Entanglement of individual photon and atomic ensembles
  Here we present an experimentally feasible scheme to entangle flying qubit (individual photon with polarization modes) and stationary qubit (atomic ensembles with long-lived collective excitations). This entanglement integrate two different species can act as a critical element for the coherent transform of quantum information between flying and stationary qubits. The entanglement degree can be also adjusted expediently with linear optics. Furthermore, the present scheme can be modified to generate this entanglement in a way event-ready with the employment of a pair of entangled photons. Then successful preparation can be unambiguously heralded by coincident between two single-photon detectors. Its application for individal photons quantum memory is also analyzed. The physical requirements of all those preparation and applications processing are moderate, and well fit the present technique. 
Guo-Ping Guo and Guang-Can Guo