Category Archives: Quantum Physics

The case for quantum mechanics operating at the macro level is growing.

Observable in human behaviour, societal trends and global phenomena, a quantum perspective allows new insights into international relations, world politics and global systems.

But it also poses a fundamental challenge to what we know about ourselves and the world around us.

With the support of the Carnegie Corporation of New York, Project Q continues to bring the leading thinkers and practitioners together to grapple with these ideas and shape the path forward.

Project Q's 'Quantizing International Relations', a special issue of Security Dialogue edited by James Der Derian and Alexander Wendt, is available online now.

Project Q is an initiative of the Centre for International Security Studies, led by Professor James Der Derian. An expanded collected volume of essays, to be published by the Oxford University Press, and a feature-length documentary film, Project Q: War, Peace and Quantum Mechanics, will appear in 2021.

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International Relations goes quantum - News - The University of Sydney

It's not often we pause in the middle of our day and think about the nature of viscosity, unless perhaps we're on our way to Oil Can Henry's for an oil change onthe 'ol family truckster. But thanks to some fluid-friendly physicists, now we've got a reason!

According to Princeton University's official definition, "Viscosityis a measure of a fluid's resistance to flow.It describes the internal friction of a moving fluid. A fluid with large viscosity resists motion because its molecular makeup gives it a lot of internal friction." Got that?

Now that we're all in agreement as to what constitutes resistant flow, imagine a free-moving substance, call it a "perfect fluid" that operates with the least possible amount of friction allowed by the immutable laws of quantum mechanics, and you'll grasp what scientists at MIT have just created. Far from just a friction-less environment, the results of the experiments might aid physicistsin theirpursuits to investigatethe viscosity in cores of neutron stars, the plasma of the ancientuniverse, and additional forcefulinteracting fluids.

To create this universal magic, scientists made a recording of sound waves delivered through a controlled gas of basic particles called fermions. This rising scale, known as a glissando, can be heard in the clip below, which demonstrates the distinct frequencies that the gas resonates like a guitar string when sound waves are injected.

By analyzingthousands of sound waves shootingthrough this gas to calculateits sound diffusion, or how fastsound dissipates, the team was able to determine thematerials viscosity, or internal friction. Theresults of their effortswere published this week in the online journal, Science.

Its quite difficult to listen to a neutron star, says study co-author Martin Zwierlein, the Thomas A. Frank Professor of Physics at MIT. But now you could mimic it in a lab using atoms, shake that atomic soup and listen to it, and know how a neutron star would sound.The stars resonant frequencies would be similar to those of the gas, and even audible if you could get your ear close without being ripped apart by gravity.

So low was the value of the sound diffusion that it could only be measuredby a molecular-level of friction. Itconfirmed that thisstrongly interacting fermion gas demonstrates propertiesofa perfect fluid, and is considered universal in nature. This marks the first instance ofscientistsmeasuringsound diffusion in a perfect fluid.

Fermions are elementary particles likeelectrons, protons, and neutrons, and areregarded asthe building blocks of all matter.Normally content to exist as loners, fermions display characteristics of low viscosity when aroused and made to strongly interact.To manufacture this unflawedfluid, the researchers employeda system of lasers to entrap a gas of lithium-6 atoms, which are recognized asfermions.

By configuringlasers to form an optical box around the fermion gas, scientists were able to tune them to causefermions to ricochet back into the box when they collided with the edges of the optical enclosure.

All these snapshots together give us a sonogram, and its a bit like whats done when taking an ultrasound at the doctors office, Zwierlein added. The quality of the resonances tells me about the fluids viscosity, or sound diffusivity. If a fluid has low viscosity, it can build up a very strong sound wave and be very loud, if hit at just the right frequency. If its a very viscous fluid, then it doesnt have any good resonances.

Zwierlein and his colleagues are confident that thesenew tools can be harnessed toestimate quantum friction withincosmicmatter likeneutron stars, and also allowfor a greaterunderstanding of howdiversematerials can be manipulatedto portrayperfect, superconducting flow.

This work connects directly to resistance in materials, Zwierlein notes. Having figured out whats the lowest resistance you could have from a gas tells us what can happen with electrons in materials, and how one might make materials where electrons could flow in a perfect way. Thats exciting.

