Electrical detection of coherent 31P spin quantum states

In recent years, a variety of solid-state qubits has been realized, including quantum dots, superconducting tunnel junctions and point defects. Owing to its potential compatibility with existing microelectronics, the proposal by Kane on the basis of phosphorus donors in silicon has been pursued intensively. A key issue of this concept is the readout of the 31P quantum state. Electrical measurements of magnetic resonance have been carried out on single spins, but the statistical nature of these experiments based on random-telegraph-noise measurements has impeded the readout of single spin states. Here, we demonstrate the measurement of the spin state of 31P donor electrons in silicon and the observation of Rabi flops by purely electric means, that is by coherent manipulation of spin-dependent charge-carrier recombination between the 31P donor and paramagnetic localized states at the Si/SiO2 interface. The electron spin information is shown to be coupled through the hyperfine interaction to the 31P nucleus, suggesting that recombination-based readout of nuclear spins is feasible.