Single-spin measurement using single-electron transistors to probe two-electron systems

We present a method for measuring single spins embedded in a solid by probi ng two-electron systems with a single-electron transistor (SET). Restrictio ns imposed by the Pauli principle on allowed two-electron states mean that the spin state of such systems has a profound impact on the orbital states (positions) of the electrons, a parameter which SET's are extremely well su ited to measure. We focus on a particular system capable of being fabricate d with current technology: a Te double donor in Si adjacent to a Si/SiO2, i nterface and lying directly beneath the SET island electrode, and we outlin e a measurement strategy capable of resolving single-electron and nuclear s pins in this system. We discuss the limitations of the measurement imposed by spin scattering arising from fluctuations emanating from the SET and fro m lattice phonons. We conclude that measurement of single spins, a necessar y requirement for several proposed quantum computer architectures, is feasi ble in Si using this strategy.