Quantum Information Processing With Cold Atoms

In the present thesis, we present our experimental study on the applications of cold atoms in quantum information processing.We achieved the quantum interface between cavity-enhanced narrow-band polarized entangled photons and the quantum memory composed of cold atom ensembles. With this interface we succeeded in mapping the quantum states of the entangled photons into and out of the quantum memory, and proved that the entanglement between the stored photons and flying photons still exist. Fur-thermore, we extended the quantum memory both in memory modes and memory performance, and we faithfully stored the biphoton entangled states into the quan-tum memory and read out with a total fidelity over98%.We also studied the possibility of realizing the many-body entanglement be-tween atoms in optical lattices. We first achieved the Bose-Einstein condensates of87Rb and squeezed the BEC into a two-dimensional system. We then loaded the2D quantum gas into optical lattices and observed the phase transition from Superfluid to Mott-insulator. Furthermore, we discussed the feasibility to realize the many-body entanglement in optical superlattices.The techniques we have developed in experiment will be very useful for the future research in long-distance quantum communication, scalable linear quantum computation, quantum simulation, topological quantum states, etc.