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

以量子极限运行的电子和光子设备将使许多新技术成为可能，包括超快光子开关、从根本上安全的通信和量子信息处理。设计基于单量子点的单自旋光电子器件的努力面临着巨大的挑战，因为量子点的系综在能级上总是有很大的不均匀分布。能级的分布防止了基于单个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，其波长可以在比目前的单自旋比特设计大十倍的范围内进行原位调谐。此外，这些量子点分子还具有其他可调谐的光电和自旋性质，可以在单自旋量子水平上进行工程设计。该计划支持基于量子点分子的原型BIT的开发，该BIT可以分离和控制单个自旋。相干和时间分辨磁光技术将被用来开发和演示这一原型比特的操作，并量化可以实现的波长可调谐。这一结果将为生产可扩展的自旋光电子器件提供直接途径。智能价值单量子点正被积极寻求集成到光子和基于自旋的光电子器件中，但单量子点集合中的能级不均匀分布为可伸缩性提供了根本障碍。提出的基于量子点分子的新的单自旋位设计可以克服这一局限性。所提出的比特结构的关键是使用间接光学跃迁，其波长对外加电场的敏感度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只比直接跃迁弱几倍。将开发利用间接跃迁的自旋初始化、操纵和读出方法。将测量在保持自旋初始化和读出的同时可以实现的波长可调谐范围。比特设计和自旋控制协议利用最近发现的量子点分子中可调的自旋相互作用，消除了对横向磁场的需求，并纳入了非破坏性读出。这项拟议的工作将开发和展示一种自旋比特设计，其波长可调谐性至少比现有的自旋比特设计高一个数量级，从而消除了单自旋光电子器件可规模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的新课程，并为将领导下一代电子和光子设备研究的研究生提供关键培训。这项工作将进一步扩大参与暑期研究项目的本科生和教师学者的接触和机会。该项目的资金将为当地的K-12教师提供设备，将尖端的科学概念带入他们的课堂，并激励下一代学生在STEM领域追求职业生涯。

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.