Coherence properties of shallow donor qubits in ZnO

• Published in: arXiv.org 2018-05
• Main Authors: Linpeng, Xiayu, Viitaniemi, Maria L K, Vishnuradhan, Aswin, Kozuka, Y, Johnson, Cameron, Kawasaki, M, Fu, Kai-Mei C
• Format: Article
• Language: English
• Subjects: Crystal defects; Diffusion; Electron spin; Hyperfine structure; Inhomogeneity; Nuclear spin; Optical control; Optical properties; Organic chemistry; Quantum theory; Qubits (quantum computing); Relaxation time; Zinc oxide
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1802.03483

Defects in crystals are leading candidates for photon-based quantum technologies, but progress in developing practical devices critically depends on improving defect optical and spin properties. Motivated by this need, we study a new defect qubit candidate, the shallow donor in ZnO. We demonstrate all-optical control of the electron spin state of the donor qubits and measure the spin coherence properties. We find a longitudinal relaxation time T\(_1\) exceeding 100 ms, an inhomogeneous dephasing time T\(_2^*\) of \(17\pm2\) ns, and a Hahn spin-echo time T\(_2\) of \(50\pm13\) \(\mu\)s. The magnitude of T\(_2^*\) is consistent with the inhomogeneity of the nuclear hyperfine field in natural ZnO. Possible mechanisms limiting T\(_2\) include instantaneous diffusion and nuclear spin diffusion (spectral diffusion). These results are comparable to the phosphorous donor system in natural silicon, suggesting that with isotope and chemical purification long qubit coherence times can be obtained for donor spins in a direct band gap semiconductor. This work motivates further research on high-purity material growth, quantum device fabrication, and high-fidelity control of the donor:ZnO system for quantum technologies.