  We present a theory describing the semiclassical dynamics of a
superconducting flux qubit inductively coupled to a nanomechanical oscillator.
Focusing on the influence of the qubit on the mechanical element, and on the
nonlinear phenomena displayed by this device, we show that it exhibits
retardation effects and self-excited oscillations. These can be harnessed for
the generation of non-classical states of the mechanical oscillator. In
addition, we find that this system shares several fundamental properties with
cavity optomechanical systems, and elucidate the analogy between these two
classes of devices.