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Scientists just engineered the perfect friction-less fluid and here's what it sounds like! - SYFY WIRE

Scientists have captured the sound of a perfect fluid, which flows with the smallest amount of friction allowed by the laws of quantum mechanics. Credit: Christine Daniloff, MIT

The results should help scientists study the viscosity in neutron stars, the plasma of the early universe, and other strongly interacting fluids.

For some, the sound of a perfect flow might be the gentle lapping of a forest brook or perhaps the tinkling of water poured from a pitcher. For physicists, a perfect flow is more specific, referring to a fluid that flows with the smallest amount of friction, or viscosity, allowed by the laws of quantum mechanics. Such perfectly fluid behavior is rare in nature, but it is thought to occur in the cores of neutron stars and in the soupy plasma of the early universe.

Now MIT physicists have created a perfect fluid in the laboratory, and found that it sounds something like this:

This recording is a product of a glissando of sound waves that the team sent through a carefully controlled gas of elementary particles known as fermions. The pitches that can be heard are the particular frequencies at which the gas resonates like a plucked string.

The researchers analyzed thousands of sound waves traveling through this gas, to measure its sound diffusion, or how quickly sound dissipates in the gas, which is related directly to a materials viscosity, or internal friction.

Surprisingly, they found that the fluids sound diffusion was so low as to be described by a quantum amount of friction, given by a constant of nature known as Plancks constant, and the mass of the individual fermions in the fluid.

This fundamental value confirmed that the strongly interacting fermion gas behaves as a perfect fluid, and is universal in nature. The results, published today in the journal Science, demonstrate the first time that scientists have been able to measure sound diffusion in a perfect fluid.

Scientists can now use the fluid as a model of other, more complicated perfect flows, to estimate the viscosity of the plasma in the early universe, as well as the quantum friction within neutron stars properties that would otherwise be impossible to calculate. Scientists might even be able to approximately predict the sounds they make.

Its quite difficult to listen to a neutron star, says Martin Zwierlein, the Thomas A. Frank Professor of Physics at MIT. But now you could mimic it in a lab using atoms, shake that atomic soup and listen to it, and know how a neutron star would sound.

While a neutron star and the teams gas differ widely in terms of their size and the speed at which sound travels through, from some rough calculations Zwierlein estimates that the stars resonant frequencies would be similar to those of the gas, and even audible if you could get your ear close without being ripped apart by gravity, he adds.

Zwierleins co-authors are lead author Parth Patel, Zhenjie Yan, Biswaroop Mukherjee, Richard Fletcher, and Julian Struck of the MIT-Harvard Center for Ultracold Atoms.

To create a perfect fluid in the lab, Zwierleins team generated a gas of strongly interacting fermions elementary particles, such as electrons, protons, and neutrons, that are considered the building blocks of all matter. A fermion is defined by its half-integer spin, a property that prevents one fermion from assuming the same spin as another nearby fermion. This exclusive nature is what enables the diversity of atomic structures found in the periodic table of elements.

If electrons were not fermions, but happy to be in the same state, hydrogen, helium, and all atoms, and we ourselves, would look the same, like some terrible, boring soup, Zwierlein says.

Fermions naturally prefer to keep apart from each other. But when they are made to strongly interact, they can behave as a perfect fluid, with very low viscosity. To create such a perfect fluid, the researchers first used a system of lasers to trap a gas of lithium-6 atoms, which are considered fermions.

The researchers precisely configured the lasers to form an optical box around the fermion gas. The lasers were tuned such that whenever the fermions hit the edges of the box they bounced back into the gas. Also, the interactions between fermions were controlled to be as strong as allowed by quantum mechanics, so that inside the box, fermions had to collide with each other at every encounter. This made the fermions turn into a perfect fluid.

We had to make a fluid with uniform density, and only then could we tap on one side, listen to the other side, and learn from it, Zwierlein says. It was actually quite diffult to get to this place where we could use sound in this seemingly natural way.

The team then sent sound waves through one side of the optical box by simply varying the brightness of one of the walls, to generate sound-like vibrations through the fluid at particular frequencies. They recorded thousands of snapshots of the fluid as each sound wave rippled through.

