Nonequilitrium effects in nanostructures: applications to solid state quantum computation and spintronics

传统半导体技术的长期进步预计将在未来10到20年内停滞。随着晶体管尺寸接近纳米级，与小型化和能量耗散相关的严重问题将阻碍传统器件的进一步改进。这一预期正在推动替代设备的开发，这些设备在原子尺度上利用量子性质。一个值得注意的例子是量子计算机的概念，其中每个比特由一个原子或一组几个原子组成，量子力学的规则决定了信息处理的方式。另一种有趣的替代方法是自旋电子学，其中电子的自旋而不是电荷形成了经典存储器和逻辑的基础，承诺每个设备的能量耗散率要低得多。这项研究项目解决了与基于半导体、超导和磁性纳米结构的量子计算机和自旋电子器件的设计和优化有关的几个理论问题。我们将研究影响基于超导纳米结构的量子计算机的噪声和退相干的物理来源。我们的目标是控制这些设备固有的缺陷，以便开发大规模容错量子硬件。我们还将研究注入单一或少数顺磁性杂质的硅纳米结构中与自旋相关的输运效应。这项研究旨在优化硅器件中杂质的自旋态到源漏电压的转换，并可能应用于基于硅的量子计算和自旋电子学。另一个要解决的问题是多铁性材料中磁性的电子控制问题。这些材料具有铁电和磁性共存的有序结构，可以有效地对磁性进行栅极控制，从而有可能应用于新型自旋电子器件。

The longstanding progress of conventional semiconductor technology is expected to come to a halt in the next ten to twenty years. As the size of transistors approach the nanometer scale severe problems related to miniaturization and energy dissipation will hinder further improvement of conventional devices. This anticipation is motivating the development of alternative devices that take advantage of the quantum nature at the atomic scale. A notable example is the quantum computer concept, where each bit is formed by a single atom or a group of a few atoms, and the rules of quantum mechanics dictate the way information is processed. Another interesting alternative is spintronics, where the spin of the electrons instead of their charge forms the basis for classical memory and logic, promising much lower rates of energy dissipation per device. This research project addresses several theoretical questions related to the design and optimization of quantum computer and spintronic devices based on semiconductor, superconductor, and magnetic nanostructures. We will investigate the physical origin of noise and decoherence affecting quantum computers based on superconducting nanostructures. Our goal is to control the imperfections inherent to these devices in order to allow the development of large-scale fault-tolerant quantum hardware. We will also study spin-dependent transport effects in silicon nanostructures implanted with a single or a few paramagnetic impurities. This research is oriented towards optimizing the transduction of the spin state of the impurities into a source-drain voltage in a silicon device, with possible applications to silicon-based quantum computation and spintronics. Another problem that will be addressed is the question of electrical control of magnetism in multiferroic materials. These materials possess coexisting ferroelectric and magnetic order, allowing effective gate control of magnetism with possible applications to novel spintronic devices.