Fast optical preparation, control, and readout of a single quantum dot spin

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. © 2008 The American Physical Society

Nuclear spin switch in semiconductor quantum dots.

We show that by illuminating an InGaAs/GaAs self-assembled quantum dot with circularly polarized light, the nuclei of atoms constituting the dot can be driven into a bistable regime, in which either a thresholdlike enhancement or reduction of the local nuclear field by up to 3 T can be generated by varying the pumping intensity. The excitation power threshold for such a nuclear spin “switch” is found to depend on both the external magnetic and electric fields. The switch is shown to arise from the strong feedback of the nuclear spin polarization on the dynamics of the spin transfer from electrons to the nuclei of the dot

The Effects of Adenoviral Transfection of the Keratinocyte Growth Factor Gene on Epidermal Stem Cells: An \u3cem\u3eIn Vitro\u3c/em\u3e Study

Epidermal stem cells (ESCs) are characterized as slowcycling, multi-potent, and self-renewing cells that not only maintain somatic homeostasis but also participate in tissue regeneration and repair. To examine the feasibility of adenoviral vector-mediated keratinocyte growth factor (KGF) gene transfer into in vitro-expanded ESCs, ESCs were isolated from samples of human skin, cultured in vitro, and then transfected with recombinant adenovirus (Ad) carrying the human KGF gene (AdKGF) or green fluorescent protein gene (AdGFP). The effects of KGF gene transfer on cell proliferation, cell cycle arrest, cell surface antigen phenotype, and β-catenin expression were investigated. Compared to ESCs transfected with AdGFP, AdKGFtransfected ESCs grew well, maintained a high proliferative capacity in keratinocyte serum-free medium, and expressed high levels of β-catenin. AdKGF infection increased the number of ESCs in the G0/G1 phase and promoted ESCs entry into the G2/M phase, but had no effect on cell surface antigen phenotype (CD49f+/CD71−). The results suggest that KGF gene transfer can stimulate ESCs to grow and undergo cell division, which can be applied to enhance cutaneous wound healing