All these snapshots together give us a sonogram, and its a bit like whats done when taking an ultrasound at the doctors office, Zwierlein says.

In the end, they were able to watch the fluids density ripple in response to each type of sound wave. They then looked for the sound frequencies that generated a resonance, or an amplified sound in the fluid, similar to singing at a wine glass and finding the frequency at which it shatters.

The quality of the resonances tells me about the fluids viscosity, or sound diffusivity, Zwierlein explains. If a fluid has low viscosity, it can build up a very strong sound wave and be very loud, if hit at just the right frequency. If its a very viscous fluid, then it doesnt have any good resonances.

From their data, the researchers observed clear resonances through the fluid, particularly at low frequencies. From the distribution of these resonances, they calculated the fluids sound diffusion. This value, they found, could also be calculated very simply via Plancks constant and the mass of the average fermion in the gas.

This told the researchers that the gas was a perfect fluid, and fundamental in nature: Its sound diffusion, and therefore its viscosity, was at the lowest possible limit set by quantum mechanics.

Zwierlein says in addition to using the results to estimate quantum friction in more exotic matter, such as neutron stars, the results can be helpful in understanding how certain materials might be made to exhibit perfect, superconducting flow.

This work connects directly to resistance in materials, Zwierlein says. Having figured out whats the lowest resistance you could have from a gas tells us what can happen with electrons in materials, and how one might make materials where electrons could flow in a perfect way. Thats exciting.

Reference: Universal sound diffusion in a strongly interacting Fermi gas by Parth B. Patel, Zhenjie Yan, Biswaroop Mukherjee, Richard J. Fletcher, Julian Struck and Martin W. Zwierlein, 4 December 2020, Science.DOI: 10.1126/science.aaz5756

This research was supported, in part, by the National Science Foundation and the NSF Center for Ultracold Atoms, the Air Force Office of Scientific Research, the Office of Naval Research, and the David and Lucile Packard Foundation.

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MIT Physicists Created a Perfect Fluid and Captured the Sound Listen Here - SciTechDaily

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Using quantum physics, researchers are on the cusp of creating sensors that will see further, deeper, and around corners.

Since its inception at the start of the 20th Century, quantum physics has changed how we see the microscopic world. Thanks to advances in sensor technology, this revolutionary and counter-intuitive branch of physics could change our view of the everyday world.

Quantum sensors could be employed in medical scanners, self-driving vehicles, weather pattern assessments, and seismic activity analysis. Therefore, our understanding of the sometimes strange subatomic world is poised to change our everyday lives forever.

Such sensors manipulate aspects of quantum mechanics such as entanglementthe idea that a particle change can instantly influence its entangled partner despite the distance between themand the energy levels that electrons can occupy in atoms to assess the environment around them in devastatingly imaginative ways.

Beneath the surface of urban areas is a mass of utility infrastructures such as pipes, cables and sewers, transport utilities, and even mine shafts, old foundations, and sinkholes.

Public work in these areas is not just delayed and made more expensive by these buried obstacles, they can often pose a legitimate danger to workers and the general public. There are sensors that can probe beneath the ground without penetration. However, technology such as Ground Penetrating Radars (GPR) can only probe a few centimeters beneath the surface before its signal is stifled and pipes and cables can be meters deep.

One possible alternative comes from the quantum realm.

Quantum technology could create a gravity sensor which can detect much deeper beneath the surface. Theoretically, such a sensor could probe to the center of the Earth. Quantum gravity sensors are more useful as they do not send a signal through the ground. Instead, they measure density variations by using a facet of quantum physics known as superposition.

Superposition arises from particles' wave-like behavior and means that a quantum system can technically exist in two contradictory states at once. This contradictory existence continues until measurements are made.

A quantum gravity sensor would drop a cloud of supercooled atoms in a superposition of two different states into an area to be probed. Changes in the atomic cloud and how it passes through the ground are then observed, giving density measurements to the operators above the surface. These changes in density indicate buried obstacles such as pipes and cables, and voids caused by tunnels.

