First-principles study of point defect complexes in ZnO for deep-level spin qubits

Zinc oxide (ZnO) is an emerging promising material platform for hosting spin defect qubits due to its dilute nuclear spin background and potential for ultra-high purity. Shallow impurities have been previously proposed as qubit candidates, but no deep-level spin defects have been proposed. Through a first-principles computational screening of transition metal defects, we identify the molybdenum (Mo) complex vacancy defect as a promising deep-level spin qubit in ZnO. To capture the strongly correlated open-shell excited states, we employ multireference wave-function method (CASSCF) with perturbation theory and quantum defect embedding theory (QDET). We study the spin multiplet structure, spin and excited-state dynamics, and find that the combination of strong SOC and the absence of JT-distortion enable this defect as a spin qubit operating with high-fidelity single-shot readout [1]. We then expand our defect search among the s- and p- blocks of the periodic table aiming for paramagnetic deep-level defects stable within the experimental Fermi level range. We systematically evaluate single substitutions, vacancy complexes and double substitution complexes to identify candidates with stable binding energies and allowed optical transitions in the IR-visible range. We propose optimal synthesis temperatures and strategies of engineering the Fermi level position using extrinsic impurities.

[1] S. Zhang et al, “Deep Spin Defects in Zinc Oxide for High-Fidelity Single-Shot Readout”, (2025) arXiv:2502.00551