  We analyze quantum charge pumping in an open ring with a dot embedded in one
of its arms. We show that cyclic driving of the dot levels by a \textit{single}
parameter leads to a pumped current when a static magnetic flux is
simultaneously applied to the ring. Based on the computation of the
Floquet-Green's functions, we show that for low driving frequencies $\omega_0$,
the interplay between the spatial interference through the ring plus
photon-assisted tunneling gives an average direct current (dc) which is
proportional to $\omega_0^{2}$. The direction of the pumped current can be
reversed by changing the applied magnetic field.