The application of such a system goes way beyond assisting in road works. A quantum gravity sensor could be used in volcanic activity areas to monitor lava flow and help geologists uncover water and mineral deposits. Self-piloted ships could also use the system to navigate and probe the depths of the ocean.

In the UK, the University of Birmingham has teamed with engineering services firm RSK on Gravity Pioneer a project that aims to make quantum gravity sensors a reality.

Self-navigation is a major problem for the car industry. The Insurance Institute for Highway Safety recently produced a report concluding that only one-third of crashes would be avoided by autonomous cars despite being impervious to human error, distraction or driver incapacitation.

The tendency of light to refract off walls and other surfaces can be used to build 3D images, as long as the sensors used to detect light are sensitive enough.This rebounded light could allow self-driving cars to see around corners. More sensitive sensors could also allow these vehicles to see through fog and smoke.

Improving the sensitivity of quantum sensors is one of the primary goals of scientists at the Pritzker School of Molecular Engineering (PME) at the University of Chicago.

The team believes that using a physics phenomenon called non-Hermitian dynamics can prevent a string of photonic cavities that prevent light from leaking from sensors. This results in an improvement in sensitivity without expending extra energy or vastly increasing the photon collection area of sensors.

Video Credit: University of Birmingham/YouTube.com

While quantum computers and even a quantum internet could be on the horizon, these improved information networks will rely heavily on accurate synchronized time-keeping. All the innovations discussed above will also hinge on hyper-accurate clocks over a geographically distributed network.

This precision timing is currently achieved using atomic clocks, which keep time with quantum phenomena and the randomness that lies at the heart of this field of physics. As such, they were probably the first piece of quantum tech to become widely available and probably warrant a mention in any discussion about such advance.

In addition to this, atomic clocks form the foundation of the Global Positioning Systems (GPS) technology that our satnavs and mobile phones rely on every day.

Atomic clocks combine a quartz crystal oscillator with an ensemble of atoms to achieve greater stability. To give you an idea of how accurate this makes them in comparison to a wristwatch that uses a quartz crystal oscillator alone, NASAs Deep Space Atomic Clock will be off by less than a nanosecond after four days and less than a microsecondone-millionth of a secondafter 10 years. This is equal to around one second every 10 million years.

Atomic clocks operate because electrons can only occupy certain energy levels while orbiting an atomic nucleus. They step from one level to another by absorbing or emitting a photon of specific energy.

Atomic clocks have incredible accuracy as photons come in precise packets of energy and it takes an exact amount of energy to make an electron step up.

However, that does not mean atomic clocks cannot be improved. NASA-funded researchers are attempting to use entanglement to create the most precise clock known to man.Entangling atoms in an atomic clock with enough atoms could produce an atomic clock so stable that it would lose a second about once every 30 billion years.

At the moment, these applicationsbarring atomic clocksare strictly in development phases, with some modalities further along than others. But the phenomena that inform these techniques are well established, and it is a matter of time before quantum sensors are market-ready.

In a recent Scientific American article, it was estimated that such sensors could be available in around 35 years.

To get a sense of how important quantum sensors are for the future, the University of Birmingham is leading an 80 million consortium, the UK Quantum Technology Hub for Sensors and Metrology, using quantum effects to build next-generation sensors for gravity, magnetic fields, rotation, time, THz radiation and quantum light.

Professor Kai Bongs, Director of Innovation at the College of Engineering and Physical Sciences at the University of Birmingham, is the consortium's principal investigator. He and his team have identified a market potential for quantum sensors of 4 billion per year, with the possibility of improving the UKs Gross Domestic Product by 10%.

Elsewhere in the UK, the government and private sector has invested 315 million into the second phase of its National Quantum Computing Program (20192024).

It is ironic perhaps that quantum physicsthe science of the very small, could, via quantum sensors, improve our lives in a very big way.

