GHz Rabi flopping to Rydberg states in hot atomic vapor cells

We report on the observation of Rabi oscillations to a Rydberg state on a timescale below one nanosecond in thermal rubidium vapor. We use a bandwidth-limited pulsed excitation and observe up to 6 full Rabi cycles within a pulse duration of ~ 4 ns. We find good agreement between the experiment and numerical simulations based on a surprisingly simple model. This result shows that fully coherent dynamics with Rydberg states can be achieved even in thermal atomic vapor thus suggesting small vapor cells as a platform for room temperature quantum devices. Furthermore the result implies that previous coherent dynamics in single atom Rydberg gates can be accelerated by three orders of magnitude.Comment: 4 pages, 3 figure

Ultracold chemical reactions of a single Rydberg atom in a dense gas

Within a dense environment ($\rho \approx 10^{14}\,$atoms/cm$^3$) at ultracold temperatures ($T < 1\,\mu{}\text{K}$), a single atom excited to a Rydberg state acts as a reaction center for surrounding neutral atoms. At these temperatures almost all neutral atoms within the Rydberg orbit are bound to the Rydberg core and interact with the Rydberg atom. We have studied the reaction rate and products for $nS$ $^{87}$Rb Rydberg states and we mainly observe a state change of the Rydberg electron to a high orbital angular momentum $l$, with the released energy being converted into kinetic energy of the Rydberg atom. Unexpectedly, the measurements show a threshold behavior at $n\approx 100$ for the inelastic collision time leading to increased lifetimes of the Rydberg state independent of the densities investigated. Even at very high densities ($\rho\approx4.8\times 10^{14}\,\text{cm}^{-3}$), the lifetime of a Rydberg atom exceeds $10\,\mu\text{s}$ at $n > 140$ compared to $1\,\mu\text{s}$ at $n=90$. In addition, a second observed reaction mechanism, namely Rb$_2^+$ molecule formation, was studied. Both reaction products are equally probable for $n=40$ but the fraction of Rb$_2^+$ created drops to below 10$\,$% for $n\ge90$.Comment: 13 pages, 13 figure

Reading, metacognition, and motivation: A follow-up study of German students in Grades 7 and 8

This follow-up study to van Kraayenoord and Schneider (1999) examined the performance in reading, metacognition and motivation related to reading of students in Grades 7 and 8. Results showed significant correlations between all of the variables. A multivariate analysis of variance showed that good and poor readers differed in reading self-concept and metacognitive measures related to reading and memory. A stepwise regression analysis suggested that the metacognitive variables were the best predictors of reading. Furthermore, a comparison of the results of the previous study with those of the current investigation revealed that the findings were stable over time. Since the period between the two studies is the time during which students make important decisions related to enrolment in one of three distinct school-types in Germany, we examined the results of various groups of students: those in Gymnasium (high educational track), Realschule (middle educational track), and Hauptschule (low educational track). Students in the Gymnasium scored significantly better than students in the other two groups on almost all variables related to reading. A re-analysis of the data from our first investigation found that the results of the Gymnasium students in the second study could be predicted from their results obtained during elementary school

Pathways to school achievement in very preterm and full term children

Individual differences in academic success were investigated in a geographically defined whole-population sample of very preterm children with a gestational age of less than 32 weeks or a birth weight of less than 1500 gm. The sample consisted of 264 very preterm children (75.6% of German-speaking survivors) and 264 controls matched for gender, socioeconomic status, marital status and age of mother, who were studied from birth. The present analyses focused on the impact of cognitive skills assessed at ages 6 and 8 on academic success at the age 13. IQ scores, prereading skills, reading, spelling, and math performance assessed during the last kindergarten year and again at the end of Grade 2 were used as predictors of academic success in early adolescence. Differences between very preterm children and controls in cognitive abilities already observed in earlier assessments remained stable over time, with controls on average performing more than half a standard deviation above the level of preterm children. Preterm children also performed poorer on the literacy measures and indicators of math performance. Multivariate and causal modeling revealed different prediction patterns for the two groups. Whereas IQ was particularly important for the prediction of academic success in the pre-term sample, general IQ was less relevant for the prediction of academic success in the control group. When subgroups of at-risk children were formed according to birth weight categories, we found that school problems were most pronounced for children with extremely low birth weight (1000 gm and less). (Contains 4 figures and 4 tables.