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Category: particle physics

It may be possible in the future to use information technology where electron spin is used to store, process and transfer information in quantum computers. It has long been the goal of scientists to be able to use spin-based quantum information technology at room temperature. A team of researchers from Sweden, Finland and Japan have now constructed a semiconductor component in which information can be efficiently exchanged between electron spin and light at room temperature and above. The new method is described in an article published in Nature Photonics.

It is well known that electrons have a negative charge; they also have another property called spin. This may prove instrumental in the advance of . To put it simply, we can imagine the electron rotating around its own axis, similar to the way in which the Earth rotates around its own axis. Spintronics—a promising candidate for future information technology—uses this quantum property of electrons to store, process and transfer information. This brings important benefits, such as higher speed and lower energy consumption than traditional electronics.

Developments in spintronics in recent decades have been based on the use of metals, and these have been highly significant for the possibility of storing large amounts of data. There would, however, be several advantages in using spintronics based on semiconductors, in the same way that semiconductors form the backbone of today’s electronics and photonics.

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Classical hydrodynamics laws can be very useful for describing the behavior of systems composed of many particles (i.e., many-body systems) after they reach a local state of equilibrium. These laws are expressed by so-called hydrodynamical equations, a set of mathematical equations that describe the movement of water or other fluids.

Researchers at Oak Ridge National Laboratory and University of California, Berkeley (UC Berkeley) have recently carried out a study exploring the hydrodynamics of a quantum Heisenberg spin-1/2 chain. Their paper, published in Nature Physics, shows that the spin dynamics of a 1D Heisenberg antiferromagnet (i.e., KCuF3) could be effectively described by a dynamical exponent aligned with the so-called Kardar-Parisi-Zhang universality class.

“Joel Moore and I have known each other for many years and we both have an interest in quantum magnets as a place where we can explore and test new ideas in physics; my interests are experimental and Joel’s are theoretical,” Alan Tennant, one of the researchers who carried out the study, told Phys.org. “For a long time, we have both been interested in temperature in quantum systems, an area where a number of really new insights have come along recently, but we had not worked together on any projects.”

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Circa 2020

Lasing—the emission of a collimated light beam of light with a well-defined wavelength (color) and phase—results from a self-organization process, in which a collection of emission centers synchronizes itself to produce identical light particles (photons). A similar self-organized synchronization phenomenon can also lead to the generation of coherent vibrations—a phonon laser, where phonon denotes, in analogy to photons, the quantum particles of sound.

Photon lasing was first demonstrated approximately 60 years ago and, coincidentally, 60 years after its prediction by Albert Einstein. This stimulated emission of amplified found an unprecedented number of scientific and technological applications in multiple areas.

Although the concept of a “laser of sound” was predicted almost at the same time, only few implementations have so far been reported and none has attained technological maturity. Now, a collaboration between researchers from Instituto Balseiro and Centro Atómico in Bariloche (Argentina) and Paul-Drude-Institut in Berlin has introduced a novel approach for the efficient generation of coherent vibrations in the tens of GHz range using semiconductor structures. Interestingly, this approach to the generation of coherent phonons is based on another of Einstein’s predictions: that of the 5th state of matter, a Bose-Einstein condensate (BEC) of coupled light-matter particles (polaritons).

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Circa 2014 essentially this could make endless computer chips from light.

Princeton researchers have managed to cause light to behave like a crystal within a specialized computer chip, according to a recent paper. This is the first time anyone has accomplished this effect in a lab.

Here’s why it’s so hard: Atoms can easily form solids, liquids, and gasses, because when they come into contact they push and pull on each other. That push and pull forms the underlying structure of all matter. Light particles, or photons, do not typically interact with one another, according to Dr. Andrew Houck, a professor of electrical engineering at Princeton and an author on the study. The trick of this research was forcing them to do just that.

“We build essentially an artificial atom, using lots of atoms acting in concert,” Houck tells Popular Science, “What emerges is a quantum mechanical object that [at about half a millimeter] is visible on the classical scale.”

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The New York Times Apr 09, 2021 17:29:04 IST

Evidence is mounting that a tiny subatomic particle seems to be disobeying the known laws of physics, scientists announced Wednesday, a finding that would open a vast and tantalizing hole in our understanding of the universe. The result, physicists say, suggests that there are forms of matter and energy vital to the nature and evolution of the cosmos that are not yet known to science.

“This is our Mars rover landing moment,” said Chris Polly, a physicist at the Fermi National Accelerator Laboratory, or Fermilab, in Batavia, Illinois, who has been working toward this finding for most of his career.

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Two teams of researchers have independently found that there exists a certain type of graphene system where electrons freeze as the temperature rises. The first team, with members from Israel, the U.S. and Japan, found that placing one layer of graphene atop another and then twisting the one on top resulted in a graphene state in which the electrons would freeze as temperatures rose. And in attempting to explain what they observed, they discovered that the entropy of the near-insulating phase was approximately half of what would be expected from free-electron spins. The second team, with members from the U.S., Japan and Israel, found the same graphene system and in their investigation to understand their observations, they noted that a large magnetic moment arose in the insulator. Both teams have published their results in the journal Nature. Biao Lian with Princeton University has published a News and Views piece outlining the work by both teams in the same journal issue.

As temperatures around most substances rise, the particles they are made of are excited. This results in solids melting to liquids and liquids turning to a gas. This is explained by thermodynamics—higher temperatures lead to more , which is a description of disorder. In this new effort, both teams found an exception to this rule—a graphene system in which electrons freeze as the .

The graphene system was very simple. Both teams simply laid one sheet of on top of another and then twisted the top sheet very slightly. But it had to be twisted at what they describe as the “magic angle,” describing a twist of just 1 degree. The moiré pattern that resulted led to lower velocity of the electrons in the system, which in turn led to more resistance, bringing the system close to being an insulator.

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Researchers have used a quantum mechanical property to overcome some of the limitations of conventional holograms. The new approach, detailed in Nature Physics, employed quantum entanglement, allowing two photons to become a single “non-local particle.” A series of entangled photon pairs is key to producing new and improved holograms.

Classical holograms work by using a single light beam split into two. One beam is sent towards the object you’re recreating and is reflected onto a special camera. The second beam is sent directly onto the camera. By measuring the differences in light, its phase, you can reconstruct a 3D image. A key property in this is the wave’s coherence.

The quantum hologram shares some of these principles but its execution is very different. It starts by splitting a laser beam in two, but these two beams will not be reunited. The key is in the splitting. As you can see in the image below, the blue laser hits a nonlinear crystal, which creates two beams made of pairs of entangled photons.

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PARIS: Scientists believe they may have discovered a “brand-new force of nature” at CERN’s Large Hadron Collider that could explain why certain atomic particles behave unexpectedly and which may transform our understanding the rudiments of physics.

Authors of the research said this week that their results should “get physicists’ hearts beating just a little faster” after they discovered evidence of a “brand-new” type of particle.

Since its inception over a decade ago, the Large Hadron Collider (LHC) has sought to delve into the secrets of the universe by studying the smallest discreet particles of matter as they collide at nearly the speed of light.

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