Physics News and Discussions

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New optical antennas harvest 100 times more electricity from heat

27 May 2021 | 19:37 GMT

The world's most efficient optical rectennas yet can harvest over 100 times more energy from waste heat compared to previous devices, although a new study finds that much work is needed before they can achieve practical value.

Rectennas—short for "rectifying antennas"—pick up electromagnetic waves much like car antennas. When a rectenna’s antenna receives a signal, it generates oscillating charges that move through attached rectifier diodes. These rectifiers then convert these fluctuations to a direct electric current.

In theory, rectennas could harvest energy from heat that would ordinarily go to waste. "It would be great if these could help out with climate change," says study lead author Amina Belkadi, an electrical engineer at the University of Colorado at Boulder. "You could imagine adding them to solar cells so you can get even more energy from them."

However, the conversion efficiency of optical rectennas has proven far too low to make them useful for such applications. The problem is that in order to capture thermal radiation, rectennas have to be extraordinarily tiny, but the smaller they are, the more their resistance grows, which can shrink their power output.

Now Belkadi and her colleagues have found a way to dramatically boost optical rectenna efficiency using a quantum effect roughly equivalent to electrons walking through walls.

https://spectrum.ieee.org/tech-talk/ene ... l-rectenna


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Lasers capable of transmitting signals at 224 gigabits per second, enough to achieve 800 gigabit ethernet

June 4, 2021
With the massive proliferation of data-heavy services, including high-resolution video streaming and conferencing, cloud services infrastructure growth in 2021 is expected to reach a 27% CAGR. Consequently, while 400 gigabit ethernet (GbE) is currently enjoying widespread deployment, 800 GbE is poised to rapidly follow to address these bandwidth demands.

One approach to 800 GbE is to install eight 100 gigabit per second (Gbps) optical interfaces or lanes. As an alternative to reduce the hardware count, increase reliability, and lower cost, a team of researchers at Lumentum developed an optical solution that uses four 200 Gbps wavelength lanes to reach 800 GbE.

Syunya Yamauchi, a principal optical engineer at Lumentum, will present the optimized design during a session at the Optical Fiber Communication Conference and Exhibition (OFC), being held virtually from 06-11 June, 2021.
https://phys.org/news/2021-06-lasers-ca ... gabit.html
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New form of silicon could enable next-gen electronic and energy devices
June 4, 2021

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A team led by Carnegie's Thomas Shiell and Timothy Strobel developed a new method for synthesizing a novel crystalline form of silicon with a hexagonal structure that could potentially be used to create next-generation electronic and energy devices with enhanced properties that exceed those of the "normal" cubic form of silicon used today.

Their work is published in Physical Review Letters.

Silicon plays an outsized role in human life. It is the second most abundant element in the Earth's crust. When mixed with other elements, it is essential for many construction and infrastructure projects. And in pure elemental form, it is crucial enough to computing that the longstanding technological hub of the U.S.—California's Silicon Valley—was nicknamed in honor of it.

Like all elements, silicon can take different crystalline forms, called allotropes, in the same way that soft graphite and super-hard diamond are both forms of carbon. The form of silicon most commonly used in electronic devices, including computers and solar panels, has the same structure as diamond. Despite its ubiquity, this form of silicon is not actually fully optimized for next-generation applications, including high-performance transistors and some photovoltaic devices.
https://phys.org/news/2021-06-silicon-e ... nergy.html
“People assume that time is a strict progression of cause to effect, but *actually* from a non-linear, non-subjective viewpoint - it's more like a big ball of wibbly wobbly... time-y wimey... stuff.” - Steven Moffat
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Scientist are building a 100 petawatt laser to rip apart empty space and produce matter out of the vacuum
According to a report by Explica.co, The Station of Extreme Light, which China has been developing in Shanghai since 2018, has made significant progress in its goal of manufacturing lasers so powerful by 2023 that they could break through empty space and create matter.

The Extreme Light Station (SEL) is a laser installation designed to produce a laser with 100 petawatts (PW) of maximum power (one petawatt equals one thousand trillion watts), a goal that is expected to be achieved within two years.

Once completed, the laser will be the most powerful on Earth, with a power 10,000 times greater than that of all the electrical networks in the world combined and with an intensity 10 trillion times greater than that of sunlight, the report said.

The laser will be powerful enough to produce matter and antimatter directly from the vacuum of space, allowing us to observe in a terrestrial laboratory the same process that supposedly gave rise to the universe.

This technology is based on the fact that a vacuum is never really empty: it is like a pond filled with pairs of electrons and positrons (particles of matter and antimatter) that occasionally emerge to the surface (existence), although they annihilate each other as soon as they are formed.
And remember my friend, future events such as these will affect you in the future
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A quantum step to a heat switch with no moving parts
https://phys.org/news/2021-06-quantum.html
by Emily Caldwell, The Ohio State University
The cones in this image illustrate the equations of motion of electrons when an external magnetic field is applied to the bismuth alloy engineered for the study. Green lines and purple lines represent electrons that generate and absorb energy, respectively. Credit: Renee Ripley

Researchers have discovered a new electronic property at the frontier between the thermal and quantum sciences in a specially engineered metal alloy—and in the process identified a promising material for future devices that could turn heat on and off with the application of a magnetic "switch."

In this material, electrons, which have a mass in vacuum and in most other materials, move like massless photons or light—an unexpected behavior, but a phenomenon theoretically predicted to exist here. The alloy was engineered with the elements bismuth and antimony at precise ranges based on foundational theory.

