  We propose and study an "intrinsic probing" approach, without introducing any
external detector, to mimic cavity QED effects in a qubit-nanomechanical
resonator system. This metallic nanomechanical resonator can act as an
intrinsic detector when a weak driving current passes through it. The
nanomechanical resonator acts as both the cavity and the detector. A cavity
QED-like effect is demonstrated by the correlation spectrum of the
electromotive force between the two ends of the nanomechanical resonator. Using
the quantum regression theorem and perturbation theory, we analytically
calculate the correlation spectrum. In the weak driving limit, we study the
effect on the vacuum Rabi splitting of both the strength of the driving as well
as the frequency-detuning between the charge qubit and the nanomechanical
resonator. Numerical calculations confirm the validity of our intrinsic probing
approach.
