Negative Polarization through Photon to Electron Spin Polarization   Transfer in GaAs Quantum Wells
  We demonstrate negative polarization created by light-hole exciton excitation in g-factor engineered GaAs quantum wells measured by time-resolved Kerr rotation and polarization-resolved photoluminescence. This negative polarization is a result of polarization transfer from a photon to an electron spin mediated by a light hole. This demonstration is an important step towards achieving quantum media conversion from a photonic qubit to an electron spin qubit required for building a quantum repeater. 
H. Kosaka, Y. Rikitake, H. Imamura, Y. Mitsumori and K. Edamatsu