Developing a tunable single-spin bit for scalable spin-based optoelectronics

在量子极限下运行的电子和光子器件将使许多新技术成为可能，包括超快光子开关、基本安全通信和量子信息处理。基于单量子点的单自旋光电器件的设计面临着巨大的挑战，因为量子点的集成在能级上总是具有很大的不均匀分布。能级的分布阻止了基于单量子点的自旋比特被集成到多比特设备中，在多比特设备中，每个比特必须与离散数量的固定激光或光学腔波长调谐成共振。最近的发现表明，量子点分子具有光学跃迁，其波长可以在原位调谐，其范围是目前单自旋比特设计的10倍。此外，这些量子点分子具有其他可调谐的光电和自旋特性，可以在单自旋量子水平上进行设计。该程序支持基于量子点分子的原型比特的开发，可以隔离和控制单个自旋。相干和时间分辨磁光技术将用于开发和演示该原型钻头的操作，并量化可以实现的波长可调性。该结果将为生产可扩展的基于自旋的光电器件提供直接途径。单量子点正被积极地用于光子和基于自旋的光电器件的集成，但是单量子点集成中能级的不均匀分布为可扩展性提供了一个基本障碍。基于量子点分子的单自旋比特设计可以克服这一限制。所提出的位结构的关键要素是使用间接光学跃迁，其波长对外加电场的敏感性比单个量子点的跃迁高一个数量级。实验表明，这些间接跃迁的偶极矩阵元素仅比直接跃迁弱几倍。将开发利用间接过渡的自旋初始化、操作和读出方法。在保持自旋初始化和读数的同时，波长可调谐范围将被测量。位设计和自旋控制协议利用了最近在量子点分子中发现的可调谐自旋相互作用，从而消除了对横向磁场的需求，并结合了无损读出。所提出的工作将开发和演示一种自旋比特设计，其波长可调性至少比现有的自旋比特设计高一个数量级，从而消除单自旋光电器件可扩展生产的最大障碍之一。更广泛的影响拟议中的工作将丰富已经在开发中的新课程，并为领导下一代电子和光子器件研究的研究生提供重要的培训。这项工作将进一步扩大本科生和教师学者参与暑期研究项目的机会。该项目的资金将为当地K-12教师提供设备，将尖端科学概念带入课堂，并激励下一代学生在STEM领域从事职业。

Electronic and photonic devices that operate at the quantum limit will enable many new technologies, including ultrafast photonic switches, fundamentally secure communication, and quantum information processing. Efforts to engineer single-spin optoelectronic devices based on single quantum dots have faced significant challenges because ensembles of quantum dots always have a large inhomogeneous distribution in energy levels. The distribution in energy levels prevents spin bits based on single quantum dots from being integrated into multi-bit devices where each bit must be tuned into resonance with a discrete number of fixed laser or optical cavity wavelengths. Recent discoveries have demonstrated that quantum dot molecules have optical transitions whose wavelength can be tuned in situ over a range ten times larger than available in present single-spin bit designs. Moreover, these quantum dot molecules have other tunable optoelectronic and spin properties that can be engineered at the single-spin quantum level. This program supports development of a prototype bit, based on quantum dot molecules, that can isolate and control a single spin. Coherent and time-resolved magneto-optical techniques will be used to develop and demonstrate operation of this prototype bit and quantify the wavelength tunability that can be achieved. The results will provide a direct path to the production of scalable spin-based optoelectronic devices. Intellectual MeritSingle quantum dots are being actively pursued for integration into photonic and spin-based optoelectronic devices, but the inhomogeneous distribution of energy levels in ensembles of single quantum dots provides a fundamental barrier to scalability. This limitation can be overcome with the proposed new single-spin bit design based on quantum dot molecules. The key element of the proposed bit architecture is the use of indirect optical transitions whose wavelength is an order of magnitude more sensitive to applied electric field than the transitions of single quantum dots. Experiments have shown that these indirect transitions can have dipole matrix elements only a few times weaker than direct transitions. Spin initialization, manipulation and readout methods that utilize the indirect transitions will be developed. The range of wavelength tunability that can be achieved while maintaining spin initialization and readout will be measured. The bit design and spin-control protocols take advantage of recently discovered tunable spin interactions in quantum dot molecules to eliminate the need for transverse magnetic fields and incorporate nondestructive readout. The proposed work will develop and demonstrate a spin-bit design with at least an order of magnitude more wavelength tunability than existing spin-bit designs and consequently eliminate one of the largest obstacles to the scalable production of single-spin-based optoelectronic devices. Broader ImpactsThe proposed work will enrich new courses already under development and provide crucial training for graduate students who will lead the next generation of electronic and photonic device research. The work will further broaden the exposure and opportunities for undergraduates and teacher-scholars participating in summer research programs. Funds from this program will provide local K-12 teachers with equipment to bring cutting-edge scientific concepts into their classrooms and inspire the next generation of students to pursue careers in STEM fields.