Deterministic and tunable quantum dots based on bilayer semiconductor heterostructures

量子点是一种纳米级结构，能够可控地捕获单电子。这些纳米尺度的电子设备表现出量子力学行为，这些行为可能被用来实现量子计算设备，与当前的计算体系结构相比，量子计算设备具有显著的计算优势。此外，这些被捕获的电子可以作为量子光源，这将有助于使量子设备能够安全地免受网络攻击。在过去的20年里，光驱动量子点在各种半导体系统中得到了追求，并被证明具有量子计算体系结构所需的许多必要性质。然而，以前的量子点体系结构无法可靠地放大到具有足够控制的大量量子点，以用于量子设备。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半导体单分子层堆叠在一起，实现了能量可以电子调谐的电子。利用纳米制造技术，将在设备上形成小孔，从而形成量子点。量子点的量子性质将使用最先进的光学技术进行测量。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。这项研究与NSF关于量子飞跃的大想法是一致的：通过开发有可能实现这些新的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对研究生、本科生和高中生进行培训和指导，并通过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的劳动力。该项目的总体目标是在新型二维材料异质结构中实现基于光驱动的自旋谷电子的确定性、可伸缩和可调谐的量子信息设备。具体地说，将探索一种纳米图案化的栅工程结构，以实现MoSe2-WSe2异质结中单电子和单激子的局域量子态。这种体系结构将使静电量子点(EQD)能够表现出所需的高水平的可调性、光谱稳定性和长相干时间，这是自旋谷量子比特在量子处理和量子信息存储中应用所必需的。在固态系统中，量子点可以支持单光子发射体行为，一旦充电，就可以建立一个长寿命的基态自旋量子比特，可以通过光学相干控制，并有可能通过纠缠光子实现长程相互作用。尽管其他固态自旋系统(III-V量子点，空位中心)已经证明了单量子比特的要求，但由于量子点的不均匀性和空位中心的光子集成挑战，这些固态量子比特的大规模扩展受到了限制。这些挑战推动了一种新的固态自旋量子比特系统的发展，这种系统既是确定性的，也是可调的--允许控制空间位置和量子比特能量。在这个项目中，将设计和制造新型的EQD结构。将使用远场光谱和近场扫描光学显微镜的组合来测量EQD的量子态和相干性。单自旋谷量子比特的相干控制将使用相干非线性光谱学进行演示。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 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.