Time-resolved optical charge sensing for transport measurements on single self-assembled quantum dots

在过去的20年里，固体物理学的驱动力之一是通过在纳米尺度上改变形状和尺寸来控制材料的电子和光学特性。这种可能性是向所谓的著名纳米技术中定制功能材料的范式转变。例如，自组装的砷化铟纳米岛表现得像晶体半导体基质中的人造原子，并已被建立为研究固态环境中类原子特性的理想模型系统。除了对这些量子点的基本物理兴趣之外，他们已经进入了市场（量子点激光器），并且在量子信息处理方面具有远见卓见。在这个研究项目中，单个InAs量子点将被用作纳米尺度上非常敏感的光学电荷探测器。这使得实时研究第二个邻近量子点与导电层之间的载流子动力学成为可能。因此，利用光学探测方案研究了单电子的输运性质。在接近平衡的情况下，可以研究不同电荷纳米岛的量子力学隧穿过程的性质。此外，在单点中制备了电子的非平衡量子态，从而首次可以检测到它们的多粒子自旋和电荷构型，而无需考虑电子-空穴相互作用。这种激发多粒子自旋态的全电制备及其光学检测构成了将量子点用于基于自旋的量子比特的决定性一步。

One of the driving forces in solid-state physics over the last 20 years has been the control over the electronic and optical properties of materials by the variation of shape and size on the nanometer scale. This possibility is a paradigm shift towards tailored functional materials in the so-called and prominent Nanotechnology. As an example, self-assembled indium arsenide Nano-islands behave like artificial atoms in a crystalline semiconductor matrix and have been established as an ideal model system to study atom-like properties in a solid-state environment. Besides the fundamental physical interest in these quantum dots, they have already entered the market (in quantum dot lasers) and have visionary perspectives in quantum information processing.Within this research project, a single InAs quantum dots will be used as a very sensitive optical charge detector on the nanoscale. This makes it possible to study the charge carrier dynamics between a second nearby quantum dot and a conducting layer in real-time. Thus, transport properties of single electrons are studied using an optical detection scheme. The nature of the quantum mechanical tunnelling process of differently charged nano-islands can be investigated in a near-equilibrium situation. Furthermore, non-equilibrium quantum states of the electrons are prepared in the single dot, so that their many-particle spin and charge configurations can be detected for the first time, without the need to take electron-hole interaction into account. This all-electric preparation of excited many-particle spin states and their optical detection constitutes a decisive step towards the use of quantum dots for spin-based quantum bits.