  In this work, we present a biexciton state population in (111)B oriented
site-controlled InGaAs quantum dots (QDs) by resonant two photon excitation. We
show that the excited state recombines emitting highly pure single photon pairs
entangled in polarization. The discussed cases herein are compelling due to the
specific energetic structure of Pyramidal InGaAs QDs - an antibinding biexciton
- a state with a positive binding energy. We demonstrate that resonant
two-photon excitation of QDs with antibinding biexcitons can lead to a complex
excitation-recombination scenario. We systematically observed that the resonant
biexciton state population is competing with an acoustic-phonon assisted
population of an exciton state. These findings show that under typical
two-photon resonant excitation conditions deterministic biexciton state
initialization can be compromised. This complication should be taken into
account by the community members aiming to utilise similar epitaxial QDs with
an antibinding biexciton.