Under the influence of an external magnetic field, the researchers found, these oddly behaving electrons manipulate heat in ways not seen under normal conditions. On both the hot and cold sides of the material, some of the electrons generate heat, or energy, while others absorb energy, effectively turning the material into an energy pump. The result: A 300% increase in its thermal conductivity.

Take the magnet away, and the mechanism is turned off.
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Researchers observe sound-light pulses in 2D materials for the first time
https://phys.org/news/2021-06-sound-lig ... rials.html
by Technion - Israel Institute of Technology

Using an ultrafast transmission electron microscope, researchers from the Technion—Israel Institute of Technology have, for the first time, recorded the propagation of combined sound and light waves in atomically thin materials.

The experiments were performed in the Robert and Ruth Magid Electron Beam Quantum Dynamics Laboratory headed by Professor Ido Kaminer, of the Andrew and Erna Viterbi Faculty of Electrical & Computer Engineering and the Solid State Institute.

Single-layer materials, alternatively known as 2D materials, are in themselves novel materials, solids consisting of a single layer of atoms. Graphene, the first 2D material discovered, was isolated for the first time in 2004, an achievement that garnered the 2010 Nobel Prize. Now, for the first time, Technion scientists show how pulses of light move inside these materials. Their findings, "Spatiotemporal Imaging of 2D Polariton Wavepacket Dynamics Using Free Electrons," were published in Science.
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Particle seen switching between matter and antimatter at CERN
By Michael Irving
June 09, 2021
A subatomic particle has been found to switch between matter and antimatter, according to Oxford physicists analyzing data from the Large Hadron Collider. It turns out that an unfathomably tiny weight difference between two particles could have saved the universe from annihilation soon after it began.

Antimatter is kind of the “evil twin” of normal matter, but it’s surprisingly similar – in fact, the only real difference is that antimatter has the opposite charge. That means that if ever a matter and antimatter particle come into contact, they will annihilate each other in a burst of energy.

To complicate things, some particles, such as photons, are actually their own antiparticles. Others have even been seen to exist as a weird mixture of both states at the same time, thanks to the quantum quirk of superposition (illustrated most famously through the thought experiment of Schrödinger’s cat.) That means that these particles actually oscillate between being matter and antimatter.
https://newatlas.com/physics/charm-meso ... ntimatter/
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Researchers build first modular quantum brain sensor, record signal
June 11, 2021

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A team of scientists at the University of Sussex have for the first time built a modular quantum brain scanner, and used it to record a brain signal. This is the first time a brain signal has been detected using a modular quantum brain sensor anywhere in the world. It's a major milestone for all researchers working on quantum brain imaging technology because modular sensors can be scaled up, like Lego bricks. The team have also connected two sensors like Lego bricks, proving that whole-brain scanning using this method is within reach—as detailed in their paper, which is published today in pre-print. This has not been possible with the currently commercially available quantum brain sensors from the United States.

These modular devices work like play bricks in that they can be connected together. This opens up the potential for whole-brain scanning using quantum technology, and potential advances for neurodegenerative diseases like Alzheimer's.

The device, which was built at the Quantum Systems and Devices laboratory at the university, uses ultra-sensitive quantum sensors to pick up these tiniest of magnetic fields to see inside the brain in order to map the neural activity.

The team applied the sensors to outside of a participant's scalp, close to the visual cortex of the brain. They asked the participant to open and close their eyes at 10–20 second intervals, and were able to detect a signal. This is a very simple action, but to see it happening inside the brain—from the outside—requires hugely sophisticated quantum technology.
https://phys.org/news/2021-06-modular-q ... ensor.html
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Physicists bring human-scale object to near standstill, reaching a quantum state
https://phys.org/news/2021-06-physicist ... state.html
by Sarah McDonnell, Massachusetts Institute of Technology
To the human eye, most stationary objects appear to be just that—still, and completely at rest. Yet if we were handed a quantum lens, allowing us to see objects at the scale of individual atoms, what was an apple sitting idly on our desk would appear as a teeming collection of vibrating particles, very much in motion.

In the last few decades, physicists have found ways to super-cool objects so that their atoms are at a near standstill, or in their "motional ground state." To date, physicists have wrestled small objects such as clouds of millions of atoms, or nanogram-scale objects, into such pure quantum states.

Now for the first time, scientists at MIT and elsewhere have cooled a large, human-scale object to close to its motional ground state. The object isn't tangible in the sense of being situated at one location, but is the combined motion of four separate objects, each weighing about 40 kilograms. The "object" that the researchers cooled has an estimated mass of about 10 kilograms, and comprises about 1x1026, or nearly 1 octillion, atoms.
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New possibilities for detecting Hawking radiation emitted by primordial black holes
https://phys.org/news/2021-06-possibili ... black.html
by Ingrid Fadelli , Phys.org
While many physicists have predicted the existence of dark matter, a type of matter that does not absorb, reflect or emit light, so far no one has been able to observe it experimentally or determine its fundamental nature. Light primordial black holes (PBHs), black holes the formed in the early universe, are among the most promising dark matter candidates. However, the existence of these black holes has not yet been confirmed.

Researchers at University of Amsterdam and University of California- Santa Cruz have recently carried out a study aimed at improving existing constraints on the allowed parameter space of PBHs as dark matter. In their paper, published in Physical Review Letters, they also propose a possible method that could be used to directly detect Hawking radiation in dark matter dense regions and potentially enable the discovery of PBH dark matter.
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