Donor Electron Spins in Direct Bandgap Semiconductors for Quantum Networks

量子信息网络有望在优化问题的计算、加密破解和材料模拟方面取得突破，并实现从根本上安全的通信。晶体中的量子缺陷已经显示出实现可扩展量子网络所需的一些特征；然而，寻找一个同时表现出所有必要的光学和量子属性的系统仍然具有挑战性。基于有希望的初步结果，氧化锌中的单施主缺陷可能满足这些标准。该项目将演示单个氧化锌施主的创建和检测，以及对施主电子和原子核的完全控制和表征。目标是确定该系统在可扩展量子信息应用方面的前景。此外，对氧化锌中单施主杂质的研究可能会导致研究半导体中掺杂的新技术，并将培养一批不同的量子光学和纳米技术研究生和本科生，为他们在国家实验室、工业和学术界的职业生涯做好准备。基于缺陷的量子信息处理由于潜在的器件集成、自旋光子转移的可能性以及高纯度晶体中长的量子相干时间而具有吸引力。对于有光辐射的缺陷系统，基于测量的协议可以用来在非相互作用的、远程分离的量子比特之间创建量子网络。本项目将研究一种具有良好光学性质的缺陷系统，即氧化锌中的施主系统，它在零声子线上具有均匀的光学跃迁和接近单位的辐射效率。先前对供体的研究表明，如果有同位素纯化的氧化锌晶体可用，供体系统的相干时间可能会很长。在这里，将使用不同的技术来隔离单个施主：单个小直径的氧化锌纳米线的生长，以及纳米级掩蔽或聚焦离子束刻蚀结合低施主密度的外延氧化锌层。单个供体的隔离将通过光子自相关测量来确认。用于高保真相干控制的光抽运和微波脉冲将被用来研究单个氧化锌施主的光学和自旋(电子和核)相干特性，测试该系统作为量子比特候选者的适用性。由于施主的有效质量性质，有可能将在氧化锌中发现的量子性质推广到直接带隙半导体中的整个施主类别，从而进一步促进这项研究的影响。该项目由数学和物理科学局物理部的量子信息科学(QIS)计划和数学和物理科学局材料科学部的凝聚态物理(CMP)计划和电学部的电子、光子和磁器件(EPMD)计划共同资助。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Quantum information networks are expected to enable breakthroughs in computation for optimization problems, encryption-breaking, and materials simulation, as well as realize fundamentally secure communication. Quantum defects in crystals have been shown to exhibit some of the characteristics needed to realize a scalable quantum network; however finding a system that simultaneously exhibits all of the requisite optical and quantum properties remains challenging. Based on promising preliminary results, single donor defects in zinc oxide (ZnO) may satisfy these criteria. This project is to demonstrate single ZnO donor creation and detection with complete control and characterization of the donor electron and nucleus. The goal is to determine the outlook of this system for scalable quantum information applications. In addition, the study of single donor impurities in ZnO may lead to new techniques for studying dopants in semiconductors and will train a diverse group of graduate and undergraduate students in quantum optics and nanotechnology, preparing them for careers in national laboratories, industry, and academia.Defect-based quantum information processing is attractive due to the potential for device integration, the possibility of spin-photon transfer, and the long quantum coherence time in high-purity crystals. For defect systems with optical radiation, measurement-based protocols can be utilized to create quantum networks between non-interacting, remotely separated qubits. This project will investigate a defect system with favorable optical properties, i.e. the donor system in ZnO, which has homogeneous optical transitions and near-unity radiative efficiency in the zero phonon line. Prior studies in an ensemble of donors showed the potential for long coherence times of the donor system if isotopically purified ZnO crystal is available. Here, different techniques will be utilized to isolate single donors: growth of single ZnO nanowires with small diameters, and nano-scale masking or focused ion beam etching combined with epitaxial ZnO layers of low donor density. The isolation of single donors will be confirmed by a photon autocorrelation measurement. Optical pumping and microwave pulses for high-fidelity coherent control will be used to study the optical and spin (electron and nuclear) coherence properties of single ZnO donors, testing the suitability of this system as a qubit candidate. Due to the effective mass nature of the donor, it may be possible to generalize the quantum properties found in ZnO to the entire class of donors in direct band gap semiconductors, furthering the impact of this research.This project is jointly funded by the Quantum Information Science (QIS) Program in the Physics Division in the Directorate for Mathematical and Physical Sciences, and the Condensed Matter Physics (CMP) Program in the Division of Materials Science in the Directorate for Mathematical and Physical Sciences, and the Electronics, Photonics and Magnetic Devices (EPMD) Program in the Division of Electrical, Communications and Cyber Systems Division in the Engineering Directorate.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.