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

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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.