Quasiparticle relaxation in optically excited high-Q superconducting resonators

The quasiparticle relaxation time in superconducting films has been measured as a function of temperature using the response of the complex conductivity to photon flux. For tantalum and aluminium, chosen for their difference in electron-phonon coupling strength, we find that at high temperatures the relaxation time increases with decreasing temperature, as expected for electron-phonon interaction. At low temperatures we find in both superconducting materials a saturation of the relaxation time, suggesting the presence of a second relaxation channel not due to electron-phonon interaction.Comment: 4 pages, 3 figure

Enhancement of quasiparticle recombination in Ta and Al superconductors by implantation of magnetic and nonmagnetic atoms

The quasiparticle recombination time in superconducting films, consisting of the standard electron-phonon interaction and a yet to be identified low temperature process, is studied for different densities of magnetic and nonmagnetic atoms. For both Ta and Al, implanted with Mn, Ta and Al, we observe an increase of the recombination rate. We conclude that the enhancement of recombination is not due to the magnetic moment, but arises from an enhancement of disorder.Comment: 4 pages, 4 figure

A systematic review of practices to promote vegetable acceptance in the first three years of life.

Background: Although most children do not meet vegetable intake recommendations no clear universal guidelines exist on the best method of introducing and promoting vegetables in infants. Objective: To identify strategies to promote vegetable acceptance in children from the start of complementary feeding until 3 years of age. Design: A comprehensive search strategy was performed using the databases Scopus and Pubmed. Articles published before March 2018 measuring vegetable intake and/or liking were included. Results: 46 papers, 25 experimental (intervention) studies, and 21 observational studies were included. Intervention studies revealed that repeated exposure increased acceptance of the target vegetable, whereas exposure to variety was found to be particularly effective in increasing acceptance of a new vegetable. Starting complementary feeding with vegetables increased vegetable acceptance, whereas starting with fruits did not. Visual exposure to an unfamiliar vegetable increased the acceptance of that vegetable even without consuming it, while visual exposure to a familiar vegetable did not. A stepwise introduction of vegetables resulted in better initial acceptance of vegetables than introducing vegetables directly. Observational studies showed that vegetable consumption was associated with frequency of exposure, exposure to variety, and modelling. A majority of studies found a positive association between breastfeeding and vegetable acceptance, but only two out of seven studies found an association between age of vegetable introduction and their acceptance. Conclusions: Based on the papers reviewed, we conclude that introducing vegetables at the beginning of complementary feeding, giving a different type of vegetable every day and ensuring repeated exposure to the same vegetable following an interval of a few days are the most promising strategies to promote vegetable intake in children starting complementary feeding until they are 3 years of age

Planar Superconducting Resonators with Internal Quality Factors above One Million

We describe the fabrication and measurement of microwave coplanar waveguide resonators with internal quality factors above 10 million at high microwave powers and over 1 million at low powers, with the best low power results approaching 2 million, corresponding to ~1 photon in the resonator. These quality factors are achieved by controllably producing very smooth and clean interfaces between the resonators' aluminum metallization and the underlying single crystal sapphire substrate. Additionally, we describe a method for analyzing the resonator microwave response, with which we can directly determine the internal quality factor and frequency of a resonator embedded in an imperfect measurement circuit.Comment: 4 pages, 3 figures, 1 tabl

Excitation of superconducting qubits from hot non-equilibrium quasiparticles

Superconducting qubits probe environmental defects such as non-equilibrium quasiparticles, an important source of decoherence. We show that "hot" non-equilibrium quasiparticles, with energies above the superconducting gap, affect qubits differently from quasiparticles at the gap, implying qubits can probe the dynamic quasiparticle energy distribution. For hot quasiparticles, we predict a non-neligable increase in the qubit excited state probability P_e. By injecting hot quasiparticles into a qubit, we experimentally measure an increase of P_e in semi-quantitative agreement with the model and rule out the typically assumed thermal distribution.Comment: Main paper: 5 pages, 5 figures. Supplement: 1 page, 1 figure, 1 table. Updated to user-prepared accepted version. Key changes: Supplement added, Introduction rewritten, Figs.2,3,5 revised, Fig.4 adde