its wide band gap, unique electronic properties, and inherently low spin-noise environment. Previously, shallow impurities in ZnO were mostly proposed as spin qubit candidates, but deep spin defect studies in ZnO are rather sparse, which ideally decouple with the host materials for stable operation.In this work, our theoretical research focuses on identifying deep point defects in ZnO with optimal critical physical properties for QIST. Using the first-principles calculations, we predict molybdenum (Mo) vacancy defect in ZnO as the most promising candidate due to its thermodynamic stability, optical visibility and spin properties. We investigated the optical properties of the allowed defect-defect transitions extensively, including absorption and photoluminescence spectroscopy, the zero phonon line (ZPL) and radiative/non-radiative recombination process affecting quantum yield.

Notably, we found drastically different non-radiative recombination rates between candidates, leading to significant differences in their quantum yields.

We demonstrated the strong spin-orbit coupling between triplet and singlet states of the defect, which contributes to intersystem crossing during the spin-qubit initialization process. Additionally, we simulated the spin-decoherence time(T2) of the proposed candidates, and observed interesting behavior related to nuclei quadrupole interaction and electron impurities.

Our research provide comprehensive insight that are crucial for understanding and controlling defect behaviors in ZnO, paving the way for the precise development of quantum technologies.