G. Ortner

Entangled states of electron–hole complex in a single InAs/GaAs coupled quantum dot molecule

Abstract We summarize here results of calculations and experiments on electron and valence hole states in a single pair of vertically stacked and electronically coupled InAs self-assembled quantum dots. In perfectly aligned quantum dots one can relate an electron–hole complex to a pair of entangled qubits. The information carried by individual qubit is related to the quantum dot index (isospin) of individual carrier. The quality of fabricated quantum dot molecules is identified from the exciton fine structure in a magnetic field.

Non-linear exciton spin-splitting in single InAs/GaAs self-assembled quantum structures in ultrahigh magnetic fields

A. Babinski, G. Ortner, S. Raymond, M. Potemski, M. Bayer, P. Hawrylak, A. Forchel, Z. Wasilewski, and S. Fafard 1 Grenoble High Magnetic Field Laboratory, MPI/FKF and CNRS, BP166, 38042, Grenoble Cedex 9, France 2 Institute of Experimental Physics, Warsaw University, Hoza 69, 00-681 Warsaw, Poland 3 Experimentelle Physik II, Universität Dortmund, D-44221 Dortmund, Germany 4 Institute for Microstructural Sciences, National Research Council, Ottawa, K1A 0R6, Canada and 5 Technische Physik, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany (Dated: November 12, 2018)

Photoluminescence investigations of 2D hole Landau levels in p-type single Al_{x}Ga_{1-x}As/GaAs heterostructures

We study the energy structure of two-dimensional holes in p-type single Al 1 - x Ga x As/GaAs heterojunctions under a perpendicular magnetic field. Photoluminescence measunnents with low densities of excitation power revealrich spectra containing both free and bound-carrier transitions. The experimental results are compared with energies of valence-subband Landau levels calculated using a numerical procedure and good agreement is achieved. Additional lines observed in the energy range of free-carrier recombinations are attributed to excitonic transitions. We also consider the role of many-body effects in photoluminescence spectra.

Entangled exciton states in quantum dot molecules

Abstract The exciton states in self-assembled InAs/GaAs quantum dot molecules have been studied by optical spectroscopy and the results have been compared to detailed theoretical calculations. We demonstrate that excitons in symmetric molecule structures form entangled quantum states with the degree of entanglement controlled by tunneling and Coulomb interaction.

Fine structure of excitons: a sensitive tool for probing the symmetry of self-assembled quantum dots

Abstract We have performed magneto-photoluminescence spectroscopy of self-assembled In(Ga)As/GaAs single quantum dots. Both strength and orientation of the magnetic field have been varied. Symmetry of the dot structures as well as its breaking cause characteristic features in the optical spectra, which are determined by the electron–hole exchange and the Zeeman interaction of the carriers. The symmetry breaking can be either dot inherent due to geometry asymmetries or it can be obtained by applying a magnetic field with an orientation different from the dot symmetry axis.

Electron and Hole States in Vertically Coupled Self‐Assembled InGaAs Quantum Dots

We report results of theoretical and experimental study of optical properties of vertically coupled self‐assembled InGaAs quantum dots. The theoretical calculations include atomistic tight‐binding model in the effective‐bond‐orbital approximation coupled with Peierls substitution to include the magnetic field and with valence‐force‐field model to include strain and piezoelectricity. The single particle states are used to calculate the exciton and biexciton spectra in the exact diagonalization approach. The calculated emission spectra are compared with emission measurements of a single pair of InAs/GaAs vertically coupled quantum dots in a magnetic field.

Experimental indications for coherent coupling of two quantum dots

The coherent coupling of exciton states in single quantum dot molecules has been demonstrated by various experiments. Anti-crossings in the fine structure of excitons have been observed as well as diamagnetic shifts in Faraday- and Voigt-configuration which depend systematically on the width of the barrier between the two dots. Similar systematic dependences have been found for spin-splitting. Further indications have been obtained by comparison of excitation dependent studies of quantum dot molecules and single quantum dots

Magneto-optical studies of 2D hole Landau levels and screening of donor states in p-type modulation doped Ga0.5Al0.5As/GaAs interfaces

We investigated low-temperature photoluminescence from p-type Al1−xGaxAs/GaAs heterostructures subjected to a magnetic field directed perpendicularly to the interface. Two observed type of structure related to interface transitions were interpreted as free (H-band) and donor-bound (D-line) electron recombinations with 2D holes. Properties of both type of structure were explained basing on the results of detailed band-structure calculations. Magnetic field measurements enabled us to examine the binding energy of donor screened by 2D holes in parallel electric and magnetic fields.