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/S015728/1
• 负责人: Sanjeev Kumar
• 金额: $ 133.58万
• 依托单位: University College London
• 依托单位国家: 英国
• 项目类别: Fellowship
• 财政年份: 2019
• 资助国家: 英国
• 起止时间: 2019 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=MR%2FS015728%2F1
• 关键词: Engineering; Future; Quantum; Technologies; Low

Classically electrons in a three-dimensional solid can change their momentum in all possible directions. However, electrons in semiconductors can be manipulated so that they are constrained to move in lower dimensions. One of the perfect examples of such a system is a semiconductor heterostructure of GaAs/AlGaAs forming a plane of electrons, only a few nanometer thick, at its junction where electrons possessing quantised energy and freedom to change momentum in the plane. Such remarkable ensemble of non-interacting electrons is known as the two-dimensional electron gas (2DEG). The electrons in a 2DEG system are highly mobile and at low temperatures their motion is mainly scattering free due to the reduction in the interaction with lattice vibrations (phonons) and there is little impurity scattering. When the 2D electrons are electrostatically squeezed to form a narrow, 1D channel whose effective size is less than the electron mean free path for scattering then quantum phenomena associated with the electrons becomes resolved. In this situation, the energy of 1D electrons becomes quantised and discrete levels are formed. At a low carrier concentration of electrons, if the potential which is confining the 1D electrons is relaxed then electrons can arrange themselves into a periodic zig- zag manner forming a Wigner Crystal, named after Wigner who first predicted such a phenomenon in metal in 1936. Recently the distortion of a line of electrons into a zig-zag and then into two separate rows of electrons was observed and associated rich spin and charge phases. A very subtle change in confinement can result in two rows emerging from a zig-zag state which indicates that there is a narrow range where wavefunctions separate and form entangled states. Entanglement is a remarkable phenomenon in which a change in state of one electron will introduce a change in state of another. This amazing property forms the basis for quantum information processing with practical consequences related to quantum technologies, which will be investigated in this proposal. Another most important aspect of my Fellowship proposal is investigating the zig-zag regime or relaxed 1D system in search of fractional quantum states in the absence of a magnetic field. In the presence of a large magnetic field the energy of a 2DEG is quantized to form Landau levels which gave rise to two celebrated discoveries of the Integer and fractional quantum Hall effects in 1980 and 1982 respectively. Such unexpected revelations then pose a question whether fractional quantised states in the absence of any magnetic field in any lattice or topological insulators could ever be observed? However, there were no reports of observations of any fractional states without a magnetic field until the recent discovery of fractional charges of e/2 and e/4 arising from the relaxed zig-zag state in a Germanium-based 1D system. The proposal is inspired by this and the recent experimental finding of non-magnetic self-organised fractional quantum states in tradition GaAs based 1D quantum wires, which was completely unanticipated. The research aim is to introduce new insights, and new aspects of quantum physics, by exploiting the interaction effects in low-dimensional semiconductors by manipulating electron wavefunctions in a controllable manner to allow technological exploitation of basic quantum physics. The major challenges to be investigated: spin and charge manipulation, demonstrating electron entanglement and detection, mapping self-organised fractional states and their spin states, controlled manipulation and detection of hybrid fractional states and establishing if they are entangled. This research proposal opens up a new area in the quantum physics of condensed matter with the generation of Non-Abelian fractions which can be used in a Topological Quantum Computation scheme.

