Quantum dot spin engineering for quantum optics
BJ Witek · Research Repository (Delft University of Technology) · 2014
1.2.Thesis overview states manifest themselves in the polarization of the exciton emission.The physical intuition behind the Luttinger-Kohn model is developed in order to understand the influence of the quantum dot shape symmetry and strain distribution on the hole spin eigenstates.. Finally, we focus on the properties of light emitted from the quantum dot, in particular its use in the test of the quantum mechanical concept of nonlocality.Chapters 3 to 6 report on the experiments revealing the heavy and light hole excitons properties.In chapter 3 we investigate the heave and light hole spin characteristics that are manifested in the exchange interaction with the electron as well as the Zeeman and diamagnetic interaction in the external magnetic field.Experimental results are shown for highly symmetric GaAs/AlGaAs epitaxial quantum dots, where the hole character can be switched from a dominantly heavy to dominantly light.Further, a comprehensive study of the magnetic properties of the heavy hole exciton is presented in chapter 4. A complete g-factor tensor is revealed thanks to the use of magnetic fields in three different geometries.However, the InAsP quantum dots studied in chapter 4 differ substantially from the quantum dots studied in chapter 3. It is not only a difference in composition, but most importantly in the nanostructure geometry (InP nanowire) and crystal symmetry (wurtzite).In chapter 5 we describe how to engineer a quantum dot system with a light hole ground state using tensile strain.Our first observations of the light hole exciton are shown and compared to the theoretical expectations from the atomistic pseudopotential calculations.Before the growth of quantum dots with high purity light hole ground state was optimized, we went through a series of attempts and characterized quantum dots with mixed hole states.The results of these measurements and the discussion of possible mixing mechanism can be found in chapter 6.From considerations of electron and hole spins in semiconductor quantum dots we move on to an experiment with single photons in chapter 7.In this chapter we describe our attempt to test the quantum non-locality with only one particle: a single photon.Our goal is to show that a single photon can be in a superposition of two distant spatial modes.In order to prove quantum non-locality we implement a Bell measurement in which we probe wave-like properties of a single photon.