C Freier, M Hauth, V Schkolnik, B Leykauf, M Schilling, H Wziontek, H-G Scherneck, J Muller, and A Peters, (2020), Mobile quantum gravity sensor with unprecedented stability, Journal of Physics: Conference Series, doi:10.1088/17426596/723/1/012050

Young. J, (2020), Self-driving vehicles could struggle to eliminate most crashes, Insurance Institute for Highway Safety, https://www.iihs.org/news/detail/self-driving-vehicles-could-struggle-to-eliminate-most-crashes

McDonald. A., Clerk. A. A., (2020), Exponentially-enhanced quantum sensing with non-Hermitian lattice dynamics, Nature Communications, https://doi.org/10.1038/s41467-020-19090-4

What is an Atomic Clock? NASA JPL, https://www.nasa.gov/feature/jpl/what-is-an-atomic-clock

Are quantum sensors the key to transforming our lives? (2020), The University of Birmingham, https://www.birmingham.ac.uk/research/quest/emerging-frontiers/quantum-sensors.aspx

Disclaimer: The views expressed here are those of the author expressed in their private capacity and do not necessarily represent the views of AZoM.com Limited T/A AZoNetwork the owner and operator of this website. This disclaimer forms part of the Terms and conditions of use of this website.

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How Could Quantum Sensing Transform Industries and our Society? - AZoSensors

The Big Bang theory says that our universe began with a colossal explosion, about 14 billion years ago, and has been expanding and cooling ever since. Astronomers combine mathematical models with observations to develop workable theories of how the universe came to be, including Albert Einsteins general theory of relativity along with standard theories of fundamental particles. Today, NASA spacecraft such as the Hubble Space Telescope continue measuring the expansion of the universe.We can now tell an unbroken story, from inflation to the postinflation period, to the Big Bang and beyond, says David Kaiser, the Germeshausen Professor of the History of Science and professor of physics at MIT, about the postinflation reheating period that set up the conditions for the Big Bang, and in some sense puts the bang in the Big Bang. Its this bridge period where all hell breaks loose and matter behaves in anything but a simple way. We can trace a continuous set of processes, all with known physics, to say this is one plausible way in which the universe came to look the way we see it today.

Cosmic Inflation Lasted Less than a Trillionth of a Second

Just before the Big Bang launched the universe onto its ever-expanding course, physicists believe, there was another, more explosive phase of the early universe at play: cosmic inflation, which lasted less than a trillionth of a second. During this period, matter a cold, homogeneous goop inflated exponentially quickly before processes of the Big Bang took over to more slowly expand and diversify the infant universe.

The Big Bang Vanishes Scientists Doubt Most Famous Scientific Theory Since Einsteins Relativity

Recent observations have independently supported theories for both the Big Bang and cosmic inflation. But the two processes are so radically different from each other that scientists have struggled to conceive of how one followed the other.

All Hell Breaks Loose Bridging Cosmic Inflation with the Big Bang

Now physicists at MIT, Kenyon College, and elsewhere have simulated in detail an intermediary phase of the early universe that may have bridged cosmic inflation with the Big Bang, reports MIT. This phase, known as reheating, occurred at the end of cosmic inflation and involved processes that wrestled inflations cold, uniform matter into the ultrahot, complex soup that was in place at the start of the Big Bang.

The Extreme Energy that Drove Inflation

Kaiser and his colleagues simulated in detail how multiple forms of matter would have interacted during this chaotic period at the end of inflation. Their simulations show that the extreme energy that drove inflation could have been redistributed just as quickly, within an even smaller fraction of a second, and in a way that produced conditions that would have been required for the start of the Big Bang.

Quantum Effects Deviate from Theory of General Relativity

The team found this extreme transformation would have been even faster and more efficient if quantum effects modified the way that matter responded to gravity at very high energies, deviating from the way Einsteins theory of general relativity predicts matter and gravity should interact.

Alan Guths Theory Small Speck of Matter About a Hundred-Billionth the Size of a Proton

MIT theoretical physicist and cosmologist Alan Guth, who pioneered the theory that the universe dramatically expanded in size in a fleeting fraction of a second after the Big Bang famously said the Big Bang theory says nothing about what banged, why it banged, or what happened before it banged.

The theory of cosmic inflation, first proposed in the 1980s by Guth, the V.F. Weisskopf Professor of Physics, predicts that the universe began as an extremely small speck of matter, possibly about a hundred-billionth the size of a proton. This speck was filled with ultra-high-energy matter, so energetic that the pressures within generated a repulsive gravitational force the driving force behind inflation. Like a spark to a fuse, this gravitational force exploded the infant universe outward, at an ever-faster rate, inflating it to nearly an octillion times its original size (thats the number 1 followed by 26 zeroes), in less than a trillionth of a second.

