Bright single-photon sources in bottom-up tailored nanowires

The ability to achieve near-unity light extraction efficiency is necessary for a truly deterministic single photon source. The most promising method to reach such high efficiencies is based on embedding single photon emitters in tapered photonic waveguides defined by top-down etching techniques. However, light extraction efficiencies in current top-down approaches are limited by fabrication imperfections and etching induced defects. The efficiency is further tempered by randomly positioned off-axis quantum emitters. Here, we present perfectly positioned single quantum dots on the axis of a tailored nanowire waveguide using bottom-up growth. In comparison to quantum dots in nanowires without waveguide, we demonstrate a 24-fold enhancement in the single photon flux, corresponding to a light extraction efficiency of 42 %. Such high efficiencies in one-dimensional nanowires are promising to transfer quantum information over large distances between remote stationary qubits using flying qubits within the same nanowire p-n junction.Comment: 19 pages, 6 figure

Pion propagation in real time field theory at finite temperature

We describe how the thermal counterpart of a vacuum two-point function may be obtained in the real time formalism in a simple way by using directly the $2\times 2$ matrices that different elements acquire in this formalism. Using this procedure we calculate the analytic (single component) thermal amplitude for the pion pole term in the ensemble average of two axial-vector currents to two loops in chiral perturbation theory. The general expressions obtained for the effective mass and decay constants of the pion are evaluated in the chiral and the nonrelativistic limits. We also investigate the effect of massive states on these effective parameters.Comment: 17 pages TeX and 9 eps figure

Divergences in Real-Time Classical Field Theories at Non-Zero Temperature

The classical approximation provides a non-perturbative approach to time-dependent problems in finite temperature field theory. We study the divergences in hot classical field theory perturbatively. At one-loop, we show that the linear divergences are completely determined by the classical equivalent of the hard thermal loops in hot quantum field theories, and that logarithmic divergences are absent. To deal with higher-loop diagrams, we present a general argument that the superficial degree of divergence of classical vertex functions decreases by one with each additional loop: one-loop contributions are superficially linearly divergent, two-loop contributions are superficially logarithmically divergent, and three- and higher-loop contributions are superficially finite. We verify this for two-loop SU(N) self-energy diagrams in Feynman and Coulomb gauges. We argue that hot, classical scalar field theory may be completely renormalized by local (mass) counterterms, and discuss renormalization of SU(N) gauge theories.Comment: 31 pages with 7 eps figure

Does media use result in more active communicators? Differences between native Dutch and Turkish-Dutch patients in information-seeking behavior and participation during consultations with general practitioners

This study investigates differences between native Dutch and Turkish-Dutch patients with respect to media usage before and patient participation during medical consultations with general practitioners. In addition, the authors assessed the relation between patient participation and communication outcomes. The patients were recruited in the waiting rooms of general practitioners, and 191 patients (117 native Dutch, 74 Turkish-Dutch) completed pre- and postconsultation questionnaires. Of this sample, 120 patients (62.8%; 82 native Dutch, 38 Turkish-Dutch) agreed to have their consultations recorded to measure patient participation. Compared with Turkish-Dutch patients of similar educational levels, results showed that native Dutch patients used different media to search for information, participated to a greater extent during their consultations and were more responsive to their general practitioner. With respect to the Turkish-Dutch patients, media usage was related to increased patient participation, which was correlated with having fewer unfulfilled information needs; however, these relations were not found in the native Dutch patient sample. In conclusion, interventions that enhance participation among ethnic minority patients will better fulfill informational needs when such interventions stimulate information-seeking behavior in that group before a medical consultation