Deterministic and tunable quantum dots based on bilayer semiconductor heterostructures

量子点是能够可控地捕获单个电子的纳米级结构。这些纳米级电子器件表现出量子力学行为，这些行为可以潜在地用于实现量子计算器件，这些量子计算器件相对于当前的计算架构提供显著的计算优势。此外，这些被捕获的电子可以充当量子光源，这将有助于实现量子设备，使其免受网络攻击。在过去的20年里，光学驱动的量子点已经在各种半导体系统中得到了应用，并且已经显示出量子计算架构所需的许多必要特性。然而，先前的量子点架构还不能可靠地按比例放大到具有足够控制的大量量子点以用于量子器件。在这个项目中，一种新型的量子点将基于只有几个原子层厚的二维材料来设计。所提出的量子点由两个堆叠在一起的半导体单层组成，以实现能量可以通过电学调节的电子。使用纳米纤维技术，将在器件上形成小孔，这将形成量子点。量子点的量子特性将使用最先进的光学技术来测量。这种新的量子点架构有可能克服以前的限制，因为它提供了对量子点位置和能量的控制。这项研究符合NSF量子飞跃的大理念：通过开发有潜力实现这些新量子信息技术的材料系统来领导下一次量子革命。此外，该项目通过拟议的研究培训和指导研究生、本科生和高中生，以及鼓励亚利桑那州南部高中对STEM的兴趣，直接和间接地加强了STEM劳动力。总体项目目标是实现确定性，可扩展性和可调的量子信息设备的基础上，在新型二维（2D）材料异质结构的光驱动自旋谷电子。具体而言，纳米图案化的栅极工程架构将被探索，以实现在MoSe2-WSe2异质结构中的单电子和单激子的局域量子态。这种架构将使静电量子点（eQD）能够表现出所需的高水平的可调谐性，光谱稳定性和自旋谷量子位所需的长相干时间，并应用于量子处理和量子信息存储。在固态系统中，QD可以支持单光子发射器行为，并且一旦被充电，就可以建立长寿命的基态自旋量子位，其可以被光学相干控制，并且可能通过纠缠光子实现远程相互作用。虽然其他固态自旋系统（III-V量子点，空位中心）已经证明了单量子位的要求，但将这些固态量子位扩展到大量量子位受到量子点中的不均匀性和空位中心的光子集成挑战的限制。这些挑战激发了一种新的固态自旋量子位系统的发展，这种系统既具有确定性又具有可调性，允许控制空间位置和量子位能量。在这个项目中，新的eQD结构将被设计和制造。eQD量子态和相干特性将使用远场光谱和近场扫描光学显微镜的组合来测量。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Quantum dots are nanoscale structures capable of controllably trapping single electrons. These nanoscale electronic devices exhibit quantum mechanical behaviors which can potentially be used to realize quantum computing devices that offer significant computational advantages over current computing architectures. Furthermore, these trapped electrons can act as quantum light sources, which would help enable quantum devices that are secure against cyber-attacks. Over the past 20 years, optically driven quantum dots have been pursued in a variety of semiconductor systems and have been shown to exhibit many of the necessary properties that are required for quantum computing architectures. However, previous quantum dot architectures have not been able to reliably scale up to a large number of quantum dots with sufficient control to be used for quantum devices. In this project, a new type of quantum dot will be engineered based on two-dimensional materials which are only a few atomic layers thick. The proposed quantum dot consists of two semiconductor monolayers stacked together to realize electrons whose energies can be tuned electrically. Using nanofabrication techniques, small holes will be patterned onto the device, which will form the quantum dot. The quantum properties of the quantum dot will be measured using state-of-the-art optical techniques. This new quantum dot architecture has the potential to overcome previous limitations because it offers control over the quantum dot position and energy. This research aligns with the NSF Big Idea of the Quantum Leap: Leading the Next Quantum Revolution by developing material systems that have the potential to enable these new quantum information technologies. Furthermore, the project strengthens the STEM workforce both directly and indirectly by training and mentoring graduate, undergraduate, and high school students through the proposed research, and by encouraging interest in STEM at the high school level in southern Arizona. The overarching project objective is to achieve deterministic, scalable, and tunable quantum information devices based on optically driven spin-valley electrons in novel two-dimensional (2D) material heterostructures. Specifically, a nano-patterned gate engineering architecture will be explored to realize localized quantum states of single electrons and single excitons in MoSe2-WSe2 heterostructures. This architecture will enable electrostatic quantum dots (eQDs) that are predicted to exhibit the desired high levels of tunability, spectral stability, and long coherence times necessary for spin-valley qubits with applications in quantum processing and quantum information storage. In solid state systems, QDs can support single photon emitter behavior and, once charged, establish a long-lived, ground-state spin qubit that can be coherently controlled optically and potentially realize long range interactions via entangled photons. Although other solid-state spin systems (III-V QDs, vacancy centers) have demonstrated the single qubit requirements, scaling these solid-state qubits to large numbers has been limited by inhomogeneity in QDs and photonic integration challenges for vacancy centers. These challenges motivate the development of a new solid-state spin qubit system that is both deterministic and tunable—allowing for control of both the spatial placement and qubit energy. In this project, novel eQD structures will be engineered and fabricated. The eQD quantum states and coherence properties will be measured using a combination of far-field spectroscopy and near field scanning optical microscopy. Coherent control of single spin-valley qubits will be demonstrated using coherent nonlinear spectroscopy.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.