  We present experimental results showing phonon-mediated coupling between two
quantum dots embedded inside a photonic crystal microcavity. With only one of
the dots being spectrally close to the cavity, we observe both frequency
up-conversion and down-conversion of the pump light via a $\sim1.2$ THz phonon.
We demonstrate this process for both weak and strong regimes of dot-cavity
coupling, and provide a simple theoretical model explaining our observations.
