Real-Time Electron Dynamics in Nanoscale Structures

纳米尺度的电学结构显示出许多有趣的现象，如库仑阻塞或量子相干。这种现象传统上是使用直流或准直流测量技术来研究的，即使潜在的电子动力学发生在更短的时间尺度上。虽然这样的测量提供了大量的信息，但通过研究单个电子的动力学可以获得更多的信息。例如，电子隧穿中的时间关联预计会在库仑阻塞纳米结构中传输，但从来没有直接观察到。个人研究人员奖支持一个项目，该项目通过使用射频单电子晶体管来研究量子点中单个电子的运动来解决这些问题。这样做最终将使人们能够在数十到数百纳秒的时间尺度上研究电子关联和量子相干。将对单量子点和双量子点进行一系列实验，目的是通过它们的计数统计来研究电子关联，并探索它们内在时间尺度上的量子相干现象。这些实验中使用的技术也与量子计算中的量子比特读出问题相关，并有望在总体上阐明量子测量问题。这项工作涉及使用纳米制造和射频表征方面的尖端技术，以及低温和低噪音技术，为学生提供在学术或工业中有价值的技能。对于许多纳米级结构(其物理尺寸以十亿分之一米为单位测量)，单个电子的运动对其电学特性起着重要的作用。虽然单个电子的作用和它们之间的相互作用早已被认识到，但纳米结构中的电子输运通常是通过测量平均电导来探测的。虽然这种测量提供了大量的信息，但通过研究单个电子的动力学可以获得更多的信息。个人研究人员奖支持一个项目，该项目通过使用被称为射频单电子晶体管的快速且非常灵敏的静电计来研究半导体量子点上单个电子的运动来解决这些问题。例如，通过观察单个电子在通过点的电流中的运动，就有可能提取关于电子如何在纳米结构中相互作用的额外信息。由于电子是量子力学对象，研究还将重点放在观察电子运动的过程如何影响运动本身。这个问题对于量子计算中量子比特的测量也很重要，它涉及到量子力学物体在受到宏观物体影响时如何失去其波状性质(量子相干性)的问题。在短时间尺度(百万分之一秒或更少)上测量单个电子的能力应该会为这些问题带来新的曙光。这项工作涉及使用纳米制造和射频表征方面的尖端技术，以及低温和低噪音技术，为参与其中的学生提供在学术界或工业中有价值的技能。

Nanoscale electrical structures exhibit numerous interesting phenomena such as the Coulomb blockade or quantum coherence. Such phenomena have traditionally been studied using dc or quasi-dc measurement techniques, even though the underlying electron dynamics take place on much shorter time scales. While such measurements provide a tremendous amount of information, much more could be accessed by studying the dynamics of individual electrons. For instance, temporal correlations in electron tunneling are expected in transport through Coulomb blockade nanostructures, but have never been observed directly. This Individual Investigator Award supports a project that addresses such issues by using a radio-frequency single-electron transistor to study the motion of individual electrons in a quantum dot. Doing so will ultimately allow investigation of electronic correlations and quantum coherence on time scales of tens to hundreds of nanoseconds. A series of experiments on both single and double quantum dots will be undertaken, with the goal of studying electron correlations by means of their counting statistics and probing quantum coherent phenomena on their intrinsic time scales. The techniques used in these experiments are also relevant to the qubit readout problem in quantum computation, and are expected to shed light on the quantum measurement problem in general. This effort involves use of cutting-edge techniques in nanofabrication and radio-frequency characterization, as well as cryogenic and low noise techniques, providing the students involved with skills valuable in either academia or industry.For many nanoscale structures (whose physical dimensions are measured in billionths of a meter), the motion of individual electrons plays an important role in their electrical characteristics. While the roles of individual electrons and the interactions between them have long been recognized, electrical transport in nanostructures is usually probed by measuring the average conductance. Although such measurements have provided a tremendous amount of information, much more could be accessed by studying the dynamics of individual electrons. This Individual Investigator Award supports a project that addresses such issues by using a fast and very sensitive electrometer known as a radio-frequency single electron transistor to study the motion of individual electrons on a semiconductor quantum dot. By observing the motion of individual electrons in a current driven through the dot, for instance, it will be possible to extract additional information about how electrons interact in nanostructures. Because electrons are quantum-mechanical objects, the research will also focus on how the process of observing the electron motion affects the motion itself. This problem, which is also important for measurement of a qubit in quantum computation, is related to the question of how quantum mechanical objects lose their wave-like properties (their quantum coherence) when affected by a macroscopic object. The ability to measure individual electrons on short time scales (millionths of a second or less) should shed new light on such issues. This effort involves use of cutting-edge techniques in nanofabrication and radio-frequency characterization, as well as cryogenic and low noise techniques, providing the students involved with skills valuable in either academia or industry.