In recent years, a variety of solid-state qubits has been realized, including quantum dots [1,2], superconducting tunnel junctions [3,4] and point defects [5,6]. Due to its potential compatibility with existing microelectronics, the proposal by Kane [7,8] based on phosphorus donors in Si has also been pursued intensively [9,10,11]. A key issue of this concept is the readout of the 31 P quantum state. While electrical measurements of magnetic resonance have been performed on single spins [12,13], the statistical nature of these experiments based on random telegraph noise measurements has impeded the readout of single spin states. In this letter, we demonstrate the measurement of the spin state of 31 P donor electrons in silicon and the observation of Rabi flops by purely electric means, accomplished by coherent manipulation of spin-dependent charge carrier recombination between the 31 P donor and paramagnetic localized states at the Si/SiO2 interface via pulsed electrically detected magnetic resonance. The electron spin information is shown to be coupled through the hyperfine interaction with the 31 P nucleus, which demonstrates the feasibility of a recombinationbased readout of nuclear spins.Since the detection of single charges has become technically straight forward, it is widely believed [7,8,10,11,12] that the realization of spin-to-charge transfer is the key prerequisite for a successful implementation of single spin phosphorus ( 31 P) readout devices, capable of determining the actual spin state (spin up | ↑ or spin down | ↓ ). Different approaches to the electrical spin readout of 31 P-donor electron spins have been proposed based on spin-dependent transitions between neighboring 31 P atoms [7,8,10,11]. Since the states involved are energetically degenerate, these spin-to-charge transfer schemes are rather difficult to realize. Alternatively, spin-dependent transitions involving dissimilar paramagnetic states might be easier to detect as proposed by Boehme and Lips [14]. Spin-dependent charge carrier transport and recombination are known at least since 1966 [15], when Schmidt and Solomon already observed spin-dependent recombination involving 31 P donors in silicon. However, it was not demonstrated until 2003 [16] that the much more sensitive electrical detection of spins via resonant changes of recombination processes is also able to reflect coherent spin motion, which is necessary for a readout of the spin quantum state as opposed to a mere detection of the presence of spins. Figure 1(a) illustrates the readout scheme based on spin-dependent recombination demonstrated in this paper. In order to probe 31 P donor electron spins, spindependent excess charge carrier recombination through so-called P b0 centers is used. P b0 centers are trivalent Si atoms at the interface between crystalline silicon (c-Si) and silicon dioxide (SiO 2 ) that introduce localized, paramagnetic states in the Si band gap and dominate electron trapping and recombination at the interface [17,18]. If a neutral P b0 center is locate...

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We have investigated the role of doping and paramagnetic states on the electronic transport of networks assembled from freestanding Si nanocrystals (Si-NCs). Electrically detected magnetic resonance (EDMR) studies on Si-NCs films, which show a strong increase of conductivity with doping of individual Si-NCs, reveal that P donors and Si dangling bonds contribute to dark conductivity via spin-dependent hopping, whereas in photoconductivity, these states act as spin-dependent recombination centers of photogenerated electrons and holes. Comparison between EDMR and conventional electron paramagnetic resonance shows that different subsets of P-doped nanocrystals contribute to the different transport processes.