Spin Physics
Over the past few years the search for prototype systems that will allow us to build a quantum computer has attracted the interest of many research groups around the world. This interest is primarily driven by the constantly increasing need for high processing power. One of the main requirements for implementation of the quantum information processing is the availability of scalable physical systems with well defined quantum states which can be used as quantum bits, or as they are often termed qubits. Click for more details
Following the above mentioned requirements for implementation of the quantum computation the Spin Physics subgroup is investigating the properties of confined charges in self-assembled quantum dots and the arising spin related phenomena. Experiments were performed in which in small ensembles of InGaAs self-assembled quantum dots electrons and holes with predetermined spin orientation were initialized, stored and later detected utilizing the optical selection rules for absorption of photons in self-assembled quantum dots.
Schematic of a spin readout scheme. The individual steps are: reset by fast electron tunneling, charging with resonant excitation followed by hole tunneling, spin manipulation with, e.g., microwave pulses, spin to charge conversion by spin-conditional resonant absorption, and charge readout via non-resonant photoluminescence.
The present work is focused on scaling down the previous experiments on a single dot level, which is clearer and more controllable system. This resulted in the development of a novel approach toward investigation of the spin properties of a single confined charge carrier in a single self-assembled quantum dots.
The figure above depicts schematically the measurement scheme when applied to electrons.
Employing this novel spin read-out scheme we have achieved all optical preparation and readout of a single electron spin in an individual self-assembled quantum dot. The methods combine spin to charge conversion with luminescence recycling and are applied to optically probe the spin relaxation dynamics. Importantly, our approach allows us to probe the dynamics of a single spin over ultra long timescales (≥200μs), generally inaccessible to optical single spin readout.
Selected Publications
Funding
We gratefully acknowledge funding from:
- the German Science Foundation via SFB631 - Project C6
- Nanosystems Initiative Munich (NIM)