Controlled light-matter coupling for a single quantum dot embedded in a pillar microcavity using far-field optical lithography

Using far field optical lithography, a single quantum dot is positioned within a pillar microcavity with a 50 nm accuracy. The lithography is performed in-situ at 10 K while measuring the quantum dot emission. Deterministic spectral and spatial matching of the cavity-dot system is achieved in a single step process and evidenced by the observation of strong Purcell effect. Deterministic coupling of two quantum dots to the same optical mode is achieved, a milestone for quantum computing.Comment: Modified version: new title, additional experimental data in figure

Simulation Study on JLEIC High Energy Bunched Electron Cooling

In the JLab Electron Ion Collider (JLEIC) project the traditional electron cooling technique is used to reduce the ion beam emittance at the booster ring, and to compensate the intrabeam scattering effect and maintain the ion beam emittance during the collision at the collider ring. Different with other electron coolers using DC electron beam, the proposed electron cooler at the JLEIC ion collider ring uses high energy bunched electron beam, provided by an ERL. In this paper, we report some recent simulation study on how the electron cooling rate will be affected by the bunched electron beam properties, such as the correlation between the longitudinal position and momentum, the bunch size, and the Larmor emittance

Nonequilibrium Green's function theory for transport and gain properties of quantum cascade structures

The transport and gain properties of quantum cascade (QC) structures are investigated using a nonequilibrium Green's function (NGF) theory which includes quantum effects beyond a Boltzmann transport description. In the NGF theory, we include interface roughness, impurity, and electron-phonon scattering processes within a self-consistent Born approximation, and electron-electron scattering in a mean-field approximation. With this theory we obtain a description of the nonequilibrium stationary state of QC structures under an applied bias, and hence we determine transport properties, such as the current-voltage characteristic of these structures. We define two contributions to the current, one contribution driven by the scattering-free part of the Hamiltonian, and the other driven by the scattering Hamiltonian. We find that the dominant part of the current in these structures, in contrast to simple superlattice structures, is governed mainly by the scattering Hamiltonian. In addition, by considering the linear response of the stationary state of the structure to an applied optical field, we determine the linear susceptibility, and hence the gain or absorption spectra of the structure. A comparison of the spectra obtained from the more rigorous NGF theory with simpler models shows that the spectra tend to be offset to higher values in the simpler theories.Comment: 44 pages, 16 figures, appearing in Physical Review B Dec 200

Search for a new gauge boson in the A′A' Experiment (APEX)

We present a search at Jefferson Laboratory for new forces mediated by sub-GeV vector bosons with weak coupling $\alpha'$ to electrons. Such a particle $A'$ can be produced in electron-nucleus fixed-target scattering and then decay to an $e^+e^-$ pair, producing a narrow resonance in the QED trident spectrum. Using APEX test run data, we searched in the mass range 175--250 MeV, found no evidence for an $A'\to e^+e^-$ reaction, and set an upper limit of $\alpha'/\alpha \simeq 10^{-6}$. Our findings demonstrate that fixed-target searches can explore a new, wide, and important range of masses and couplings for sub-GeV forces.Comment: 5 pages, 5 figures, references adde

Health Links: Who Acts as a Source of Health Information in a Social Network?

Background: Members of a social network can influence the preventive health choices and cancer screening behaviors of other network members. Study Design: We conducted in-person interviews with 438 insured adults ages 40-70 in Massachusetts, Hawaii, and Georgia. We gathered information on social network communication regarding routine health topics and cancer screening. Participants reported whether family members and friends ask them for information or advice on health topics. Characteristics of each respondent’s social network were explored, including number of people with whom the participant has discussed colorectal cancer (CRC) screening. Participants were asked whether communication with social network members had ever led them to seek cancer screening. Principal Findings:80% of respondents in our group described themselves as a source of health information or advice for others in their social network (89% of women vs. 68% of men, p Conclusions: People who identified themselves as a source of health information within their social network were more likely to have discussed CRC screening with others and communicated with more people. Further study is necessary to understand the roles played by these individuals. As “health information ambassadors,” they may be effective targets for interventions that promote preventive screening

The first determination of Generalized Polarizabilities of the proton by a Virtual Compton Scattering experiment

Absolute differential cross sections for the reaction (e+p -> e+p+gamma) have been measured at a four-momentum transfer with virtuality Q^2=0.33 GeV^2 and polarization \epsilon = 0.62 in the range 33.6 to 111.5 MeV/c for the momentum of the outgoing photon in the photon-proton center of mass frame. The experiment has been performed with the high resolution spectrometers at the Mainz Microtron MAMI. From the photon angular distributions, two structure functions which are a linear combination of the generalized polarizabilities have been determined for the first time.Comment: 4 pages, 3 figure

Three design heuristics for enhancing the use of video to improve teaching practice

The use of video tools to support teacher learning has become increasingly widespread. While evidence points to the multiple affordances of video to enhance teacher learning, specific design principles that can guide the use of current video-based tools have not been well articulated. With the ultimate goal of developing a framework with shared design heuristics for the use of video to improve teaching practice, this paper describes the design strategies used by four research and development projects concerned with the use of video to support teacher learning in STEM subjects. Based on a review of the literature and inductive analyses of common design features across the four projects, three key design heuristics were identified. We describe the three heuristics including both a discussion of relevant literature and detailed examples of how the heuristics were implemented across the four projects. Altogether, the three design heuristics illustrate various ways to use video as a tool for teacher learning and yield insights that can inform the design of future video-based professional learning experiences