We propose and demonstrate the sequential initialization, optical control, and readout of a single spin trapped in a semiconductor quantum dot. Hole spin preparation is achieved through ionization of a resonantly excited electron-hole pair. Optical control is observed as a coherent Rabi rotation between the hole and charged-exciton states, which is conditional on the initial hole spin state. The spin-selective creation of the charged exciton provides a photocurrent readout of the hole spin state. DOI: 10.1103/PhysRevLett.100.197401 PACS numbers: 78.67.Hc, 42.50.Hz, 71.35.Pq The ability to sequentially initialize, control, and readout a single spin is an essential requirement of any spin based quantum information protocol [1]. This has not yet been achieved for promising schemes based on the optical control of semiconductor quantum dots [2]. These schemes seek to combine the picosecond optical gate speeds of excitons [3][4][5][6], with the potential for millisecond coherence times of quantum dot spins [7][8][9], by optically manipulating the spin via the charged exciton. This results in a system where the potential number of operations before coherence loss could be extremely high, in the range 10 4-9 , and in a system compatible with advanced semiconductor device technologies. A number of important milestones have recently been reached, but these focus on the continuous initialization of an electron [10,11] or hole spin [12], detection of a single quantum dot spin [13,14], or optical control of ensembles of 10 6-7 spins [15,16]. In this Letter, we demonstrate sequential triggered ondemand preparation, optical manipulation, and picosecond time-resolved detection of a single hole spin confined to a quantum dot, thus demonstrating an experimental framework for the fast optical manipulation of single spins. This is achieved using a single self-assembled InGaAs quantum dot embedded in a photodiode structure. The hole spin is prepared by ionizing an electron-hole pair created by resonant excitation. A second laser pulse then drives a coherent Rabi oscillation between the hole and positive trion states, which due to Pauli blocking is conditional on the initial hole spin state, key requirements for the optical control of a spin via the trion transition. Because of Pauli blockade, creation of the charged exciton provides a photocurrent readout of the hole spin state.First we will describe the principle of operation. The qubit is represented by the spin states of the heavy hole (J Figure 1 shows an idealized quantum dot, embedded in an n-i-Schottky diode structure. An electric field is applied, such that the electron tunneling rate is much faster than the hole tunneling rate. The experiments use a sequence of two circularly polarized, timeseparated laser pulses, with a time duration shorter than the electron tunneling time, labeled the ''preparation'' and ''control'' pulses. Figure 1 illustrates the steps (a)-(d) involved in the preparation and readout of the hole spin.Preparation.-(a) The circularly polarized prepar...

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GaAsSbN/GaAs strained-layer single quantum wells grown on a GaAs substrate by molecular-beam epitaxy with different N concentrations were studied using the photoluminescence ͑PL͒ technique in the temperature range from 9 to 296 K. A strong redshift in optical transition energies induced by a small increase in N concentration has been observed in the PL spectra. This effect can be explained by the interaction between a narrow resonant band formed by the N-localized states and the conduction band of the host semiconductor. Excitonic transitions in the quantum wells show a successive red/blue/redshift with increasing temperature in the 2-100 K range. The activation energies of nonradiative channels responsible for a strong thermal quenching are deduced from an Arrhenius plot of the integrated PL intensity.