Powering the Universe? Relic Light of the Big Bang Reveals an Exotic Unknown Force

Like a Spark to a Fuse

Like a spark to a fuse, this gravitational force exploded the infant universe outward, at an ever-faster rate, inflating it to nearly an octillion times its original size (thats the number 1 followed by 26 zeroes), in less than a trillionth of a second.

Kaiser and his colleagues attempted to work out what the earliest phases of reheating that bridge interval at the end of cosmic inflation and just before the Big Bang might have looked like.

The earliest phases of reheating should be marked by resonances. One form of high-energy matter dominates, and its shaking back and forth in sync with itself across large expanses of space, leading to explosive production of new particles, Kaiser says. That behavior wont last forever, and once it starts transferring energy to a second form of matter, its own swings will get more choppy and uneven across space. We wanted to measure how long it would take for that resonant effect to break up, and for the produced particles to scatter off each other and come to some sort of thermal equilibrium, reminiscent of Big Bang conditions.

The teams computer simulations, says MIT, represent a large lattice onto which they mapped multiple forms of matter and tracked how their energy and distribution changed in space and over time as the scientists varied certain conditions. The simulations initial conditions were based on a particular inflationary model a set of predictions for how the early universes distribution of matter may have behaved during cosmic inflation.

The scientists chose this particular model of inflation over others because its predictions closely match high-precision measurements of the cosmic microwave background a remnant glow of radiation emitted just 380,000 years after the Big Bang, which is thought to contain traces of the inflationary period.

A Slight Tweak Quantum Mechanics

The simulation tracked the behavior of two types of matter that may have been dominant during inflation, very similar to a type of particle, the Higgs boson, that was recently observed in other experiments.

Before running their simulations, the team added a slight tweak to the models description of gravity. While ordinary matter that we see today responds to gravity just as Einstein predicted in his theory of general relativity, matter at much higher energies, such as whats thought to have existed during cosmic inflation, should behave slightly differently, interacting with gravity in ways that are modified by quantum mechanics, or interactions at the atomic scale.

In Einsteins theory of general relativity, the strength of gravity is represented as a constant, with what physicists refer to as a minimal coupling, meaning that, no matter the energy of a particular particle, it will respond to gravitational effects with a strength set by a universal constant.

However, at the very high energies that are predicted in cosmic inflation, matter interacts with gravity in a slightly more complicated way. Quantum-mechanical effects predict that the strength of gravity can vary in space and time when interacting with ultra-high-energy matter a phenomenon known as nonminimal coupling.

Kaiser and his colleagues incorporated a nonminimal coupling term to their inflationary model and observed how the distribution of matter and energy changed as they turned this quantum effect up or down.

A Faster Transition

In the end they found that the stronger the quantum-modified gravitational effect was in affecting matter, the faster the universe transitioned from the cold, homogeneous matter in inflation to the much hotter, diverse forms of matter that are characteristic of the Big Bang.

By tuning this quantum effect, they could make this crucial transition take place over 2 to 3 e-folds, referring to the amount of time it takes for the universe to (roughly) triple in size. In this case, they managed to simulate the reheating phase within the time it takes for the universe to triple in size two to three times. By comparison, inflation itself took place over about 60 e-folds.

Reheating was an insane time, when everything went haywire, Kaiser says. We show that matter was interacting so strongly at that time that it could relax correspondingly quickly as well, beautifully setting the stage for the Big Bang. We didnt know that to be the case, but thats whats emerging from these simulations, all with known physics. Thats whats exciting for us.

Guth, the original architect for the theory of cosmic inflation, sees the groups results as an important new development in the study of inflationary models.

While versions of inflation based on a single form of matter give a remarkably good fit to observations, Dave and his collaborators have for a number of years been studying well-motivated models that involve multiple forms of matter also giving an excellent fit to the data, Guth says. Until now, however, the work has been limited to studying the early stages of the ending of inflation, where the math is relatively simple. The new work is based on a high-powered numerical lattice simulation which can probe much further into the complicated interactions at the end of inflation. The work shows more definitively than ever that a large class of models involving multiple forms of matter are in excellent agreement with observations.

