Subnatural-Linewidth Polarization-Entangled Photon Pairs with Controllable Temporal Length

We demonstrate an efficient experimental scheme for producing polarization-entangled photon pairs from spontaneous four-wave mixing (SFWM) in a laser-cooled $^{85}$Rb atomic ensemble, with a bandwidth (as low as 0.8 MHz) much narrower than the rubidium atomic natural linewidth. By stabilizing the relative phase between the two SFWM paths in a Mach-Zehnder interferometer configuration, we are able to produce all four Bell states. These subnatural-linewidth photon pairs with polarization entanglement are ideal quantum information carriers for connecting remote atomic quantum nodes via efficient light-matter interaction in a photon-atom quantum network.Comment: Title changed, published version, 5 pages + 3 pages Supplemental Materia

A kilonova associated with GRB 070809

For on-axis typical short gamma-ray bursts (sGRBs), the forward shock emission is usually so bright that renders the identification of kilonovae (also known as macronovae) in the early afterglow ($t<0.5$ d) phase rather challenging. This is why previously no thermal-like kilonova component has been identified at such early time except in the off-axis dim GRB 170817A associated with GW170817. Here we report the identification of an unusual optical radiation component in GRB 070809 at $t\sim 0.47$ d, thanks plausibly to the very-weak/subdominant forward shock emission. The optical emission with a very red spectrum is well in excess of the extrapolation of the X-ray emission that is distinguished by an unusually hard spectrum, which is at odds with the forward shock afterglow prediction but can be naturally interpreted as a kilonova. Our finding supports the speculation that kilonovae are ubiquitous , and demonstrates the possibility of revealing the neutron star merger origin with the early afterglow data of some typical sGRBs that take place well beyond the sensitive radius of the advanced gravitational wave detectors and hence the opportunity of organizing dedicated follow-up observations for events of interest.Comment: 20 pages, 5 figures, published in Nature Astronom

BUILDING A FACEBOOK EMBEDDED PICTURE BOOK DESIGN LEARNING PLATFORM AND UNDERSTANDING ITS USE INTENTIONS

Electronic reading is a process of digitalizing not only the content and reading devices but also the publication and distribution of books. With the development of e-books, more attention has been paid to use of e-books in education. Through online communities and innovative learning models, digital content providers can offer plenty of resources to help learners at all levels and promote the effectiveness of their self-regulated learning. The objective of this study is to build a cloud-based learning platform that integrates designs of electronic picture books and the social functions of Facebook. Students of multimedia design can upload their works to this platform and learn from each other through idea sharing and discussion. This platform is expected to help students create works with better quality and more creativity. Besides, this study also investigates the learning behavior and use intentions of students on this platform based on “Social Interaction Theory” and “Uses and Gratifications Theory”. This study attempts to capture students’ needs and how they are related to their learning outcomes. Results of this study contribute to the development of cloud-based learning and can be a reference for design of learning materials and improvement of teaching models

Multiconsensus of Second-Order Multiagent Systems with Input Delays

The multiconsensus problem of double-integrator dynamic multiagent systems has been investigated. Firstly, the dynamic multiconsensus, the static multiconsensus, and the periodic multiconsensus are considered as three cases of multiconsensus, respectively, in which the final multiconsensus convergence states are established by using matrix analysis. Secondly, as for the multiagent system with input delays, the maximal allowable upper bound of the delays is obtained by employing Hopf bifurcation of delayed networks theory. Finally, simulation results are presented to verify the theoretical analysis