Adiabatic Charge Control in a Single Donor Atom Transistor

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.