A pair of studies in Nature show that a quasiparticle, known as a plasmon polariton, can be pulled with and against a flow of electrons, a finding that could lead to more efficient ways of manipulating light at the nanoscale.
In the depths of space, there are celestial bodies where extreme conditions prevail: Rapidly rotating neutron stars generate super-strong magnetic fields. And black holes, with their enormous gravitational pull, can cause huge, energetic jets of matter to shoot out into space. An international physics team with the participation of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) has now proposed a new concept that could allow some of these extreme processes to be studied in the laboratory in the future: A special setup of two high-intensity laser beams could create conditions similar to those found near neutron stars. In the discovered process, an antimatter jet is generated and accelerated very efficiently. The experts present their concept in the journal Communications Physics.
The basis of the new concept is a tiny block of plastic, crisscrossed by micrometer-fine channels. It acts as a target for two lasers. These simultaneously fire ultra-strong pulses at the block, one from the right, the other from the left — the block is literally taken by laser pincers. “When the laser pulses penetrate the sample, each of them accelerates a cloud of extremely fast electrons,” explains HZDR physicist Toma Toncian. “These two electron clouds then race toward each other with full force, interacting with the laser propagating in the opposite direction.” The following collision is so violent that it produces an extremely large number of gamma quanta — light particles with an energy even higher than that of X-rays.
The swarm of gamma quanta is so dense that the light particles inevitably collide with each other. And then something crazy happens: According to Einstein’s famous formula E=mc2, light energy can transform into matter. In this case, mainly electron-positron pairs should be created. Positrons are the antiparticles of electrons. What makes this process special is that “very strong magnetic fields accompany it,” describes project leader Alexey Arefiev, a physicist at the University of California at San Diego. “These magnetic fields can focus the positrons into a beam and accelerate them strongly.” In numbers: Over a distance of just 50 micrometers, the particles should reach an energy of one gigaelectronvolt (GeV) — a size that usually requires a full-grown particle accelerator.
One of the most important open questions in science is how our consciousness is established. In the 1990s, long before winning the 2020 Nobel Prize in Physics for his prediction of black holes, physicist Roger Penrose teamed up with anaesthesiologist Stuart Hameroff to propose an ambitious answer.
They claimed that the brain’s neuronal system forms an intricate network and that the consciousness this produces should obey the rules of quantum mechanics —the theory that determines how tiny particles like electrons move around. This, they argue, could explain the mysterious complexity of human consciousness.
A novel, high-resolution fluorescence imaging technique reveals a pattern, known as a Pauli crystal, that can emerge in a cloud of trapped, noninteracting fermions.
Bring two particles together and, in general, they will interact. For example, two electrons will repel each other through electrostatic forces, or two atoms may form a molecule through electrostatic and van der Waals forces. Noninteracting particles, however, can also affect another’s behavior in a way that depends on the spin of both particles. In particular, fermionic particles, which have half-integer spin, obey the Pauli exclusion principle, which states that two fermions can never occupy the same quantum state. Two electrons in an atom, for instance, can never occupy the same quantum state. As a result, noninteracting particles can form self-organized structures. However, these structures, called Pauli crystals, have not been previously observed. Now using ultracold atoms, Marvin Holten from the University of Heidelberg, Germany, and colleagues have experimentally realized and imaged a Pauli crystal [1].
The tool next examines how one protein’s amino acids interact with another within the same protein, for example, by examining the distance between two distant building blocks. It’s like looking at your hands and feet fully stretched out, versus in a backbend measuring the distance between those extremities as you “fold” into a yoga pose.
Finally, the third track looks at 3D coordinates of each atom that makes up a protein building block—kind of like mapping the studs on a Lego block—to compile the final 3D structure. The network then bounces back and forth between these tracks, so that one output can update another track.
The end results came close to those of DeepMind’s tool, AlphaFold2, which matched the gold standard of structures obtained from experiments. Although RoseTTAFold wasn’t as accurate as AlphaFold2, it seemingly required much less time and energy. For a simple protein, the algorithm was able to solve the structure using a gaming computer in about 10 minutes.
One of the most important open questions in science is how our consciousness is established. In the 1990s, long before winning the 2020 Nobel Prize in Physics for his prediction of black holes, physicist Roger Penrose teamed up with anaesthesiologist Stuart Hameroff to propose an ambitious answer.
They claimed that the brain’s neuronal system forms an intricate network and that the consciousness this produces should obey the rules of quantum mechanics – the theory that determines how tiny particles like electrons move around. This, they argue, could explain the mysterious complexity of human consciousness.
Continue reading “Can Consciousness Be Explained by Quantum Physics?” »
Circa 1999 could lead to a sorta room temperature hydrogen fill up.
Masses of single-walled carbon nanotubes (SWNTs) with a large mean diameter of about 1.85 nanometers, synthesized by a semicontinuous hydrogen arc discharge method, were employed for hydrogen adsorption experiments in their as-prepared and pretreated states. A hydrogen storage capacity of 4.2 weight percent, or a hydrogen to carbon atom ratio of 0.52, was achieved reproducibly at room temperature under a modestly high pressure (about 10 megapascal) for a SWNT sample of about 500 milligram weight that was soaked in hydrochloric acid and then heat-treated in vacuum. Moreover, 78.3 percent of the adsorbed hydrogen (3.3 weight percent) could be released under ambient pressure at room temperature, while the release of the residual stored hydrogen (0.9 weight percent) required some heating of the sample.
Experiments now online or being built in Japan, South Korea, Italy, Canada and the United States are an order of magnitude more sensitive than the previous generation, and planned future detectors would improve on that by another two orders of magnitude (see ‘Experiments around the world’). In 2015, an advisory committee to the US Department of Energy identified such a project as a priority and a commitment to fund an experiment to detect Majorana neutrinos — estimated to cost up to/around US$250 million — is thought to be imminent.
The search for exotic ‘Majorana’ particles that could solve a big antimatter mystery is ramping up around the world.
The Juno Waves instrument “listened” to the radio emissions from Jupiter’s immense magnetic field to find their precise locations.
By listening to the rain of electrons flowing onto Jupiter from its intensely volcanic moon Io, researchers using NASA’s Juno spacecraft have found what triggers the powerful radio emissions within the monster planet’s gigantic magnetic field. The new result sheds light on the behavior of the enormous magnetic fields generated by gas-giant planets like Jupiter.
Continue reading “Juno tunes into radio noise triggered by Jupiter’s volcanic moon Io” »
Researchers at ETH Zurich have trapped a tiny sphere measuring a hundred nanometres using laser light and slowed down its motion to the lowest quantum mechanical state. This technique could help researchers to study quantum effects in macroscopic objects and build extremely sensitive sensors.
Why can atoms or elementary particles behave like waves according to quantum physics, which allows them to be in several places at the same time? And why does everything we see around us obviously obey the laws of classical physics, where such a phenomenon is impossible? In recent years, researchers have coaxed larger and larger objects into behaving quantum mechanically. One consequence of this is that, when passing through a double slit, these objects form an interference pattern that is characteristic of waves.
Up to now, this could be achieved with molecules consisting of a few thousand atoms. However, physicists hope one day to be able to observe such quantum effects with properly macroscopic objects. Lukas Novotny, professor of photonics, and his collaborators at the Department of Information Technology and Electrical Engineering at ETH Zurich have now made a crucial step in that direction. Their results were recently published in the scientific journal Nature.
