Control and manipulation of charge and spin in single and coupled quantum dots

I will discuss measurements of the spin lifetime in self-assembled InGaAs dots in GaAs. The spin relaxation time (T$_{1})$ is found to be extremely long (e.g. $>$25ms at T=1K, B=4T) decreasing with magnetic field according roughly to a clear B$^{-4}$ power law [1]. Furthermore, T$_{1}$ is found to reduce linearly with lattice temperature and be very strongly sensitive to the motional quantisation (s-p shell splitting). Another topic is the the coherent quantum coupling of a vertically stacked pair of quantum dots. The interaction can be tuned in such quantum dot molecule devices using an applied voltage as external parameter [2]. At the resonance the electron component of the exciton wave function hybridizes, giving rise to a quantum coupling energy in the excitonic spectrum. This work is supported financially by Deutsche Forschungsgemeinschaft via collaborative research center 631 and by German Federal Ministry of Research via NanoQuit. [1] M. Kroutvar, Y. Ducommun, D. Heiss, D. Schuh, M. Bichler, G. Abstreiter and J. J. Finley. Nature\textbf{ 432}, 81 (2004) [2] H. J. Krenner, E. C. Clark, A. Kress, D. Schuh, M. Bichler, G. Abstreiter and J.J. Finley. PRL \textbf{94}, 057402 (2005)