  We demonstrate that the exciton and biexciton emission energies as well as
exciton fine structure splitting (FSS) in single (In,Ga)As/GaAs quantum dots
(QDs) can be efficiently tuned using hydrostatic pressure in situ in an optical
cryostat at up to 4.4 GPa. The maximum exciton emission energy shift was up to
380 meV, and the FSS was up to 180 $\mu$eV. We successfully produced a
biexciton antibinding-binding transition in QDs, which is the key experimental
condition that generates color- and polarization-indistinguishable photon pairs
from the cascade of biexciton emissions and that generates entangled photons
via a time-reordering scheme. We perform atomistic pseudopotential calculations
on realistic (In,Ga)As/GaAs QDs to understand the physical mechanism underlying
the hydrostatic pressure-induced effects.
