Exciton-spin memory with a semiconductor quantum dot molecule
  We report on a single photon and spin storage device based on a semiconductor quantum dot molecule. Optically excited single electron-hole pairs are trapped within the molecule and their recombination rate is electrically controlled over three orders of magnitude. Single photons are stored up to 1 microsecond and read out on a sub-nanosecond timescale. Using resonant excitation, the circular polarisation of individual photons is transferred into the spin state of electron-hole pairs with a fidelity above 80%, which does not degrade for storage times up to the 12.5ns repetition period of the experiment. 
A. Boyer de la Giroday, N. Skold, R.M. Stevenson, I. Farrer, D.A.   Ritchie, A.J. Shields
quant-ph cond-mat.mes-hall