By using optical pulses the quantum state of electrons in a semiconductor quantum dot can be manipulated to a large extent in a controlled way. This makes such structures promising candidates for new applications in the fields of optoelectronics, spintronics and quantum information processing. Limitations in the controllability arise due to the coupling of the electrons to the environment, here in particular the coupling to phonons. In this talk I will discuss different optical control scenarios aiming at the generation of specific exciton, phonon or spin states in quantum dot structures.
In the first part I will review some of our recent results on the coupled electron-phonon dynamics in quantum dot structures. The optical excitation of an exciton in the quantum dot is associated with the creation of a lattice displacement, which in turn gives rise to decoherence of the electronic degrees of freedom. I will discuss the role of phonons for state preparation schemes of excitons and biexcitons using resonant, off-resonant or chirped laser pulses. Besides leading to decoherence and relaxation processes, the electron-phonon coupling can also be employed to selectively generate specific phonon quantum states. In particular, I will show that by exciting the quantum dot with a suitable sequence of laser pulses non-classical phonon states like phonon Schrödinger cat states can be generated which, in certain parameter regions, exhibit phonon squeezing.
In the final part I will present recent results on the optical control of the Mn spin state in a quantum dot doped with a single Mn atom. Here the strong exchange coupling of the Mn spin to the spins of electrons and holes allows one to manipulate the Mn spin state via an optical manipulation of the exciton. I will show different protocols, based on suitable sequences of circularly polarized light pulses tuned either to the heavy hole exciton or the light hole exciton transition, that allow one to drive the Mn spin into each of its eigenstates.