Semiconductor electron-nuclear spin qubits with optical access

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NON-TECHNICAL DESCRIPTIONQuantum information systems have capabilities not possible in the classical domain. These systems rely on different types of quantum bits, or qubits, to perform different tasks. For example, photons may be used for quantum communications, electrons for quantum calculations and nuclear spins for quantum memories. Generally, it is challenging to transfer information between different types of qubits. This research project will investigate an emerging quantum material, indium-doped zinc oxide, with the potential to serve as the basis for a combined photonic, electronic and nuclear qubit system. Single qubit isolation with access to a nuclear spin memory in a semiconductor platform could lead to scalable quantum networks. Such networks can be utilized for quantum communication, a form of fundamentally secure communication, and quantum computation. In addition, we expect further understanding of the fundamental properties of donors to impact a large set of semiconductor technologies. The project will provide research training in experimental quantum information to undergraduate and students. Quantum workforce training is currently in high demand due to the large industry and government investment in quantum technologies. TECHNICAL DESCRIPTIONDefects in crystals are one of the most advanced qubit platforms for quantum network applications. They may boast 3 types of physical qubits in a single system: nuclear spins, electron spins and photons suitable for quantum memory, processing and communication, respectively. This research focuses on a particular promising quantum point defect, the shallow indium donor in the zinc oxide (ZnO) semiconductor host. The In:ZnO system has the long-term potential to combine an efficient optical interface and electronic control in a system that can be deterministically created. Toward this end, the goal of this project is(1) to realize high yield doping with single donor isolation in high-purity ZnO and (2) control over the electron-nuclear spin interface to enable a quantum memory with potential for second-long storage. Highly homogeneous optical transitions, longitudinal spin-relaxation times approaching 1s, 50 microsecond quantum memory times, electron spin qubit initialization and coherent population trapping have all been realized in the donor:ZnO system. Two primary challenges remain to leverage this semiconductor system for quantum technologies: single donor isolation and nuclear spin control. The challenge in single donor isolation is the high donor density in ZnO substrates. Here, we employ a strategy based on ultra-high purity ZnO grown by molecular beam epitaxy, photonics fabrication designed to selectively probe this layer, and implantation of single/few donors. Toward nuclear spin control, the team will develop techniques to realize optical nuclear spin pumping, optically detected electron spin resonance and nuclear spin resonance to access the indium nuclear spin-9/2 quantum memory. The PI has a track record in broadening the participation of women in STEM and quantum information that will continue under this award. Finally, the activity will include support for the UW Science Explorers, which brings together graduate student volunteers, an elementary-school teacher, and elementary school students to conduct science and engineering experiments and activities at an economically and racially diverse Title 1 Seattle public school.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.