All Optical Implementation of Multi-Spin Entanglement in a Semiconductor   Quantum Well
  We use ultrafast optical pulses and coherent techniques to create spin entangled states of non-interacting electrons bound to donors (at least three) and at least two Mn2+ ions in a CdTe quantum well. Our method, relying on the exchange interaction between localized excitons and paramagnetic impurities, can in principle be applied to entangle a large number of spins. 
J. Bao, A. V. Bragas, J. K. Furdyna, and R. Merlin