photon using the actual atomic levels of $^{87}$Rb.

Storage of a QD-generated Photon in $^{87}$R {#sec:QD}
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Because of the long hyperfine ground-state coherence time and the ability to create cold, dense gases, $^{87}$Rb has proven to be a natural choice for implementation of quantum memory schemes. Indeed, both the 5$^2$P$_{1/2}$ and 5$^2$P$_{3/2}$ excited state manifolds corresponding to the $D_1$ and $D_2$ optical transitions have been used for quantum memory applications. Before assigning $^{87}$Rb hyperfine states ${\ensuremath{|F,m_F\rangle}}$ to the various states of the four level model, the problem of frequency matching of a QD transition to the $D_2$/$D_1$ transitions at 780/795 nm must be addressed. The most commonly studied self-assembled QDs are composed of In$_x$Ga$_{1-x}$As islands embedded in a GaAs matrix, which are made to emit light in the 900-1000 nm band. In such QDs, the so-called “wetting layer" (a thin quantum well) defines a barrier near 850 nm, below which no confined states exist in the dot. Therefore, the photons produced by these QDs cannot be stored in $^{87}$Rb, but Cs transitions (852/895 nm) are close to within reach and $^{171}$Yb$^+$ (935 nm) has a transition compatible with QDs [@ref:Waks_PRA09]. Nonetheless, efficient quantum frequency conversion techniques have been demonstrated 