Generation of heralded Dicke state

We study experimentally the efficient creation of heralded Dicke states in an atomic ensemble trapped in a high finesse optical cavity. Weak resonant light in free-space mode transverse to the cavity is efficiently absorbed by the optically dense sample. Subsequent stimulated Raman scattering into the cavity mode dominates over free space scattering because of the high single atom cooperativity of the cavity. This result paves the way towards a high efficiency heralded quantum memory which will be practically useful for storing the polarization state of a single photon.