Nanoelectronic Based Quantum Physics- Technology and Applications.

流经半导体器件的电子在现代生活中具有极其重要的意义。当器件足够小，以至于其中一个维度处于纳米级时，电子的量子性质就变得突出起来，必须详细考虑。在极低的温度下工作可以减少相互的电子-电子散射，并导致电子传输的波状性质在超过器件大小的距离内变得可见。使用比波函数的相干长度或杂质散射事件之间的距离更小的设备进行的实验，已经允许观察到一系列量子效应。近年来，理论提出，“量子计算机”比传统计算机有一定的优势，因为它们允许大规模并行操作模式。这是基于量子原理，因此，如果两个电子处于量子态，那么它们的总自旋波函数反映了可能存在的态的范围。正是这种状态的叠加，才是量子计算机的基础。它是一种纯粹的量子现象，并产生了“薛定谔猫”之类的概念，这些概念体现了量子力学的非直觉性。另一个可能导致新技术应用的性质是显著的纠缠。这种纯粹的量子效应会导致两个电子处于相同的量子态，并“知道”彼此的存在，因此，如果一个电子的自旋发生旋转，那么另一个电子的自旋就会受到影响，尽管它们之间存在着相当大的距离。在这项工作中，我们提议利用半导体纳米结构来发现新的量子效应，并将它们结合起来，创建用于实际开发的集成量子电路。该项目综合了理论、半导体生长/制造和三个不同中心的测量，其初始目标是设计和制造用于后续集成的关键量子组件。量子泵是量子泵的主要组成部分，它可以以非常高的精度在高频下传输受控数量的电子。这种装置可以用来产生纠缠电子，然后可以进行研究和使用。另一个重要的部件是光学中偏振分束器的电子类比，在这里，通过使用局域电子自旋，传入的电子要么被传输，要么被反射，取决于它的自旋方向。我们还建议利用自旋-轨道耦合，允许在纳米结构中建立自旋极化电流，然后将其用于量子器件。此外，还建议使用间接电子相互作用机制在不同器件之间传输自旋信息。在这方面可能具有新特性的一个系统是初始Wigner晶格，它可以在一条电子被弱限制时形成，并且电子-电子斥力的最小化迫使电子形成两个单独的行。在这里，它们可以被纠缠，并以一种与泵浦互补的方式构成连续的纠缠电子供应。新型量子组件将被开发出来。然后它们将被集成，形成一种早期类型的电路，其中量子效应主导性质。它的目的是开发基本的量子处理器，特别是CNOT门，在这种门中，一个电子的自旋根据另一个电子的自旋方向旋转。除这些目标外，一些附带成果将对其他领域产生影响。例如，有必要开发在1毫升开尔文的超低温下测量电子性质的技术，而要开发的自旋极化电流将在重要的自旋电子学领域中得到应用。

Electrons flowing through semiconductor devices are of immense importance in modern life. When devices are made sufficiently small, such that one of the dimensions is in the nanometre regime, the quantum nature of the electron comes to the fore and must be considered in detail. Working at very low temperatures reduces the mutual electron-electron scattering and results in the wave nature of electron transport becoming observable over distances which can exceed the size of the device. Experiments using devices which are smaller than the coherence length of the wavefunction, or the distance between impurity scattering events, have allowed observation of a range of quantum effects.In recent years theories have proposed that a "quantum computer" has certain advantages over conventional computers as they allow a massively parallel mode of operation. This is based on quantum principles, thus if two electrons are in a quantum state then their total spin wavefunction reflects the range of possible states that can be present. It is this superposition of states which is the basis of a quantum computer. It is a purely quantum phenomenon and has given rise to concepts such as "Schrodinger's Cat" which exemplify the non-intuitive nature of quantum mechanics. Another property which could give rise to new technological applications is the remarkable entanglement. This purely quantum effect results in two electrons being in the same quantum state and "knowing" about each other's existence, consequently if the spin of one is rotated then the spin of the other is affected despite there being a considerable distance between them.In this work we propose to utilise semiconductor nanostructures to find new quantum effects and combine them to create integrated quantum circuits for practical exploitation. The project integrates theory, semiconductor growth/fabrication and measurements in three different centres, it has as initial targets the design and fabrication of key quantum components forsubsequent integration. A principal component is the Quantum Pump which can transmit controlled numbers of electrons at high frequencies with very high accuracy. This device can be used for the generation of entangled electrons which can then be investigated and put to use. Another component which is of importance is the electronic analogy of the polarising beam splitter in optics, here by using localised electron spins an incoming electron is either transmitted or reflected depending on its spin direction. We also propose to exploit the spin-orbit coupling which allows a spin polarised current to be established in a nanostructure which can then be utilised in a quantum device.It is further proposed to build on the use of an indirect electron interaction mechanism to transmit spin information between different devices. A system which may have novel properties in this regard is the incipient Wigner lattice which can form when a line of electrons is weakly confined and minimisation of the electron-electron repulsion forces the electrons to form two separate rows. Here they can be entangled and constitute a continuous supply of entangled electrons in a manner which is complementary to the pump.New types of quantum components will be developed. They will then be integrated to form an early type of circuit in which quantum effects dominate the properties. It is intended to develop basic quantum processors in particular a CNOT gate in which the spin of an electron is rotated depending on the direction of the spin of another. In addition to these objectives a number of spin-off achievements will have an impact on other fields. For example it will be necessary to develop techniques of measurement of electronic properties at ultra low temperatures, 1 milliKelvin, and the spin polarised currents to be developed will have applications in the important field of spintronics.