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Dark matter, the mysterious substance that constitutes most of the material universe, remains as elusive as ever. Although experiments on the ground and in space have yet to find a trace of dark matter, the results are helping scientists rule out some of the many theoretical possibilities. Three studies published earlier this year, using six or more years of data from NASA’s Fermi Gamma-ray Space Telescope, have broadened the mission’s dark matter hunt using some novel approaches.

“We’ve looked for the usual suspects in the usual places and found no solid signals, so we’ve started searching in some creative new ways,” said Julie McEnery, Fermi project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “With these results, Fermi has excluded more candidates, has shown that dark matter can contribute to only a small part of the gamma-ray background beyond our galaxy, the Milky Way, and has produced strong limits for dark matter particles in the second-largest galaxy orbiting it.”

Dark matter neither emits nor absorbs light, primarily interacts with the rest of the universe through gravity, yet accounts for about 80 percent of the matter in the universe. Astronomers see its effects throughout the cosmos—in the rotation of galaxies, in the distortion of light passing through galaxy clusters, and in simulations of the early universe, which require the presence of dark matter to form galaxies at all.

As the Large Hadron Collider’s first sign of a superparticle melts away, physicists must contemplate their nightmare scenario, says Gavin Hesketh

By Gavin Hesketh

Particle physics finds itself in testing times. This branch of science aims to describe the universe by pulling it apart into its most fundamental building blocks, or particles, and putting them back together in a way that explains how everything works.

Continue reading “LHC-style supercolliders are entering a make or break phase” »

Well, what about all the other stars that do *not* show this behavior?

Dmitry Fedyanin from the Moscow Institute of Physics and Technology and Mario Agio from the University of Siegen and LENS have predicted that artificial defects in the crystal lattice of diamond can be turned into ultrabright and extremely efficient electrically driven quantum emitters. Their work, published in New Journal of Physics, demonstrates the potential for a number of technological breakthroughs, including the development of quantum computers and secure communication lines that operate at room temperature.

The research conducted by Dmitry Fedyanin and Mario Agio is focused on the development of electrically driven single-photon sources—devices that emit single photons when an electrical current is applied. In other words, using such devices, one can generate a photon “on demand” by simply applying a small voltage across the devices. The probability of an output of zero photons is vanishingly low and generation of two or more photons simultaneously is fundamentally impossible.

Until recently, it was thought that quantum dots (nanoscale semiconductor particles) are the most promising candidates for true single-photon sources. However, they operate only at very low temperatures, which is their main drawback – mass application would not be possible if a device has to be cooled with liquid nitrogen or even colder liquid helium, or using refrigeration units, which are even more expensive and power-hungry. At the same time, certain point defects in the crystal lattice of diamond, which occur when foreign atoms (such as silicon or nitrogen) enter the diamond accidentally or through targeted implantation, can efficiently emit single photons at room temperature. However, this has only been achieved by optical excitation of these defects using external high-power lasers. This method is ideal for research in scientific laboratories, but it is very inefficient in practical devices.

Continue reading “Diamond-based light sources will lay a foundation for quantum communications of the future” »

IBM scientists have developed a new lab-on-a-chip technology that can, for the first time, separate biological particles at the nanoscale and could help enable physicians to detect diseases such as cancer before symptoms appear.

As reported today in the journal Nature Nanotechnology*, the IBM team’s results show size-based separation of bioparticles down to 20 nanometers (nm) in diameter, a scale that gives access to important particles such as DNA, viruses and exosomes. Once separated, these particles can be analyzed by physicians to potentially reveal signs of disease even before patients experience any physical symptoms and when the outcome from treatment is most positive. Until now, the smallest bioparticle that could be separated by size with on-chip technologies was about 50 times or larger, for example, separation of circulating tumor cells from other biological components.

IBM is collaborating with a team from the Icahn School of Medicine at Mount Sinai to continue development of this lab-on-a-chip technology and plans to test it on prostate cancer, the most common cancer in men in the U.S.

Continue reading “IBM lab on a chip can sort 20 nanometer nanoparticles such as DNA, viruses and exos” »

Hopes for the imminent discovery of a particle that might fundamentally change our understanding of the Universe have been put on hold.

Results from the Large Hadron Collider show that a “bump” in the machine’s data, previously rumoured to represent a new particle, has gone away.

The discovery of new particles, which could trigger a paradigm shift in physics, may still be years away.

A novel strategy is used to synthesize porous gold-silver alloy nanospheres encased in ultrathin silica shells that can act as highly sensitive single-particle probes.

Gold (Au) and silver (Ag) nanoparticles are typical plasmonic nanoparticles that exhibit an intense electromagnetic field in their proximity when they are irradiated by incident light. Within these fields—known as ‘hotspots’—the Raman scattering of molecules can be magnified by many orders of magnitude (depending on the intensity of the local electric field). In this so-called surface-enhanced Raman scattering (SERS) phenomenon,¹ the Raman scattering signals contain information relating to the bond vibrations and thus provide ‘signatures’ of the molecules (which enables their spectroscopic detection). In the pursuit of high-sensitivity SERS analyses, it is therefore highly desirable to specifically construct hotspots.

Continue reading “Porous plasmonic nanoparticles for surface-enhanced Raman scattering applications” »

All material things appear to be made of elementary particles that are held together by fundamental forces. But what are their exact properties? How do they affect how our universe looks and changes? And are there particles and forces that we don’t know of yet?

Questions with cosmic implications like these drive many of the scientific efforts at the Department of Energy’s SLAC National Accelerator Laboratory. Three distinguished particle physicists have joined the lab over the past months to pursue research on two particularly mysterious forms of matter: neutrinos and dark matter.

Neutrinos, which are abundantly produced in nuclear reactions, are among the most common types of particles in the universe. Although they were discovered 60 years ago, their basic properties puzzle scientists to this date.

Continue reading “Elusive neutrinos and hypothetical ‘dark sector’ particles could hold answers to cosmic mysteries” »

Quantum computers promise speedy solutions to some difficult problems, but building large-scale, general-purpose quantum devices is a problem fraught with technical challenges.

To date, many research groups have created small but functional quantum computers. By combining a handful of atoms, electrons or superconducting junctions, researchers now regularly demonstrate quantum effects and run simple quantum algorithms —small programs dedicated to solving particular problems.

But these laboratory devices are often hard-wired to run one program or limited to fixed patterns of interactions between the quantum constituents. Making a quantum computer that can run arbitrary algorithms requires the right kind of physical system and a suite of programming tools. Atomic ions, confined by fields from nearby electrodes, are among the most promising platforms for meeting these needs.

Continue reading “Programmable ions set the stage for general-purpose quantum computers” »