Engineering Future Quantum Technologies in Low-Dimensional Systems

低维系统中的未来量子技术工程

• 批准号: MR/X006077/1
• 负责人: Sanjeev Kumar
• 金额: $ 75.82万
• 依托单位: University College London
• 依托单位国家: 英国
• 项目类别: Fellowship
• 财政年份: 2024
• 资助国家: 英国
• 起止时间: 2024 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=MR%2FX006077%2F1
• 关键词: Engineering; Future; Quantum; Technologies; Low

Quantum transport in low-dimensional semiconductor nanostructures is a well-established field of research that has resulted in several landmark discoveries in solid-state physics over the past several decades. Among various findings, the one which stands out is the discovery of the Quantum Hall Effect (QHE) in 1980. The QHE was the first experimental demonstration of the quantum nature of the celebrated classical Hall effect. In the QHE, the transverse conductance of a two-dimensional electron gas is represented as (e^2/h).v, where v is the filling factor. The conductance shows remarkably flat plateaus for integer values of the filling factor. It may be noted that the transverse conductance or QHE is proportional to fundamental constants (e^2/h), and does not depend on the sample geometry or size, so is invariant. A pioneering theorist, R Laughlin proposed a theory describing the integer states in terms of a topological invariant, Chern number. In 1982, physicists working at Bell labs reported in the QHE measurements that new quantised plateaus appeared at fractional values of the filling factor, like 1/3. This remarkable discovery gave birth to the Fractional Quantum Hall Effect (FQHE). The observation was due to electron-electron interactions in the two-dimensional electron gas in high-quality semiconductors under the influence of a strong quantising magnetic field. FQHE was the first demonstration in solid state physics that the quasiparticles formed at the extremely high magnetic field and very low temperatures would possess a fraction of an electronic charge, say, 1/3. Following the discovery of the FQHE, several experimental studies resulted in the discovery of more than 100 new fractional states. While FQHE/QHE was receiving considerable attention in the 80s, an exciting development took shape when Haldane in 1988 proposed the idea of QHE without any magnetic field using the tight-binding model on a honeycomb lattice. He suggested that the existence of quantum Hall states do not necessarily require an external magnetic field, but depends on the symmetries of the system and its topological phases. This important contribution to the knowledge led to various discoveries, including the anomalous and Hall effects and topological insulators. It was shown in 1988 that conductance through a one-dimensional channel was quantised as (2e^2/h). N, where N is an integer. This was a remarkable observation and one of the significant discoveries in solid-state physics, that the conductance of 2D electrons, when confined to one dimension would quantise in units of fundamental constants (2e^2/h), a behaviour similar to the QHE although without any magnetic field. As FQHE was complementing the IQHE when electron-electron interactions were introduced, physicists wondered if there could be a fractional counterpart of the 1D integer conductance quantisation. This critical question in experimental physics remained unanswered until 2018/2019, when electrons in high-quality semiconductors based on GaAs showed fractional conductance quantisation in units of e^2/h at values 2/5,1/6, 1/2, etc. These new quantum states form when electrons in a 1D channel configure into a zigzag, enabling "ring paths" and "cyclic currents". These complex quantum phenomena result in fractional excitations which show promise for topological quantum computing schemes. This proposal aims to investigate the fractional quantum states formed in weakly confined 1D quantum wires, where several parameters play a significant role in achieving this unexpected quantum behaviour. We aim to investigate the nature of these new fractional quantum states and how their spin and charge phases could be measured and manipulated. These novel quantum states would be utilised to investigate entanglement via Aharonov-Bohn interferometry, spin blockage phenomena, fractional state selection via electron focusing, electronic charge via quantum shot noise measurements, etc.

低维半导体纳米结构中的量子运输是一个完善的研究领域，在过去的几十年中，在固态物理学中发现了一些具有里程碑意义的发现。在各种发现中，突出的发现是1980年发现量子大厅效应（QHE）。在QHE中，二维电子气体的横向电导表示为（e^2/h）.v，其中v是填充因子。电导显示了填充因子整数值的平坦高原。可以注意到，横向电导或QHE与基本常数（E^2/H）成正比，并且不依赖于样品几何或大小，因此不变。 R Laughlin是一位开创性的理论家，提出了一种理论，描述了整数状态的拓扑不变，Chern数字。 1982年，在Bell Labs工作的物理学家在QHE测量中报道了新的定量高原出现在填充因子的分数中，例如1/3。这一出色的发现诞生了分数量子厅效应（FQHE）。该观察结果是由于在强量化磁场的影响下，高质量半导体中二维电子气体中的电子电子相互作用引起的。 FQHE是固态物理学中的第一次演示，即在极高的磁场处形成的准颗粒，并且温度非常低的电子电荷将具有1/3的电子电荷。在发现FQHE之后，一些实验研究导致发现了100多个新的分数状态。尽管FQHE/QHE在80年代受到了很大的关注，但当Haldane在1988年提出了QHE的想法而没有任何磁场的想法时，使用蜂窝状晶格上的紧密结合模型就形成了令人兴奋的发展。他认为，量子厅状态的存在不一定需要外部磁场，而是取决于系统的对称性及其拓扑阶段。对知识的这一重要贡献导致了各种发现，包括异常和霍尔效应以及拓扑绝缘子。 1988年，人们表明，通过一维通道的电导为（2e^2/h）。 n，n是整数。这是一个了不起的观察结果，并且是固态物理学中的重要发现之一，即2D电子的电导限制在一个维度上时，将以基本常数（2E^2/h）的单位进行量化，这种行为类似于QHE，尽管没有任何磁场。当引入电子电子相互作用时FQHE正在补充IQHE时，物理学家想知道是否可能存在1D整数电导定量的分数对应物。 This critical question in experimental physics remained unanswered until 2018/2019, when electrons in high-quality semiconductors based on GaAs showed fractional conductance quantisation in units of e^2/h at values 2/5,1/6, 1/2, etc. These new quantum states form when electrons in a 1D channel configure into a zigzag, enabling "ring paths" and "cyclic currents".这些复杂的量子现象导致分数激发，这对拓扑量子计算方案显示出希望。该建议旨在研究在弱限制的1D量子线中形成的分数量子状态，其中几个参数在实现这种意外的量子行为中起着重要作用。我们旨在研究这些新的分数量子状态的性质，以及如何测量和操纵它们的旋转和电荷相。这些新颖的量子状态将用于通过Aharonov-Bohn干涉法，自旋阻塞现象，通过电子聚焦的分数态选择，通过量子射击噪声测量值进行电子电荷等研究纠缠的。