  Precise positioning of single site-controlled inverted pyramidal InGaAs QD at
the antinode of a GaAs photonic crystal cavity with nanometer-scale accuracy
holds unique advantages compared to self-assembled QDs and offers great promise
for practical on-chip photonic quantum information processing. However, the
strong coupling regime in this geometry has not yet been achieved due to the
low cavity Q-factor based on the (111)B-oriented membrane structures. Here, we
reveal the onset of phonon-mediated coherent exciton-photon interaction on our
tailored single site-controlled InGaAs QD - photonic crystal cavity. Our
results present a Rabi-like oscillation of luminescence intensity between
excitonic and photonic components correlated with their energy splitting
pronounced at small detuning. Such Rabi-like oscillation is well reproduced by
modeling the coherent exchange of the exciton-photon population. The modeling
further reveals an oscillatory two-time covariance at QD-cavity resonance,
which indicates that the system operates at the onset of the strong coupling
regime. Moreover, by using the cavity mode as a probe of the virtual state of
the QD induced by phonon scattering, it reveals an increase in phonon
scattering rates near the QD-cavity resonance and asymmetric phonon emission
and absorption rate even around 50 K.
