M.A. Müller

Phonon-assisted robust and deterministic two-photon biexciton preparation in a quantum dot

We investigate both experimentally and theoretically a simple yet more robust and flexible alternative to Rabi oscillation-type biexciton preparation protocols traditionally used for semiconductor quantum dots. The quantum dot is excited by a strong laser pulse positively detuned from the two-photon resonance yielding an on demand initialization of the biexciton state by making use of the phonon-induced thermalization of the photon dressed states. It is shown that for excitation pulses in the picosecond range, a stable and high fidelity of up to

Polarization-entangled photons from an InGaAs-based quantum dot emitting in the telecom C-band

f_{XX}=0.98\pm 0.01

Cavity-assisted simultaneous dressing of biexciton and exciton transitions in a single quantum dot

is reached. Notably, the generated photons show similar coherence properties as measured in the resonant two-photon scheme. This protocol is a powerful tool for the control of complex solid state systems combining radiative cascades, entanglement and resonant cavity modes.

Identification of Vacancies on each Sublattice of SiC by Coincident Doppler Broadening of the Positron Annihilation Photons after Electron Irradiation

We demonstrate the emission of polarization-entangled photons from a single semiconductor quantum dot in the telecom C-band (1530 nm–1565 nm). To reach this telecommunication window, the well-established material system of InAs quantum dots embedded in InGaAs barriers is utilized with an additional insertion of an InGaAs metamorphic buffer to spectrally shift the system to the desired wavelengths. For the observation of polarization-entangled photon pairs, the biexciton-exciton cascade of a quantum dot displaying an intrinsically low fine-structure splitting is investigated by means of polarization-dependent cross-correlation measurements. A complete set of tomography measurements enables us to reconstruct the two-photon density matrix and therefore to calculate a corresponding fidelity f+ to the maximally entangled Bell state Ψ+ of 0.61 ± 0.07, a concurrence of 0.74 ± 0.11, a tangle of 0.55 ± 0.14, and a negativity of 0.63 ± 0.12, clearly proving the entanglement of the states. Finally, the development o...

Thermal vacancy formation and D03 ordering in nanocrystalline intermetallic (Fe3Si)95Nb5

We introduce the regime of simultaneous dressing of the biexciton-exciton and exciton-ground transitions in a single quantum-dot cavity system. The formation of pump-induced dressed states is explained theoretically and demonstrated experimentally using photoluminescence measurements.