Formation of Shallow Indium Donor Qubits in ZnO via Ion Implantation

The indium substitutional donor (In⁰_Zn) in ZnO is an emerging semiconductor spin qubit with optical access via the donor-bound exciton (In⁰_ZnX). In this work, we controllably introduce In⁰_Zn into ZnO as a donor via ion implantation and post-implantation annealing. The inhomogeneous optical linewidths for the implanted In⁰_ZnX transition is 7 GHz at 2 K, comparable to what is observed for in-grown In⁰_Zn ensembles in commercially-available ZnO single crystals, and only 20 times broader than the lifetime-limited linewidth. The longitudinal spin relaxation time (T₁) of implanted In⁰_Zn is measured to be 4 ms at 7 T, four times longer than what has been found for in-grown Ga donors in our previous work [1]. T₁ increases with decreasing magnetic field following the expected inverse power-law [2]. Optical pumping and coherent control of the implanted In⁰_Zn is shown using two resonant lasers at 7 T. All-optical coherent control is demonstrated via coherent population trapping (CPT). The CPT signature observed at low excitation powers indicates the presence of ten distinct features, as expected due to the strong hyperfine interaction between the electron bound to In⁰_Zn and the In nuclei (spin = 9/2). Our results indicate that for implanted In⁰_Zn access of nuclear spin degrees of freedom for quantum memories may be achievable.

[1] Xiayu Linpeng, et. al., Phys. Rev. Appl. 10, 064061 (2018).

[2] Vasileios Niaouris, et. al., Phys. Rev. B 105, 195202 (2022).