  Semiconductor quantum dots (QDs) have potential applications in quantum
information processing due to the fact that they are potential on-demand
sources of single and entangled photons. Generation of polarization-entangled
photon pairs was demonstrated using the biexciton-exciton radiative cascade.
One obvious way to increase the number of quantum correlated photons that the
QDs emit is to use higher-order multiexcitons, in particular the triexciton.
Towards achieving this goal, we first demonstrate deterministic generation of
the QD-confined triexciton in a well-definedcoherent state and then spectrally
identify and directly measure a three-photon radiative cascade resulting from
the sequential triexciton-biexciton-exciton radiative recombination.
