Spin–dependent recombination – an electronic readout mechanism for solid state quantum computers

It is shown that coherent spin motion of electron–hole pairs localized in band gap states of silicon can influence charge carrier recombination. Based on this effect, a readout concept for silicon based solid–state spin–quantum computers as proposed by Kane is suggested. The P quantum bit (qbit) is connected via hyperfine coupling to the spin of the localized donor electron. When a second localized and singly occupied electronic state with an energy level deep within the band gap or close to the valence edge is in proximity, a gate controlled exchange between the P nucleus and the two electronic states can be activated that leaves the donor–deep level pair either unchanged in a |T−〉-state or shifts it into a singlet state |S〉. Since the donor deep level transition is spin–dependent, the deep level becomes charged or not, depending on the nuclear spin orientation of the donor nucleus. Thus, the state of the qbit can be read with a sequence of light pulses and photo conductivity measurements. PACS numbers: 03.67.Lx, 72.25.-b, 72.20.Jv, 76.90.+d ∗electronic mail: [email protected]