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Category: particle physics

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 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 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.

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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 by altering the size, shape and spacing of to design gradient-index lenses that guide and on the microscale. The 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 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 , the researchers first absorbed magnetic 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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Tunneling, a key feature of quantum mechanics, is when a particle that encounters a seemingly insurmountable barrier passes through it, ending up on the other side. A series of experiments carried out by physicists from Griffith University, Lanzhou University, the Australian National University, Drake University and Korea’s Institute for Basic Science has definitively determined the tunneling delay, which is also the time it takes for an electron to get out or ionize from a hydrogen atom.

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Scientists working at the Fermi National Accelerator Laboratory (Fermilab) near Chicago have successfully communicated a short digital message using a stream of neutrinos. While this sounds cool, the truly exceptional bit is that the message was transmitted through 790 feet (240m) of solid stone.

Neutrinos are subatomic particles (like electrons or quarks, or the theorized Higgs boson) that have almost zero mass, a neutral charge (thus their name), and travel at close to the speed of light. Unlike almost every other particle in the universe, neutrinos are unaffected by electromagnetism (because of their neutral charge), and only subject to gravity and weak nuclear force. This means that neutrinos can easily pass through solid objects as large as planets. Every second, 65 billion neutrinos from the Sun pass through each square centimeter of the Earth at almost the speed of light.

To recreate this effect, the Fermilab scientists used a particle accelerator (NuMI) to shoot a stream of neutrinos through 240 meters of stone at the MINERvA neutrino detector. If MINERvA detected neutrinos, it registered as a binary 1; no neutrinos, binary 0. Using this technique (pictured above), the scientists, with a burst of originality to rival Alexander Graham Bell himself, transmitted the word “neutrino.”

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With a quantum coprocessor in the cloud, physicists from Innsbruck, Austria, open the door to the simulation of previously unsolvable problems in chemistry, materials research or high-energy physics. The research groups led by Rainer Blatt and Peter Zoller report in the journal Nature how they simulated particle physics phenomena on 20 quantum bits and how the quantum simulator self-verified the result for the first time.

Many scientists are currently working on investigating how quantum advantage can be exploited on hardware already available today. Three years ago, physicists first simulated the spontaneous formation of a pair of elementary particles with a digital quantum computer at the University of Innsbruck. Due to the error rate, however, more complex simulations would require a large number of quantum bits that are not yet available in today’s quantum computers. The analog simulation of quantum systems in a quantum computer also has narrow limits. Using a new method, researchers around Christian Kokail, Christine Maier und Rick van Bijnen at the Institute of Quantum Optics and Quantum Information (IQOQI) of the Austrian Academy of Sciences have now surpassed these limits. They use a programmable ion trap quantum computer with 20 quantum bits as a quantum coprocessor, in which quantum mechanical calculations that reach the limits of classical computers are outsourced.

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