Lifeboat Foundation

The High-Luminosity upgrade of the Large Hadron Collider (HL-LHC) is scheduled to begin colliding protons in 2026. This major improvement to CERN’s flagship accelerator will increase the total number of collisions in the ATLAS experiment by a factor of 10. To cope with this increase, ATLAS is preparing a complex series of upgrades including the installation of new detectors using state-of-the-art technology, the replacement of aging electronics, and the upgrade of its trigger and data acquisition system.

What discovery opportunities will be in reach for ATLAS with the HL-LHC upgrade? How precisely will physicists be able to measure properties of the Higgs boson? How deeply will they be able to probe Standard Model processes for signs of new physics? The ATLAS Collaboration has carried out and released dozens of studies to answer these questions—the results of which have been valuable input to discussions held this week at the Symposium on the European Strategy for Particle Physics, in Granada, Spain.

“Studying the discovery potential of the HL-LHC was a fascinating task associated with the ATLAS upgrades,” says Simone Pagan Griso, ATLAS Upgrade Physics Group co-convener. “The results are informative not only to the ATLAS Collaboration but to the entire global particle-physics community, as they reappraise the opportunities and challenges that lie ahead of us.” Indeed, these studies set important benchmarks for forthcoming generations of particle physics experiments.

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Semiconductors, which are the basic building blocks of transistors, microprocessors, lasers, and LEDs, have driven advances in computing, memory, communications, and lighting technologies since the mid-20th century. Recently discovered two-dimensional materials, which feature many superlative properties, have the potential to advance these technologies, but creating 2-D devices with both good electrical contacts and stable performance has proved challenging.

Researchers at Columbia Engineering report that they have demonstrated a nearly ideal transistor made from a two-dimensional (2-D) material stack—with only a two-atom-thick semiconducting layer—by developing a completely clean and damage-free fabrication process. Their method shows vastly improved performance compared to 2-D semiconductors fabricated with a conventional process, and could provide a scalable platform for creating ultra-clean devices in the future. The study was published today in Nature Electronics.

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Protons are complicated. The subatomic particles are themselves composed of smaller particles called quarks and gluons. Now, data from the Large Hadron Collider hint that protons’ constituents don’t behave independently. Instead, they are tethered by quantum links known as entanglement, three physicists report in a paper published April 26 at arXiv.org.

Quantum entanglement has previously been probed on scales much larger than a proton. In experiments, entangled particles seem to instantaneously influence one another, sometimes even when separated by distances as large as thousands of kilometers (SN: 8/5/17, p. 14). Although scientists suspected that entanglement occurs within a proton, signs of that phenomenon hadn’t been experimentally demonstrated inside the particle, which is about a trillionth of a millimeter across.

“The idea is, this is a quantum mechanical particle which, if you look inside it, … it’s itself entangled,” says theoretical physicist Piet Mulders of Vrije Universiteit Amsterdam, who was not involved with the research.

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Physicists at the National Institute of Standards and Technology (NIST) and partners have demonstrated an experimental, next-generation atomic clock—ticking at high “optical” frequencies—that is much smaller than usual, made of just three small chips plus supporting electronics and optics.

Described in Optica, the chip-scale clock is based on the vibrations, or “ticks,” of rubidium atoms confined in a tiny glass container, called a vapor cell, on a chip. Two frequency combs on chips act like gears to link the atoms’ high-frequency optical ticks to a lower, widely used microwave frequency that can be used in applications.

The chip-based heart of the new clock requires very little power (just 275 milliwatts) and, with additional technology advances, could potentially be made small enough to be handheld. Chip-scale optical clocks like this could eventually replace traditional oscillators in applications such as navigation systems and telecommunications networks and serve as backup clocks on satellites.

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The ultimate degree of control for engineering would be the ability to create and manipulate materials at the most basic level, fabricating devices atom by atom with precise control.

Now, scientists at MIT, the University of Vienna, and several other institutions have taken a step in that direction, developing a method that can reposition atoms with a highly focused electron beam and control their exact location and bonding orientation. The finding could ultimately lead to new ways of making quantum computing devices or sensors, and usher in a new age of “atomic engineering,” they say.

The advance is described today in the journal Science Advances, in a paper by MIT professor of nuclear science and engineering Ju Li, graduate student Cong Su, Professor Toma Susi of the University of Vienna, and 13 others at MIT, the University of Vienna, Oak Ridge National Laboratory, and in China, Ecuador, and Denmark.

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Machine learning (ML), a form of artificial intelligence that recognizes faces, understands language and navigates self-driving cars, can help bring to Earth the clean fusion energy that lights the sun and stars. Researchers at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) are using ML to create a model for rapid control of plasma—the state of matter composed of free electrons and atomic nuclei, or ions—that fuels fusion reactions.

The sun and most stars are giant balls of plasma that undergo constant fusion reactions. Here on Earth, scientists must heat and control the plasma to cause the particles to fuse and release their energy. PPPL research shows that ML can facilitate such control.

In materials science, achromatic optical components can be designed with high transparency and low dispersion. Materials scientists have shown that although metals are highly opaque, densely packed arrays of metallic nanoparticles with more than 75 percent metal by volume can become more transparent to infrared radiation than dielectrics such as germanium. Such arrays can form effective dielectrics that are virtually dispersion-free across ultra-broadband ranges of wavelengths to engineer a variety of next-generation metamaterial-based optical devices.

Scientists can tune the local refractive indices of such materials by altering the size, shape and spacing of nanoparticles to design gradient-index lenses that guide and focus light on the microscale. The electric field can be strongly concentrated in the gaps between metallic nanoparticles for the simultaneous focusing and ‘squeezing’ of the dielectric field to produce strong, doubly enhanced hotspots. Scientists can use these hotspots to boost measurements made using infrared spectroscopy and other non-linear processes across a broad frequency range.

In a recent study now published in Nature Communications, Samuel J. Palmer and an interdisciplinary research team in the departments of Physics, Mathematics and Nanotechnology in the U.K., Spain and Germany, showed that artificial dielectrics can remain highly transparent to infrared radiation and observed this outcome even when the particles were nanoscopic. They demonstrated the electric field penetrates the particles (rendering them imperfect for conduction) for strong interactions to occur between them in a tightly packed arrangement. The results will allow materials scientists to design optical components that are achromatic for applications in the mid-to-infrared wavelength region.

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A team of researchers from the University of California and Fudan University has developed a way to use a single molecule magnet as a scanning magnetometer. In their paper published in the journal Science, the group outlines their research which involved demonstrating their sensor scanning the spin and magnetic properties of a molecule embedded in another material.

As scientists continue their quest to squeeze ever more data onto increasingly smaller storage devices, they are exploring the possibility of using the magnetic state of a single molecule or even an atom—likely the smallest possible memory element type. In this new effort, the researchers have demonstrated that it is possible to use a single molecule affixed to a sensor to read the properties of a single molecule in another material.

To create their sensor and storage medium, the researchers first absorbed magnetic molecules of Ni(cyclopentadienyl)₂ onto a plate coated with silver. Then, they pulled a nickelocene molecule from the silver surface and applied it to the tip of a scanning tunneling microscope sensor. Next, they heated an adsorbate-covered surface to 600 millikelvin and then moved the sensor tipped with the single molecule close to the surface and read the signals received by the probe as the two molecules interacted.

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Dennis Danzik has invented a whirligig that calls for the suspension of disbelief and the laws of physics. If it works as advertised, it would rank with the harnessing of steam, electricity and the atom.