Engineering deterministic electron correlations and topological states in site-controlled III-V quantum droplets

非技术描述：今天的计算机是用半导体硅制造的晶体管制造的。这类晶体管的改进正在放缓，并将在未来几年内走到尽头。量子计算是一种新的计算方式，它打破了当前的计算方式。这种方法，使用量子力学元素称为量子位，需要新的材料和方法。这些量子比特及其相互作用非常脆弱，因此在创建量子计算机时，防止量子错误至关重要。该项目将利用一种被称为拓扑保护的效应来研究非常健壮的量子力学元素（量子门）的形成。拓扑保护意味着在p波超导体中使用复合费米子涡旋，这些涡旋服从非阿贝尔量子统计量，被称为非阿贝尔任意子。拓扑量子门的物理实现意味着使用固态平台提供一组局部非阿贝尔任意子，结合“镊子”来执行编织和融合，以及相位检测器。该项目涉及圣母大学、爱尔兰共和国廷德尔国家研究所和北爱尔兰贝尔法斯特女王大学的小组合作，开发和研究一种基于in (Ga)P/GaInP量子霍尔水坑的拓扑量子门的新材料系统。目标是产生确定性量子霍尔水坑，包含一组局部非阿贝尔任意子，可用于大规模量子计算。该项目还通过为材料加工和表征、纳米制造和实验测量领域的本科生和研究生提供研究和培训经验，帮助开发人力资源。技术描述：防止量子错误是实现量子计算的关键。科学界的一项研究是基于这样一种期望，即在基于拓扑状态构建的量子比特的量子计算系统中，将出现对量子操作的强保护。一个实现这种容错拓扑量子计算的有效平台可以使用支持所谓的马约拉纳零模式（MZMs）的强相关电子系统，具有非阿贝尔量子统计量。这种拓扑量子态是在量子霍尔效应中首次发现的，它们由涡旋复合费米子准粒子表示，称为任意子，由附着在一维和二维p波超导体中的电子/空穴或缺陷上的磁通量量子组成。已知几种支持mzm的复合费米子系统，但在量子处理器中实现它们的途径尚未很好地定义，主要是因为难以实现基于这些准粒子的量子位元控制。这个国际合作项目旨在开发和研究一种实现MZMs的新系统：量子霍尔水坑。利用近场扫描光学显微镜对量子霍尔水坑进行了初步实验，观察到复合费米子。这开启了创建本地化mzm的可能性，具有许多重要的优势，例如相对较高的工作温度，零外部磁场，以及执行编织和融合的静电“镊子”。目标是生产确定的量子霍尔水坑，以支持在in (Ga)P/GaInP系统中使用选择性区域外延的本地化MZMs的“大规模”开发，并开发扫描电荷探针技术用于其表征。这些量子霍尔水坑的产生是量子计算机可扩展方法发展的重要一步。利用结构表征、光谱学和纳米电子电荷测量对生长的结构进行了研究，并用于制备候选量子门。该奖项反映了美国国家科学基金会的法定使命，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。

Nontechnical description: Todays computers are built using transistors fabricated in the semiconductor silicon. Improvements in these kinds of transistors are slowing, and will come to an end in the next few years. Quantum computing is a new way of doing computation that breaks with the way computing is currently done. This approach, using quantum mechanical elements called qubits, requires new materials and approaches. These qubits and their interactions are very fragile, so protection from quantum errors is critical in creating a quantum computer. This project will investigate the formation of very robust quantum mechanical elements (quantum gates) using an effect known as topological protection. Topological protection implies using composite fermions vortexes in a p-wave superconductor which obey non-Abelian quantum statistics and are known as non-Abelian anyons. A physical realization of topological quantum gate implies the use of solid-state platforms providing a set of localized non-Abelian anyons combined with a "tweezer" to perform their braiding and fusion, and a phase detector. The project involves a collaboration of groups at the University of Notre Dame, the Tyndall National Institute in the Republic of Ireland, and Queen's University Belfast in Northern Ireland, to develop and investigate a new material system for a topological quantum gate, based on In(Ga)P/GaInP quantum Hall puddles. The goal is to produce deterministic quantum Hall puddles, containing a set of localized non-Abelian anyons, that can be used in large scale quantum computing. This project also helps in the development of human resources by providing research and training experience to undergraduate and graduate students in the areas of materials processing and characterization, nanofabrication and experimental measurements.Technical description: Protection from quantum errors is a critical point in the realization of quantum computing. One line of research in the scientific community is based on the expectation that strong protection for quantum operations will occur in quantum computation systems based on qubits built from topological states. An efficient platform for the realization of such fault tolerant topological quantum computing could be built using strongly correlated electron systems supporting the so-called Majorana zero modes (MZMs), having non-Abelian quantum statistics. Such topological quantum states were first detected in the quantum Hall effect, and they are represented by vortex composite fermion quasiparticles, known as anyons, composed of magnetic flux quanta attached to electrons/holes or defects in one and two-dimensional p-wave superconductors. Several composite fermion systems are known which supports MZMs, but routes to their implementation in a quantum processor are not well defined, primarily due to difficulties in implementing the control of qubits based on these quasiparticles. This international collaborative project aims to develop and investigate a novel system to realize MZMs: a quantum Hall puddles. Composite fermions were observed in preliminary experiments with quantum Hall puddles using near-field scanning optical microscopy. This opens the possibility for creating localized MZMs, with a number of non-trivial advantages, such as a relatively high operating temperature, zero external magnetic fields, and electrostatic "tweezers" to perform braiding and fusion. The goal is to produce deterministic quantum Hall puddles to support "large scale" development of localized MZMs using selective area epitaxy in the In(Ga)P/GaInP systems and development of scanning charge probe techniques for their characterization. Production of these quantum Hall puddles is an important step in the development of a scalable approach to quantum computers. The grown structures are studied by using structural characterization, optical spectroscopy, and nanoelectronic charge measurements, and used to fabricate candidate quantum gates.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.