Category: particle physics – Page 332
Tiny crystals, known as quantum dots, have enabled an international team to achieve a quantum efficiency exceeding 100 percent in the photocurrent generated in a hybrid inorganic-organic semiconductor.
Perovskites are exciting semiconductors for light-harvesting applications and have already shown some impressive performances in solar cells. But improvements in photo-conversion efficiency are necessary to take this technology to a broader market.
Light comes in packets of energy known as photons. When a semiconductor absorbs a photon, the electromagnetic energy is transferred to a negatively charged electron and its positively charged counterpart, known as a hole. An electric field can sweep these particles in opposite directions, thereby allowing a current to flow. This is the basic operation of a solar cell. It might sound simple, but optimizing the quantum efficiency, or getting as many electron-hole pairs from the incoming photons as possible, has been a long-standing goal.
Cold Fusion is possible by replacing Hydrogen Electrons with Muons.
- Takes 5GeV to create a Muon, they only live for 2.2 microseconds.
- Muons provide a catalyst for 150 fusion events, before sticking to Helium Atom.
- Net fusion output is 2.7GeV per 5GeV Muon.
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The received view in physics is that the direction of time is provided by the second law of thermodynamics, according to which the passage of time is measured by ever-increasing disorder in the universe. This view, Julian Barbour argues, is wrong. If we reject Newton’s faulty assumptions about the existence of absolute space and time, Newtonian dynamics can be shown to provide a very different arrow of time. Its direction, according to this theory, is given by the increase in the complexity and order of a system of particles, exactly the opposite of what the received view about time suggests.
Two of the most established beliefs of contemporary cosmology are that the universe is expanding and that the direction of the arrow of time in the universe is defined by ever-increasing disorder (entropy), as described by the second law of thermodynamics. But both of these beliefs rest on shaky ground. In saying that the universe is expanding, physicists implicitly assume its size is measured by a rod that exists outside the universe, providing an absolute scale. It’s the last vestige of Newton’s absolute space and should have no place in modern cosmology. And in claiming that entropy is what gives time its arrow, physicists uncritically apply the laws of thermodynamics, originally discovered through the study of steam engines, to the universe as a whole. That too needs to be questioned.
Einstein and why the block universe is a mistake Read more In the absence of an absolute space and external measuring rods, size is always relative — relative to a measure of distance internal to the system. Starting from the simplest case, a triangle, what we find is that the internal measure of size produces a ratio which also happens to be related to a mathematical measure of complexity that intriguingly plays the central role in Newtonian universal gravitation. Applying these findings to the universe as a whole, we find that Newton’s theory of gravity, contrary to what physicists believe, contains within it an intrinsic arrow of time. This provides a strong hint that the direction of time is not defined by an increase in entropy, but by an increase in structure and complexity.
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The University of Innsbruck, Austria, realized a quantum computer that breaks out of this paradigm and unlocks additional computational resources, hidden in almost all of today’s quantum devices. Computers are well-known for operating with binary information, or zeros and ones, which has led to computers powering so much. This new approach results in more computational power with fewer quantum particles.
Quantum computers work with more than zero and one and digital computers work with zeros and ones, also called binary information. Quantum computers are also designed with binary information processing in mind. In fact, it was so successful that computers now power everything from coffee makers to self-driving cars, and it’s hard to imagine life without them. Restricting researchers to binary systems prevent these devices from living up to their true potential.
The research team succeeded in developing a quantum computer that can perform arbitrary calculations with so-called quantum digits, thereby unlocking more computational power with fewer quantum particles. Unlike the classical method, the new method that utilizes more states does not negatively impact the reliability of the computer. The researchers have developed a quantum computer that can make use of the full potential of these atoms.
Physicists are (temporarily) augmenting reality to crack the code of quantum systems.
Predicting the properties of a molecule or material requires calculating the collective behavior of its electrons. Such predictions could one day help researchers develop new pharmaceuticals or design materials with sought-after properties such as superconductivity. The problem is that electrons can become “quantum mechanically” entangled with one another, meaning they can no longer be treated individually. The entangled web of connections becomes absurdly tricky for even the most powerful computers to unravel directly for any system with more than a handful of particles.
Now, quantum physicists at the Flatiron Institute’s Center for Computational Quantum Physics (CCQ) in New York City and the École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland have sidestepped the problem. They created a way to simulate entanglement by adding to their computations extra “ghost” electrons that interact with the system’s actual electrons.
Scientists from The University of Manchester have developed a novel yet simple method for producing vertical stacks of alternating superconductor and insulator layers of tantalum disulphide (TaS 2). The findings, from a team led by Professor Rahul Nair, could speed up the process of manufacturing such devices – so-called van der Waals heterostructures – with application in high-mobility transistors, photovoltaics and optoelectronics.
Van der Waals heterostructures are much sought after since they display many unique and useful properties not found in naturally occurring materials. In most cases, they are prepared by manually stacking one layer over the other in a time-consuming and labour-intensive process.
Electron microscopy image of the synthesized 6R TaS 2 with an atomic model of the material on the left. The brown spheres represent Ta atoms and the yellow spheres represent sulphur atoms. The atomic positions and arrangement in the microscopic image are an exact match with the model, confirming its structure. (Image: University of Manchester)
A special bonding state between atoms has been created in the laboratory for the first time: With a laser beam, atoms can be polarized so that they are positively charged on one side and negatively charged on the other. This makes them attract each other creating a very special bonding state—much weaker than the bond between two atoms in an ordinary molecule, but still measurable. The attraction comes from the polarized atoms themselves, but it is the laser beam that gives them the ability to do so—in a sense, it is a “molecule” of light and matter.
Theoretically, this effect has been predicted for a long time, but now scientists at the Vienna Center for Quantum Science and Technology (VCQ) at TU Wien, in cooperation with the University of Innsbruck, have succeeded in measuring this exotic atomic bond for the first time. This interaction is useful for manipulating extremely cold atoms, and the effect could also play a role in the formation of molecules in space. The results have now been published in the scientific journal Physical Review X.
Scientists have long wondered how birds “read” Earth’s magnetic field to navigate. Some think entangled particles in birds’ eyes play a role.
Atoms are notoriously difficult to control. They zigzag like fireflies, tunnel out of the strongest containers and jitter even at temperatures near absolute zero.
Nonetheless, scientists need to trap and manipulate single atoms in order for quantum devices, such as atomic clocks or quantum computers, to operate properly. If individual atoms can be corralled and controlled in large arrays, they can serve as quantum bits, or qubits—tiny discrete units of information whose state or orientation may eventually be used to carry out calculations at speeds far greater than the fastest supercomputer.
Researchers at the National Institute of Standards and Technology (NIST), together with collaborators from JILA—a joint institute of the University of Colorado and NIST in Boulder—have for the first time demonstrated that they can trap single atoms using a novel miniaturized version of “optical tweezers”—a system that grabs atoms using a laser beam as chopsticks.