Modelling impurity: impurity interactions in silicon and experimental impurity device

硅中的杂质由于其可用量子态的长相干寿命，为量子计算提供了一个很有前途的平台。硅作为微电子工程材料的历史悠久。它可以被提炼到很高的化学纯度，并且在现代经典电子学中使用的微加工技术已经很好地建立起来。为了利用单个掺杂剂的量子特性作为量子比特，单个掺杂剂必须能够与其他掺杂剂相互作用以执行门操作，并且能够被隔离，以便它们可以在操作期间保留其量子信息。为了在硅晶格中引入取代杂质，大面积离子注入是一种方便的方法。然而，这种技术将杂质随机地放置在衬底中，对杂质之间产生的距离控制有限。该体系中杂质之间的量子力学相互作用对近邻距离敏感，因此通过离子注入引入的掺杂剂将具有由潜在点过程描述的近邻距离。该项目将首先探索描述离子注入半导体的最近邻统计数据，以优化有用簇的植入条件，从而使一种杂质的光激发限制另一种杂质之间的相互作用。使用太赫兹辐射的光谱技术将用于大面积离子注入硅器件，以表征杂质本身之间发生的相互作用，以及用于测量器件上光电流的杂质和金属触点之间的相互作用。这个概念将被缩小到制造和研究器件，其光电特性取决于单个植入杂质的电子量子态。这种装置将展示一种在硅中读出量子比特的量子态的方法。

Impurities in silicon provide a promising platform for quantum computing due to the long coherence lifetimes of the available quantum states of the impurities. Silicon has a long pedigree as a material for microelectronic engineering. It can be refined to a high chemical purity and microfabrication techniques used on it in modern classical electronics are well established. To make use of the quantum nature of single dopants as qubits individual dopants must be able to interact with other dopants to perform gate operations and yet be able to be isolated such that they may retain their quantum information over the time of the operation. To introduce substitutional impurities in the silicon lattice, broad area ion implantation is a convenient method. However, this technique places the impurities stochastically in the substrate with limited control over the resulting distance between impurities. The quantum mechanical interactions between impurities in this system are sensitive to nearest neighbour distances therefore dopants introduced via ion implantation will have neighbour distances described by the underlying point processes. This project will begin by exploring the nearest neighbour statistics describing ion-implanted semiconductors looking to optimise implant conditions for useful clusters whereby the optical excitation of one species of impurity gates an interaction between impurities of another species. Spectroscopic techniques using THz radiation will be used on large area ion implanted silicon devices to characterise the interactions occurring between the impurities themselves, and between the impurities and the metal contacts used to measure photocurrent across the device. This concept will be scaled down to fabricate and study device whose photo-electronic properties depends on the electronic quantum state of a single implanted impurity. Such a device would demonstrate a method of quantum state readout of a qubit in silicon.