Efficient quantum memory using a weakly absorbing sample

A light-storage experiment with a total (storage and retrieval) efficiency $\eta=58 \pm 5$ is carried out by enclosing a sample, with a single pass absorption of 10%, in an impedance-matched cavity. The experiment is carried out using the Atomic Frequency Comb (AFC) technique in a praseodymium-doped crystal ($0.05$) and the cavity is created by reflection coating the crystal surfaces. The AFC technique has previously by far demonstrated the highest multi-mode capacity of all quantum memory concepts tested experimentally. We claim that the present work shows that it is realistic to create efficient, on-demand, long storage time AFC memories

Cavity enhanced storage - preparing for high efficiency quantum memories

Cavity assisted quantum memory storage has been proposed [PRA 82, 022310 (2010), PRA 82, 022311 (2010)] for creating efficient (close to unity) quantum memories using weakly absorbing materials. Using this approach we experimentally demonstrate a significant (about 20-fold) enhancement in quantum memory efficiency compared to the no cavity case. A strong dispersion originating from absorption engineering inside the cavity was observed, which directly affect the cavity line-width. A more than 3 orders of magnitude reduction of cavity mode spacing and cavity line-width from GHz to MHz was observed. We are not aware of any previous observation of several orders of magnitudes cavity mode spacing and cavity line-width reduction due to slow light effects.Comment: 13 pages, 5 figure

Spectral Engineering of Slow Light, Cavity Line Narrowing, and Pulse Compression

More than 4 orders of magnitude of cavity-linewidth narrowing in a rare-earth-ion-doped crystal cavity, emanating from strong intracavity dispersion caused by off-resonant interaction with dopant ions, is demonstrated. The dispersion profiles are engineered using optical pumping techniques creating significant semipermanent but reprogrammable changes of the rare-earth absorption profiles. Several cavity modes are shown within the spectral transmission window. Several possible applications of this phenomenon are discussed.Comment: arXiv admin note: substantial text overlap with arXiv:1304.445

Right-sided Diaphragmatic Eventration: A Case Report

Background: Diaphragmatic eventration is a rare congenital developmental defect of the muscular portion of diaphragm resulting diaphragmatic elevation. Eventration can be unilateral or bilateral, partial or complete. It is more common in males, and involves more often the left hemidiaphragm.Case Report: A 62-year-old man presented with complaints of chronic abdominal pain and dyspnea. In recent months, he suffered from an exertional dyspnea. With the radiological investigations, a diagnosis of eventration of right diaphragm was made and the diaphragmatic plication was done.Conclusions: Complete eventration of diaphragm invariably occurs on the left side; but partial eventration of diaphragm occurs virtually on the right side, and is diagnosed based on different radiologic findings. In this case, complete eventration of diaphragm was seen on the right side which is a rarity

Friction-stir welding of ultrafine grained austenitic 304L stainless steel produced by martensitic thermomechanical processing

An ultrafine grained 304L austenitic stainless steel was produced by martensitic thermomechanical processing and joined by applying Friction Stir Welding (FSW). The thermomechanical processing comprised a cold roll procedure up to 80% reduction followed by annealing. After FSW, different grain structures in different regions of the weld nugget were observed due to the asymmetry in the heat generation during the welding process. Grain growth was found to be the most predominant phenomena in the region just ahead of the rotating tool during the thermal cycle of FSW. A banded structure was observed in the advancing side of the weld nugget. TEM observations revealed that nanometric sigma phase precipitates were present both in the grain boundaries and inside the grains of this region. Shear textures were clearly identified in the weld center. The lack of rotated cube texture shows that the discontinuous dynamic recrystallization (DDRX) is not active in the final microstructure. Increasing the welding speed can reduce the final grain size of the weld nugget leading to higher hardness. Hardness is found to increase in the weld and this is not just a grain refinement effect, but also due to the presence of sub-boundaries and a high density of dislocations.postprin

Hyperfine characterization and coherence lifetime extension in Pr3+:La2(WO4)3

Rare-earth ions in dielectric crystals are interesting candidates for storing quantum states of photons. A limiting factor on the optical density and thus the conversion efficiency is the distortion introduced in the crystal by doping elements of one type into a crystal matrix of another type. Here, we investigate the system Pr3+:La2(WO4)3, where the similarity of the ionic radii of Pr and La minimizes distortions due to doping. We characterize the praseodymium hyperfine interaction of the ground state (3H4) and one excited state (1D2) and determine the spin Hamiltonian parameters by numerical analysis of Raman-heterodyne spectra, which were collected for a range of static external magnetic field strengths and orientations. On the basis of a crystal field analysis, we discuss the physical origin of the experimentally determined quadrupole and Zeeman tensor characteristics. We show the potential for quantum memory applications by measuring the spin coherence lifetime in a magnetic field that is chosen such that additional magnetic fields do not shift the transition frequency in first order. Experimental results demonstrate a spin coherence lifetime of 158 ms - almost three orders of magnitude longer than in zero field.Comment: 14 pages, 6 figure

Storage and recall of weak coherent optical pulses with an efficiency of 25%

We demonstrate experimentally a quantum memory scheme for the storage of weak coherent light pulses in an inhomogeneously broadened optical transition in a Pr^{3+}: YSO crystal at 2.1 K. Precise optical pumping using a frequency stable (about 1kHz linewidth) laser is employed to create a highly controllable Atomic Frequency Comb (AFC) structure. We report single photon storage and retrieval efficiencies of 25%, based on coherent photon echo type re-emission in the forward direction. The coherence property of the quantum memory is proved through interference between a super Gaussian pulse and the emitted echo. Backward retrieval of the photon echo emission has potential for increasing storage and recall efficiency.Comment: 5,