Experimental position-time entanglement with degenerate single photons

We report an experiment in which two-photon interference occurs between degenerate single photons that never meet. The two photons travel in opposite directions through our fibre-optic interferometer and interference occurs when the photons reach two different, spatially separated, 2-by-2 couplers at the same time. We show that this experiment is analogous to the conventional Franson-type entanglement experiment where the photons are entangled in position and time. We measure wavefunction overlaps for the two photons as high as 94 $\pm$ 3%.Comment: Updated to published version, new fig. 4., corrected typo

Surface acoustic wave-induced electroluminescence intensity oscillation in planar light-emitting devices

Electroluminescence emission from surface acoustic wave-driven light-emitting diodes (SAWLEDs) is studied by means of time-resolved techniques. We show that the intensity of the SAW-induced electroluminescence is modulated at the SAW frequency (~1 GHz), demonstrating electron injection into the p-type region synchronous with the SAW wavefronts.Comment: 4 pages, 3 figure

Children's reactions to inequality: Associations with empathy and parental teaching

The final publication is available at Elsevier via http://dx.doi.org/https://doi.org/10.1016/j.appdev.2020.101189. © 2020. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/While children generally prefer equal distributions of resources, we know little about the contextual and individual variability in these preferences. The present work examined experimental manipulations and associations between individual differences in empathy and parental teaching of “just world beliefs”, and children's perceptions of, and reactions to, unequal distributions. Children (aged 5–8, N = 96) watched videos of two puppets receiving unequal resources in varying contexts: distribution by one or multiple individuals, crossed with taking the perspective of the advantaged or disadvantaged puppet. Age was positively associated with perceived unfairness. Behavioural reactions to distributions were associated with individual and contextual factors: Greater cognitive empathy and lower teaching of just world beliefs were associated with increased rectification, and children with greater affective empathy favoured the disadvantaged puppet, but these relations only emerged in certain contexts. Findings provide guidance for interventions aimed at promoting morality, suggesting emphasis on behavioural responses to inequality and empathy-training.Funder 1,This work was supported by a Social Sciences and Humanities Research Council (SSHRC) Insight Grant awarded to E.N. and a SSHRC Insight Grant awarded to R.B

Magnetic-field-induced reduction of the exciton polarization splitting in InAs quantum dots

By the application of an in-plane magnetic field, we demonstrate control of the fine structure polarisation splitting of the exciton emission lines in individual InAs quantum dots. The selection of quantum dots with certain barrier composition and confinement energies is found to determine the magnetic field dependent increase or decrease of the separation of the bright exciton emission lines, and has enabled the splitting to be tuned to zero within the resolution of our experiments. Observed behaviour allows us to determine g-factors and exchange splittings for different types of dots.Comment: 12 pages, 3 figure

Broadband omnidirectional antireflection coating based on subwavelength surface Mie resonators

Reflection is a natural phenomenon that occurs when light passes the interface between materials with different refractive index. In many applications, such as solar cells or photodetectors, reflection is an unwanted loss process. Many ways to reduce reflection from a substrate have been investigated so far, including dielectric interference coatings, surface texturing, adiabatic index matching and scattering from plasmonic nanoparticles. Here we present an entirely new concept that suppresses the reflection of light from a silicon surface over a broad spectral range. A two-dimensional periodic array of subwavelength silicon nanocylinders designed to possess strongly substrate-coupled Mie resonances yields almost zero total reflectance over the entire spectral range from the ultraviolet to the near-infrared. This new antireflection concept relies on the strong forward scattering that occurs when a scattering structure is placed in close proximity to a high-index substrate with a high optical density of states

Cancellation of fine-structure splitting in quantum dots by a magnetic field

We demonstrate control of the fine-structure splitting of the exciton emission lines in single InAs quantum dots by the application of an in-plane magnetic field. The composition of the barrier material and the size and symmetry of the quantum dot are found to determine decrease or increase in the linear polarization splitting of the dominant exciton emission lines with increasing magnetic field. This enables the selection of dots for which the splitting can to be tuned to zero, within the resolution of our experiments. General differences in the g-factors and exchange splittings are found for different types of dot. (c) 2006 Elsevier B.V. All rights reserved