The Least Understood Part of the Story

There are hundreds of proposals for producing the inflationary phase, but the transition between the inflationary phase and the so-called hot big bang is the least understood part of the story, says Richard Easther, professor of physics at the University of Auckland, who was not involved in the research. This paper breaks new ground by accurately simulating the postinflationary phase in models with many individual fields and complex kinetic terms. These are extremely challenging numerical simulations, and extend the state of the art for studies of nonlinear dynamics in the very early universe.

The Daily Galaxy, edited by Max Goldberg, via MIT News

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The Unbroken Story Birth of the Universe to the Big Bang & Beyond - The Daily Galaxy --Great Discoveries Channel

Credit: University of Nottingham

Researchers have developed a new theory for observing a quantum vacuum that could lead to new insights into the behavior of black holes.

The Unruh effect combines quantum physics and the theory of relativity. So far it has not been possible to measure or observe it, but now new research from a team led by the University of Nottingham has shed light on how this could be achieved using sound particles. The teams research has been published today in the journal Physical Review Letters.

The Unruh effect suggests that if you fly through a quantum vacuum with extreme acceleration, the vacuum no longer looks like a vacuum: rather, it looks like a warm bath full of particles. This phenomenon is closely related to the Hawking radiation from black holes.

A research team from the University of Nottinghams Black Hole Laboratory in collaboration with University of British Columbia and Vienna University of Technology has shown that instead of studying the empty space in which particles suddenly become visible when accelerating, you can create a two-dimensional cloud of ultra-cold atoms (Bose-Einstein condensate) in which sound particles, phonons, become audible to an accelerated observer in the silent phonon vacuum. The sound is not created by the detector, rather it is hearing what is there just because of the acceleration (a non-accelerated detector would still hear nothing).

One of the basic ideas of Albert Einsteins theory of relativity is: Measurement results can depend on the state of motion of the observer. How fast does a clock tick? How long is an object? What is the wavelength of a ray of light? There is no universal answer to this, the result is relative it depends on how fast the observer is moving. But what about the question of whether a certain area of space is empty or not? Shouldnt two observers at least agree on that?

No because what looks like a perfect vacuum to one observer can be a turbulent swarm of particles and radiation to the other. The Unruh effect, discovered in 1976 by William Unruh, says that for a strongly accelerated observer the vacuum has a temperature. This is due to so-called virtual particles, which are also responsible for other important effects, such as Hawking radiation, which causes black holes to evaporate.

To observe the Unruh effect directly, as William Unruh described it, is completely impossible for us today, explains Dr. Sebastian Erne who came from the University of Nottingham to the Atomic Institute of the Vienna University of Technology as an ESQ Fellow a few months ago. You would need a measuring device accelerated to almost the speed of light within a microsecond to see even a tiny Unruh-effect -we cant do that. However, there is another way to learn about this strange effect: using so-called quantum simulators.

Many laws of quantum physics are universal. They can be shown to occur in very different systems. One can use the same formulas to explain completely different quantum systems, says Jrg Schmiedmayer from the Vienna University of Technology. This means that you can often learn something important about a particular quantum system by studying a different quantum system.

Simulating one system with another has been especially useful for understanding black holes, since real black holes are effectively inaccessible, Dr. Cisco Gooding from the Black Hole laboratory emphasizes. In contrast, analog black holes can be readily produced right here in the lab.

This is also true for the Unruh effect: If the original version cannot be demonstrated for practical reasons, then another quantum system can be created and examined in order to see the effect there.

Just as a particle is a disturbance in empty space, there are disturbances in the cold Bose-Einstein condensate small irregularities (sound waves) that spread out in waves. As has now been shown, such irregularities should be detectable with special laser beams. Using special tricks, the Bose-Einstein condensate is minimally disturbed by the measurement, despite the interaction with the laser light.

