This is an illustration of a photon gun. A quantum dot (the yellow symbol) emits one photon (red wave packet) at a time. The quantum dot is embedded in a photonic crystal structure, which is obtained by etching holes (black circles) in a semiconductor material. Due to the holes, the photons cannot be emitted in all directions, but only along the waveguide, which is formed by omitting a number of holes. Credit: Illustration: Søren Stobbe, NBI

Advanced photonic nanostructures are well on their way to revolutionising quantum technology for quantum networks based on light. Researchers from the Niels Bohr Institute have now developed the first building blocks needed to construct complex quantum photonic circuits for quantum networks...

Highly ordered sodium silicate particles (bottom right) with a regular array of spherical pores (bottom left) form on silicon surface. The one-step synthesis is directed by the atomic ordering of the substrate, which induces the formation of a soft template for sodium silicate growth. Sodium silicate, in turn, modifies the structure of the soft template during growth, encapsulating it within its structure (top). Credit: Image courtesy of Pacific Northwest National Laboratory

To create more efficient catalysts, sensing and separation membrane, and energy storage devices, scientists often start with particles containing tiny pore channels. Defects between the particles can hamper performance...

Backscattered electron images of urban cosmic spherules. Credit: M.J. Genge et al., Geology

More than 100 billion micrometeorites (MMs) fall to Earth each year. Until now, scientists believed that these particles could only be found in the cleanest environments, such as the Antarctic. In their new paper for Geology, M.J. Genge and colleagues show that, contrary to that expectation, micrometeorites can be recovered from city rooftops (eg, primarily in Norway) and that, unlike those from the Antarctic, they are the youngest collected to date.

This is not a new proposition. It has been a popular belief among amateur astronomers that such modern-day extraterrestrial dust can be collected on roofs in urban environments...

The PROCYON spacecraft and comet 67P/Churumov-Gerasiment (Conceptual Image). Credit: NAOJ/ESA/Go Miyazaki

In September 2015, a team of astronomers from the National Astronomical Observatory of Japan, University of Michigan, Kyoto Sangyo University, Rikkyo University and the University of Tokyo successfully observed the entire hydrogen coma of the comet 67P/Churyumov-Gerasimenko, using LAICA telescope onboard the PROCYON spacecraft. They also succeeded in obtaining the absolute rate of water discharge from the comet.

This comet was the target of ESA’s Rosetta mission in 2015. Because the Rosetta spacecraft was actually inside the cometary coma, it couldn’t observe the overall coma structure...