  We demonstrate a hybrid device architecture where the charge states in a
double quantum dot (DQD) formed in a Si/SiGe heterostructure are read out using
an on-chip superconducting microwave cavity. A quality factor Q = 5,400 is
achieved by selectively etching away regions of the quantum well and by
reducing photon losses through low-pass filtering of the gate bias lines.
Homodyne measurements of the cavity transmission reveal DQD charge stability
diagrams and a charge-cavity coupling rate g_c/2pi = 23 MHz. These measurements
indicate that electrons trapped in a Si DQD can be effectively coupled to
microwave photons, potentially enabling coherent electron-photon interactions
in silicon.
