Holographic storage of multiple coherence gratings in a Bose-Einstein condensate

We demonstrate superradiant conversion between a two-mode collective atomic state and a single-mode light field in an elongated cloud of Bose-condensed atoms. Two off-resonant write beams induce superradiant Raman scattering, producing two independent coherence gratings with a different wave vector in the cloud. By applying phase-matched read beams after a controllable delay, the gratings can be selectively converted into the light field also in a superradiant way. Due to the large cooperativity parameter and the small velocity width of the condensate, a high conversion efficiency of $> 70$ % and a long storage time of $> 120$ $\mu$s were achieved.Comment: 5 pages, 4 figure

Chaotic dynamics of cold atoms in far-off-resonant donut beam

We describe the classical two dimensinal nonlinear dynamics of cold atoms in far-off-resonant donut beams. We show that there chaotic dynamics exists for charge greater than unity, when the intensity of the beam is periodically modulated. The two dimensional distributions of atoms in $(x,y)$ plane for charge two are simulated. We show that the atoms will acumulate on several ring regions when the system enters to regime of global chaos.Comment: 8 pages, 8 figure

Phase transformation of mesoporous calcium carbonate by mechanical stirring

We report a simple strategy to synthesize vaterite/calcite mesoporous calcium carbonate through collisions and organization of colloidal particles accelerated by mechanical stirring. Mechanically stirring the precursor colloidal dispersion can control the calcium carbonate polymorphs

Scalable and template-free production of mesoporous calcium carbonate and its potential to formaldehyde adsorbent

Here we report a scalable and template-free production strategy 1 in the synthesis of a mesoporous calcium carbonate, which undergoes self-assembled nanostructure formation through a temperature-induced aggregation and polymorphic transformation of the colloids. The specific surface area and pore size distribution of resulting mesoporous calcium carbonate are clearly different depending on the aging temperature. The specific surface area and average pore size for aging temperature of 293 K are 207.3 ± 9.8 m2/g and 8.8±0.6 nm, respectively, and 65.1 ± 10.1 m2/g and 19.9±2.6 nm at 473 K. Additionally, we apply the mesoporous calcium carbonate powder to formaldehyde vapor adsorbent. We measure the adsorbed amount of gaseous formaldehyde and find that the vaterite-rich powder has larger adsorption per unit area than the calcite-rich one

The Transformation Process of Research Awareness as Understood through the Narratives of Students Formerly Enrolled in the Doctoral Program of the Graduate School of Education

　In this study, a qualitative analysis, Trajectory Equifinality Modeling (TEM), was used to highlight the transformation process of the research awareness of four former doctoral students. The doctoral programs to which the students formerly belonged train researchers and professional educators who are capable of research and practice. The authors describe the trajectory of the students advancing to their respective Equifinality Points through various experiences and possibilities despite fluxes in their research awareness. Citing the TEM diagrams drawn, the authors discuss: 1. The existence of change in the research environment and the reality of the adaptation process. 2. The existence of a period of exploration as a practicing researcher. 3. The meaning of the Obligatory Passage Points for students in doctoral programs in education. Closing the article, the authors examine future issues

New high-efficiency source of photon pairs for engineering quantum entanglement

We have constructed an efficient source of photon pairs using a waveguide-type nonlinear device and performed a two-photon interference experiment with an unbalanced Michelson interferometer. Parametric down-converted photons from the nonlinear device are detected by two detectors located at the output ports of the interferometer. Because the interferometer is constructed with two optical paths of different length, photons from the shorter path arrive at the detector earlier than those from the longer path. We find that the difference of arrival time and the time window of the coincidence counter are important parameters which determine the boundary between the classical and quantum regime. When the time window of the coincidence counter is smaller than the arrival time difference, fringes of high visibility (80$\pm$ 10%) were observed. This result is only explained by quantum theory and is clear evidence for quantum entanglement of the interferometer's optical paths.Comment: 4 pages, 4 figures, IQEC200