Properties of shallow donor ensembles in ZnO for quantum memory applications*

Neutral shallow donors (D⁰) in ZnO, such as Al_Zn, Ga_Zn, In_Zn, are promising solid-state spin qubits¹. D⁰ optically couples to the neutral donor bound exciton (D⁰X) with high radiative efficiency, potentially enabling photon-mediated quantum entanglement schemes both between donors, and donors and trapped-ions². Here we report on the optical ensemble properties of ZnO donors, toward quantum memory applications (QMA). The optical D⁰X transition exhibits an inhomogeneous linewidth of 20 GHz measured via photoluminescence excitation, and optical absorption. The 0-field optical depth (OD) for the Al and Ga transitions is 10 and 6, respectively, and dramatically decreases at field due to optical pumping. We will further present spectral hole burning measurements to determine the upper bound homogeneous linewidth and discuss the diffrent line broadening contributions. The large OD, homogeneous optical properties and potential to extend spin-coherence times indicate ZnO donor ensembles are promising for QMA.
[1] Linpeng et al. Phys. Rev. Appl. 10 (2018)
[2] Lilieholm et al. Appl. Phys. Lett. 117 (2020)