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 one promising candidate due to its thermodynamic stability, optical accessibility and spin properties. We applied the a combination of advanced electronic structure methods and kinetic theory to describe the optical excitations and dynamics and 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 viability of spin-orbit assisted 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 impurity spins.
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.

Acknowledge AFOSR CFIRE project under grant number
FA9550-23-1-0418