  We charge an individual donor with electrons stored in a quantum dot in its
proximity. A Silicon quantum device containing a single Arsenic donor and an
electrostatic quantum dot in parallel is realized in a nanometric field effect
transistor. The different coupling capacitances of the donor and the quantum
dot with the control and the back gates are exploited to generate a relative
rigid shift of their energy spectrum as a function of the back gate voltage,
causing the crossing of the energy levels. We observe the sequential tunneling
through the $D^{2-}$ and the $D^{3-}$ energy levels of the donor hybridized at
the oxide interface at 4.2 K. Their respective states form an honeycomb pattern
with the quantum dot states. It is therefore possible to control the exchange
coupling of an electron of the quantum dot with the electrons bound to the
donor, thus realizing a physical qubit for quantum information processing
applications.
