Storing Quantum Information via Atomic Dark Resonances

Abstract: In this thesis, after a brief review of some concepts of Quantum Optics, we analyze a three-level atomic system in the conditions of electromagnetically induced transparency (EIT), and we investigate the propagation of a gaussian pulse along a cigar-shaped cloud of both cold and hot atoms in EIT regime. In particular, we show that it is possible to amplify a slow propagating pulse without population inversion. We also analyze the regime of anomalous light propagation showing that it is possible to observe superluminal energy propagation. In these conditions, it is possible to imprint reversibly ('write') the information carried by the photons onto the atoms, specifically as a coherent pattern of atomic spins, and later the information stored in the atomic spins can be transferred back ('read') to the light field, implementing in this way a quantum memory. Besides, we analyze the propagation of a quantum field in an EIT medium sustaining dark state polaritons (DSP) in a quasi-particle picture. Here, the decoherence effects in this quantum memory for photons, by analyzing the fidelity of the quantum state transfer, and the emergence of parastatistics in the quasi-particle picture in gain medium are discussed. Finally, we introduce a polarization quantum memory for photons by using a tripod atomic configuration in which two ideal EIT windows appear and the two DSPs, scattering each other, show a solitonic behavior.