在三维固体中的经典电子可以在所有可能的方向上改变其动量。但是，可以操纵半导体中的电子，以使其受到限制以较低的尺寸移动。这种系统的完美示例之一是GAAS/ALGAA的半导体异质结构，形成一个电子平面，仅在其交界处只有少数纳米厚的电子厚度，在那里具有定量能量和自由度在平面中改变动量的电子。这种非相互作用电子的显着合奏称为二维电子气体（2DEG）。 2DEG系统中的电子高度流动性，在低温下，由于与晶格振动（声子）的相互作用减少，并且几乎没有杂质散射，因此它们的运动主要不散射。当将2D电子静电挤压以形成一个狭窄的1D通道时，其有效尺寸小于散射的电子平均自由路径，然后与电子相关的量子现象解析。在这种情况下，一维电子的能量被定量并形成离散水平。在低载体浓度的电子浓度下，如果限制了1D电子的电势会放松，那么电子可以将自己安排成一个周期性的曲折方式，形成了wigner晶体，以Wigner的名字命名，以Wigner的名字命名，Wigner在1936年首先预测了这种现象在1936年的金属中。最近，将电子线的变形变成了Zig-Zag和Elect and Elect and Elect and Elect and Elect and Electer and Electer and Electer and Electer and of Electer and of Electer and of of Electer and of sows of sows of sows。限制的非常微妙的变化可能会导致从锯齿形状态出现了两排，这表明在波形分离并形成纠缠状态的狭窄范围内。纠缠是一种了不起的现象，在这种现象中，一个电子状态的变化将引入另一个电子状态的变化。这种惊人的属性构成了量子信息处理的基础，并与量子技术有关的实际后果，这将在本提案中进行研究。我的奖学金提案的另一个最重要方面是调查锯齿形策略或放松的1D系统，以在没有磁场的情况下寻找分数量子状态。在存在大磁场的情况下，将2DEG的能量量化以形成Landau水平，从而在1980年和1982年分别引起了两个著名的整数和分数量子霍尔效应的著名发现。然后，这种意外的启示提出了一个问题，是否可以观察到在任何晶格或拓扑绝缘子中没有任何磁场的情况下，是否可以观察到分数定量状态？但是，直到最近发现E/2的分数电荷和E/4的分数电荷在基于也基的一维系统中引起的，没有任何没有磁场的分数状态的报道。该提案的灵感来自于此，以及最近在传统GAAS的一维量子线中对非磁性自组织的分数量子状态的实验发现，这是完全意外的。研究的目的是通过以可控的方式操纵电子波形来允许对基本量子物理学的技术利用来利用低维半导体中的相互作用效应，从而引入量子物理学的新见解和新方面。要研究的主要挑战是：旋转和电荷操纵，证明电子纠缠和检测，绘制自组织的分数状态及其旋转状态，控制和检测杂交分数状态并确定它们是否纠缠。这项研究提案为凝结物质的量子物理学开辟了一个新区域，并产生了非亚伯分数的生成，可以在拓扑量子计算方案中使用。

项目成果

Resistance hysteresis in the integer and fractional quantum Hall regime

整数和分数量子霍尔体系中的电阻滞后

• DOI: 10.1103/physrevb.107.205307
• 发表时间: 2023
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: Peraticos E

Nonequilibrium phenomena in bilayer electron systems

双层电子系统中的非平衡现象

• DOI: 10.1103/physrevb.107.l041302
• 发表时间: 2023
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: Shevyrin A

Hall resistance anomalies in the integer and fractional quantum Hall regime

• DOI: 10.1103/physrevb.102.115306
• 发表时间: 2020-09
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: E. Peraticos;Sanjeev Kumar;M. Pepper;A. Siddiki;I. Farrer;D. Ritchie;G. Jones;J. Griffiths

Interactions and non-magnetic fractional quantization in one-dimension.

• DOI: 10.1063/5.0061921
• 发表时间: 2021-09-13
• 期刊: Applied physics letters
• 影响因子: 4
• 作者: Kumar S;Pepper M
• 通讯作者: Pepper M

Engineering electron wavefunctions in asymmetrically confined quasi one-dimensional structures

非对称约束准一维结构中的工程电子波函数

• DOI: 10.1063/5.0045702
• 发表时间: 2021
• 期刊: Applied Physics Letters
• 影响因子: 4
• 作者: Kumar S