CAREER: Tunable superconductor materials for quantum information processing using pairs of Majorana zero modes

非技术摘要：量子计算利用量子力学过程进行信息存储和操作，预计将超越经典计算方案。最近，量子计算机的原型已经证明了在传统计算机难以或不可能执行的任务上的计算能力。然而，要实现一个可以执行通用计算任务的全尺寸量子计算机，首先需要解决量子退相干的关键问题-这是一个导致量子信息丢失和错误产生的过程。解决这一挑战的一个有希望的方法是利用一种奇异的量子粒子，称为马约拉纳费米子，与它们的反粒子无法区分。这种独特的性质允许人们使用一对耦合的马约拉纳费米子来构建量子计算的基本元素，即量子比特或量子比特，这可以产生一种新型的量子比特，这种量子比特自然地受到保护而不受退相干的影响。该项目旨在整合所需的元素，使用新的超导材料构建这种量子位的原型。该项目的重点是对研究生和本科生、K-12学生和教师的教育和推广计划，并与研究工作相结合，以建立下一代量子知识的劳动力。技术摘要：该项目为构建拓扑量子比特奠定了材料和设备基础-这种量子比特可以防止退相干。这项研究利用了被称为拓扑超导体的新材料，这种材料在内部具有超导能隙，在边界处具有马约拉纳零模式。候选材料是二维（2D）系统和异质结构，其中超导性，磁性和自旋轨道耦合共存，例如（111）取向的金耦合到超导体和磁性绝缘体的表面状态。这种材料具有高度的可调谐性，并允许通过操纵超导体材料本身的性质来控制马约拉纳零模式。同时，聚焦材料是可扩展的，这使得它们可以通过遵循标准制造程序容易地制造成所需的纳米结构/器件。研究遵循量子信息处理的“基于测量”方案，该方案利用量子态隐形传态的概念，通过一对马约拉纳零模。该项目旨在实现拓扑量子位的几个里程碑，其中包括：1。证明了一对耦合的Majorana零模的量子非定域性; 2.使用可调谐超导体材料控制马约拉纳零模式;以及3.演示拓扑量子比特的干涉仪设备。该项目的成功为理解异质结构材料中出现的新量子相提供了一条途径，并将刺激量子信息科学。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。

Non-technical abstract:Quantum computing, which leverages quantum mechanical processes for information storage and manipulation, is expected to surpass classical computing schemes. Recently, prototypes of quantum computers have demonstrated computing power on tasks that are difficult or impossible to be carried out by a conventional computer. However, to achieve a full-scale quantum computer which can carry out universal computation tasks, the critical issue of quantum decoherence – a process that causes the loss of quantum information and the generation of errors, needs to be addressed first. One promising way to tackle this challenge is to utilize a kind of exotic quantum particles, known as Majorana fermions, that are indistinguishable from their antiparticles. Such unique property allows one to construct the basic element of quantum computing, i.e. a quantum bit or qubit, using a pair of coupled Majorana fermions, which can give rise to a new type of qubit that is naturally protected from decoherence. This project aims to integrate the needed elements to build prototypes of such qubit using new superconductor materials. The project emphasizes on the education and outreach program for graduate and undergraduate students, and K-12 students and schoolteachers, which are combined with the research endeavors to build a next generation quantum-literate workforce.Technical abstract:The project establishes the material and device foundation for building a topological qubit – the kind of qubit that is protected against decoherence. The research exploits new materials known as topological superconductors, which have superconducting energy gap in their interiors and harbor Majorana zero modes at their boundaries. The candidate materials are two-dimensional (2D) systems and heterostructures, in which superconductivity, magnetism and spin-orbit coupling co-exist, such as the surface state of (111)-oriented gold coupled to a superconductor and a magnetic insulator. Such materials feature a high degree of tunability and allow the control of Majorana zero modes by manipulating the properties of the superconductor materials themselves. At the same time, the focused materials are scalable, which allows them to be easily fabricated into the needed nano structures/devices by following standard fabrication procedures. The research follows the “measurement-based” scheme for quantum information processing, which utilizes the concept of quantum state teleportation through a pair of Majorana zero modes. The project aims to achieve several milestones towards achieving a topological qubit, which includes: 1. prove the quantum non-locality of a pair of coupled Majorana zero modes; 2. control Majorana zero modes using tunable superconductor materials; and 3. demonstrate interferometer devices for topological qubit. The success of the project offers a path towards understanding the novel quantum phases emerging in material heterostructures and will stimulate quantum information sciences. The outcome will advance both basic science and information technology, paving the way for the next generation computation.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.