Experimental Research On Quantum Memory With Cold Atoms

In the last decade, developing high-quality quantum memory has attracted lots of attentions in the field of quantum information due to its potential applications in var-ious areas, e.g. quantum information processing, quantum metrology, single-photon detection, and foundation of quantum mechanics. In this thesis, we present several experimental researches on quantum memory with cold atoms. Using EIT technique, we successfully achieved quantum interface between narrow-band photonic entangle-ment and cold atom quantum memory with high fidelity. The entanglement mapping into and out of the atom ensemble is well preserved. We also used ring cavity and Raman scattering method to generate and storage polarization entanglement with high retrieval efficiency, that up to75%. Combining techniques of the light-shift magnetic compensation and cavity-enhanced collective interaction, we then achieved an excel-lent quantum memory with both high retrieval efficiency and ultra-long storage time. The atoms are magic trapped by optical lattice, and the DLCZ process is enhanced by ring cavity. As a result, the lifetime of the storage is about0.38sec and initial internal retrieval efficiency is about80%. We believe that the techniques and achievements in this thesis will be very useful for further research in linear optical quantum compu-tation, long distance quantum communication, quantum key distribution, and also the test of foundation of quantum physics.