Optical Spin Initialization and Non-Destructive Measurement in a Quantum   Dot Molecule
  The spin of an electron in a self-assembled InAs/GaAs quantum dot molecule is optically prepared and measured through the trion triplet states. A longitudinal magnetic field is used to tune two of the trion states into resonance, forming a superposition state through asymmetric spin exchange. As a result, spin-flip Raman transitions can be used for optical spin initialization, while separate trion states enable cycling transitions for non-destructive measurement. With two-laser transmission spectroscopy we demonstrate both operations simultaneously, something not previously accomplished in a single quantum dot. 
Danny Kim, Sophia E. Economou, Stefan C. Badescu, Michael Scheibner,   Allan S. Bracker, Mark Bashkansky, Thomas L. Reinecke...