Electron Self-Organisation and Applications

电子自组织及其应用

• 批准号: EP/J013153/1
• 负责人: Michael Pepper
• 金额: $ 109.45万
• 依托单位: University College London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2012
• 资助国家: 英国
• 起止时间: 2012 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FJ013153%2F1
• 关键词: Electron; Self; Organisation; Applications

In most situations electrons in semiconductors can be regarded as free with their energy determined by their total number and their effective mass with the mutual repulsion only slightly modifying this free electron picture. However at low values of carrier concentration the repulsion can dominate the manner in which the electrons diffuse in the solid, a voluminous amount of theory has shown that at sufficiently low temperatures the electrons can arrange themselves into a crystalline ensemble. This is termed a Wigner Crystal, or Wigner Lattice, after Wigner who first predicted such a phenomenon, it has proved rather difficult to observe as the observation of a regular structure is not simple and often the predictions of theory are not found due to the presence of disorder. In one dimension the electrons form a single line and the Wigner Crystal is the trivial case of the electrons seeking a regular periodicity. However, as the confinement weakens, or the electron repulsion increases, so it is possible for the line of electrons to distort as electrons attempt to maximise their separation. In the limit the row splits into two separate rows. The experimental system for such investigations is the electron gas in the GaAs-AlGaAs heterostructure grown by Molecular Beam Epitaxy and the samples are fabricated using high resolution electron beam lithography. In these samples it is possible to control the confinement potential by patterned gates to which voltages are applied, when the samples are sufficiently short electrons drift through ballistically which is without being scattered by random impurities or defects. In this regime the conductance of a one-dimensional wire takes a value 2e2/h where the factor of 2 arises from the spin degeneracy, e is the electron charge and h is Planck's constant. Consequently when a row of electrons splits into 2 rows a conductance of 4e2/h is observed as the ground state. By following the values of conductance as the confinement is changed so the movement of energy levels can be obtained as a function of confinement potential. This has been observed and we call the two rows formed as a result of the electron-electron repulsion the Incipient Wigner Lattice, IWL.Analysis of the results on the movement of energy levels has shown that prior to the formation of the two separate rows a hybridised state is formed in which two electrons are shared between the two rows such that they form a distorted single row. Quantum Mechanics dictates that two electrons shared in this way must have opposite spins and they can be entangled as a consequence of which they each "know" the quantum state the other is in. Entanglement is a remarkable phenomenon in which if the electrons are separated but still entangled then a change of state of one will produce a change in the state of the other. This remarkable property lies at the heart of many proposals for quantum information processing and quantum logic and may give rise to practical consequences not yet envisaged.In this research project we propose to study the IWL and optimise the creation of the hybrid state in which the electrons are entangled. Once this state is completely understood the properties of entangled electrons will be studied by injecting them from the IWL into other quantum structures which essentially form an early quantum integrated circuit. One of the characteristics of entangled electrons is that if two of them are in this state then a variation of the wavelength of them is effectively doubled compared to a single electron. Consequently if we perform an interference experiment there is an immediate difference between the behaviour of entangled and normal electrons, this is the effect which we will explore. The ultimate objective of the work is to develop a method of delivering a stream of entangled electrons and then demonstrate the entanglement in a series of integrated quantum devices with a view to their practical application

在大多数情况下，半导体中的电子可以被视为自由电子，其能量由它们的总数和有效质量决定，相互排斥仅稍微改变这个自由电子图。然而，在载流子浓度较低的情况下，排斥力会主导电子在固体中扩散的方式，大量理论表明，在足够低的温度下，电子可以将自己排列成晶体整体。这被称为维格纳晶体或维格纳晶格，以维格纳首次预测这种现象而得名，事实证明观察这种现象相当困难，因为规则结构的观察并不简单，并且由于存在而常常无法发现理论的预测的混乱。在一维中，电子形成单线，维格纳晶体是电子寻求规则周期性的简单情况。然而，随着限制的减弱或电子排斥力的增加，当电子试图最大化它们的分离时，电子线可能会扭曲。在限制中，该行分成两个单独的行。此类研究的实验系统是通过分子束外延生长的 GaAs-AlGaAs 异质结构中的电子气，并且使用高分辨率电子束光刻技术制造样品。在这些样品中，当样品足够短时，可以通过施加电压的图案化栅极来控制限制电势，电子以弹道方式漂移通过，而不会被随机杂质或缺陷散射。在这种情况下，一维导线的电导值为 2e2/h，其中因子 2 由自旋简并性产生，e 是电子电荷，h 是普朗克常数。因此，当一行电子分裂成 2 行时，观察到的基态电导为 4e2/h。通过跟踪限制变化时的电导值，可以获得作为限制势函数的能级移动。这已经被观察到，我们将由于电子-电子排斥而形成的两行称为初始维格纳晶格，IWL。对能级运动结果的分析表明，在形成两行独立的行之前形成杂化状态，其中两个电子在两行之间共享，从而形成扭曲的单行。量子力学规定，以这种方式共享的两个电子必须具有相反的自旋，并且它们可以纠缠，因此它们每个“知道”另一个所处的量子态。纠缠是一种显着的现象，其中如果电子分离但仍然纠缠在一起，那么一个人的状态的改变将导致另一个人的状态的改变。这一显着的特性是量子信息处理和量子逻辑的许多建议的核心，并且可能会产生尚未设想的实际后果。在这个研究项目中，我们建议研究 IWL 并优化电子混合态的创建被纠缠。一旦完全理解了这种状态，就可以通过将纠缠电子从 IWL 注入到其他量子结构中来研究纠缠电子的特性，这些量子结构基本上形成了早期的量子集成电路。纠缠电子的特征之一是，如果其中两个处于这种状态，那么与单个电子相比，它们的波长变化实际上加倍。因此，如果我们进行干涉实验，纠缠电子和正常电子的行为之间会存在直接差异，这就是我们将探索的效果。这项工作的最终目标是开发一种传递纠缠电子流的方法，然后在一系列集成量子器件中演示纠缠，以期实现其实际应用