Statistics of Chaotic Resonances in an Optical Microcavity

Distributions of eigenmodes are widely concerned in both bounded and open systems. In the realm of chaos, counting resonances can characterize the underlying dynamics (regular vs. chaotic), and is often instrumental to identify classical-to-quantum correspondence. Here, we study, both theoretically and experimentally, the statistics of chaotic resonances in an optical microcavity with a mixed phase space of both regular and chaotic dynamics. Information on the number of chaotic modes is extracted by counting regular modes, which couple to the former via dynamical tunneling. The experimental data are in agreement with a known semiclassical prediction for the dependence of the number of chaotic resonances on the number of open channels, while they deviate significantly from a purely random-matrix-theory-based treatment, in general. We ascribe this result to the ballistic decay of the rays, which occurs within Ehrenfest time, and importantly, within the timescale of transient chaos. The present approach may provide a general tool for the statistical analysis of chaotic resonances in open systems.Comment: 5 pages, 5 figures, and a supplemental informatio

Demonstration of Deutsch's Algorithm on a Stable Linear-Optical Quantum Computer

We report an experimental demonstration of quantum Deutsch's algorithm by using linear-optical system. By employing photon's polarization and spatial modes, we implement all balanced and constant functions for quantum computer. The experimental system is very stable and the experimental data are excellent in accordance with the theoretical results.Comment: 7 pages, 4 figure

Complete placenta previa in the second trimester: clinical and sonographic factors associated with its resolution

Objectives: This study was carried out to evaluate outcomes of pregnancies with complete placenta previa diagnosed in mid-pregnancy, and evaluate whether a history of caesarean section and placenta location effect the resolution of placenta previa.  Material and methods: A prospective observational study was conducted on patients diagnosed with complete placenta previa by ultrasound examination between 20+0 weeks and 25+6 weeks of gestation. Patients were grouped in terms of placenta location (anteriorly or posteriorly located) and presence/absence of prior caesarean section. Maternal demographics, ultrasound findings and pregnancy outcomes were subsequently compared between these groups. Statistical analysis was performed by using SPSS version 16.0.  Results: 70 patients with the above characteristics were recruited in our study. Of the 70 patients, 21 (30%) had prior caesarean section, and 41 (58.6%) had an anteriorly located placenta. Patients with prior cesarean delivery delivered earlier (36.9 ± 2.2 weeks versus 38.0 ± 1.8 weeks, P = 0.039). Furthermore, 74.3% of the placenta previa resolved by delivery. Prior caesarean section (RR 2.941, 95% CI 0.938–9.216, P 0.024) and anterior placenta (RR 3.805, 95% CI 1.126–12.855, P 0.031) were related to greater risk of persistence of placenta previa to term.  Conclusions: Prior caesarean section and anteriorly located placenta are important factors that modify the risk that previa will complicate delivery. Our findings may be useful for patient counselling and future management of the condition

Causal estimation of COVID-19 and SARS on China’s stock market: evidence from a time series counterfactual prediction

This investigation infers the time evolution causal effect of COVID-19 and SARS on China’s stock market based on predicting the counterfactual market response using a diffusion-regression state-space model. The results show that SARS caused an average negative impact of 5.4% on stock prices. In comparison, COVID-19 had a negative impact of 5.3%. Furthermore, considering China’s growing worldwide influence, this study carefully reselects the covariates and finds that the negative impact of COVID-19 on stock prices has conservatively increased to 10%, far stronger than the impact of SARS. The results show that the quantitative estimation of the causal effect of emergencies such as COVID-19 must be based on reliable counterfactual inference; only relying on statistical correlation measures may lead to biased estimation. The analysis of the time evolution characteristics of the causal effect shows that the negative impact caused by COVID-19 began to weaken within three days, while the impact of SARS lasted longer. The results show that the Chinese government’s strict lockdown achieved the effect of stopping losses in time, and this finding helps to provide a positive demonstration for worldwide epidemic response strategies