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Category: particle physics – Page 446

A speed limit also applies in the quantum world

Even in the world of the smallest particles with their own special rules, things cannot proceed infinitely fast. Physicists at the University of Bonn have now shown what the speed limit is for complex quantum operations. The study also involved scientists from MIT, the universities of Hamburg, Cologne and Padua, and the Jülich Research Center. The results are important for the realization of quantum computers, among other things. They are published in the prestigious journal Physical Review X, and covered by the Physics Magazine of the American Physical Society.

Generating photons for communication in a quantum computing system

8 oct 2020.

MIT researchers using superconducting quantum bits connected to a microwave transmission line have shown how the qubits can generate on demand the photons, or particles of light, necessary for communication between quantum processors.

Twisted trilayer graphene could help make high-temperature superconductors

Two’s company, but three’s a crowd – unless you’re trying to make graphene superconduct at higher temperatures. That is the finding of researchers at Harvard University in the US, who discovered that the superconducting state in three stacked and twisted layers of graphene is more robust to temperature increase than the equivalent state in two-layer graphene. The researchers also found evidence that superconductivity in the trilayer system comes from strong interactions between electrons, rather than weak ones as in most conventional superconductors – corroborating a result reported a few days earlier by a separate team at the Massachusetts Institute of Technology (MIT).

A sheet of graphene consists of a simple repetition of carbon atoms arranged in a two-dimensional hexagonal lattice. When two sheets of graphene are placed atop each other and slightly misaligned, they form a moiré pattern, or “stretched” superlattice that dramatically changes the electronic interactions in the material compared to its pristine counterpart. The misalignment angle is critical: in 2018, the MIT group, led by Pablo Jarillo-Herrero, discovered a so-called “magic” angle of 1.1° where the material switches from an insulator to a superconductor. This means the twisted graphene can carry electrical current with no resistance below a superconducting transition temperature, Tc, of 1.7 K.

Counter-Intuitive Quantum Mechanics: State of Vibration That Exists Simultaneously at Two Different Times

When Light and Atoms Share a Common Vibe

An especially counter-intuitive feature of quantum mechanics is that a single event can exist in a state of superposition — happening both here and there, or both today and tomorrow.

Such superpositions are hard to create, as they are destroyed if any kind of information about the place and time of the event leaks into the surrounding — and even if nobody actually records this information. But when superpositions do occur, they lead to observations that are very different from that of classical physics, questioning down to our very understanding of space and time.

The Universe’s 7 biggest mysteries (and why they’re unsolved)

In the last decade, we’ve taken photos of a black holes, peered into the heart of atoms and looked back at the birth of the Universe. And yet, there are yawning gaps in our understanding of the Universe and the laws that govern it. These are the mysteries that will be troubling physicists and astronomers over the next decade and beyond.

Dark matter, the nature of time, aliens and supermassive black holes: these seven things will be puzzling astronomers for years to come.

Scientists Use Lithium To Control Heat In Nuclear Fusion Reactors

Researchers unlocked the electronic properties of graphene by folding the material like origami paper.

Researchers at the US Department of Energy’s Princeton Plasma Physics Laboratory have created a plan using liquid lithium to control the extreme heat that could strike the exhaust system inside tokamak fusion reactors.

A tokamak is a confinement device that uses a powerful magnetic field to confine plasma in the shape of a torus and whose work is to produce controlled thermonuclear fusion power.

Fusion, on the other hand, is the nuclear reaction that occurs when atoms collide and fuse together, releasing huge amounts of energy. This process is what powers the Sun.

A Magnetic Twist to Graphene Could Offer a Dramatic Increase in Processing Speeds Compared to Electronics

Electrons in materials have a property known as ‘spin’, which is responsible for a variety of properties, the most well-known of which is magnetism. Permanent magnets, like the ones used for refrigerator doors, have all the spins in their electrons aligned in the same direction. Scientists refer to this behavior as ferromagnetism, and the research field of trying to manipulate spin as spintronics.

Down in the quantum world, spins can arrange in more exotic ways, giving rise to frustrated states and entangled magnets. Interestingly, a property similar to spin, known as “the valley,” appears in graphene materials. This unique feature has given rise to the field of valleytronics, which aims to exploit the valley property for emergent physics and information processing, very much like spintronics relies on pure spin physics.

Swirlonic Super Particles: Physicists Baffled by a Novel State of Matter

A novel state of matter has been discovered by physicists at the University of Leicester.

In recent years, active, self-propelled particles have received growing interest amongst the scientific community. Examples of active particles and their systems are numerous and very diverse, ranging from bacterium films to flocks of birds or human crowds. These systems can demonstrate unusual behavior, which is challenging to understand or model.

To this end, large-scale models of active particles were being scrutinized by experts at Leicester, in order to understand basic principles underlying active particle dynamics and apply them in a scenario of an evacuation strategy for customers in crowded place. Unexpectedly, the ‘super-particles’ milling in a circular motion were stumbled upon by Leicester’s physicists who subsequently coined the phenomenon as “swirlonic.”