Jrg Schmiedmayer explains: If you move the laser beam, so that the point of illumination moves over the Bose-Einstein condensate, that corresponds to the observer moving through the empty space. If you guide the laser beam in accelerated motion over the atomic cloud, then you should be able to detect disturbances that are not seen in the stationary case just like an accelerated observer in a vacuum would perceive a heat bath that is not there for the stationary observer.

Until now, the Unruh effect was an abstract idea, says Professor Silke Weinfurtner who leads the Black Hole laboratory at the University of Nottingham, Many had given up hope of experimental verification. The possibility of incorporating a particle detector in a quantum simulation will give us new insights into theoretical models that are otherwise not experimentally accessible.

Preliminary planning is already underway to carry out a version of the experiment using superfluid helium at the University of Nottingham. It is possible, but very time-consuming and there are technical hurdles for us to overcome, explains Jrg Schmiedmayer. But it would be a wonderful way to learn about an important effect that was previously thought to be practically unobservable.

Reference: Interferometric Unruh Detectors for Bose-Einstein Condensates by Cisco Gooding, Steffen Biermann, Sebastian Erne, Jorma Louko, William G. Unruh, Joerg Schmiedmayer and Silke Weinfurtner, 20 November 2020, Physical Review Letters.DOI: 10.1103/PhysRevLett.125.213603

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Combining Quantum Physics and the Theory of Relativity: Sound-Waves From a Quantum Vacuum at the Black Hole Laboratory - SciTechDaily

Visualization of quantum dots in bilayer graphene using scanning tunneling microscopy and spectroscopy reveals a three-fold symmetry. In this three-dimensional image, the peaks represent sites of high amplitude in the waveform of the trapped electrons. Credit: Zhehao Ge, Frederic Joucken, and Jairo Velasco Jr.

Researchers used a scanning tunneling microscope to visualize quantum dots in bilayer graphene, an important step toward quantum information technologies.

Trapping and controlling electrons in bilayer graphene quantum dots yields a promising platform for quantum information technologies. Researchers at UC Santa Cruz have now achieved the first direct visualization of quantum dots in bilayer graphene, revealing the shape of the quantum wave function of the trapped electrons.

The results, published on November 23, 2020, in Nano Letters, provide important fundamental knowledge needed to develop quantum information technologies based on bilayer graphene quantum dots.

There has been a lot of work to develop this system for quantum information science, but weve been missing an understanding of what the electrons look like in these quantum dots, said corresponding author Jairo Velasco Jr., assistant professor of physics at UC Santa Cruz.

While conventional digital technologies encode information in bits represented as either 0 or 1, a quantum bit, or qubit, can represent both states at the same time due to quantum superposition. In theory, technologies based on qubits will enable a massive increase in computing speed and capacity for certain types of calculations.

A variety of systems, based on materials ranging from diamond to gallium arsenide, are being explored as platforms for creating and manipulating qubits. Bilayer graphene (two layers of graphene, which is a two-dimensional arrangement of carbon atoms in a honeycomb lattice) is an attractive material because it is easy to produce and work with, and quantum dots in bilayer graphene have desirable properties.

These quantum dots are an emergent and promising platform for quantum information technology because of their suppressed spin decoherence, controllable quantum degrees of freedom, and tunability with external control voltages, Velasco said.

Understanding the nature of the quantum dot wave function in bilayer graphene is important because this basic property determines several relevant features for quantum information processing, such as the electron energy spectrum, the interactions between electrons, and the coupling of electrons to their environment.

Velascos team used a method he had developed previously to create quantum dots in monolayer graphene using a scanning tunneling microscope (STM). With the graphene resting on an insulating hexagonal boron nitride crystal, a large voltage applied with the STM tip creates charges in the boron nitride that serve to electrostatically confine electrons in the bilayer graphene.

The electric field creates a corral, like an invisible electric fence, that traps the electrons in the quantum dot, Velasco explained.

The researchers then used the scanning tunneling microscope to image the electronic states inside and outside of the corral. In contrast to theoretical predictions, the resulting images showed a broken rotational symmetry, with three peaks instead of the expected concentric rings.

We see circularly symmetric rings in monolayer graphene, but in bilayer graphene the quantum dot states have a three-fold symmetry, Velasco said. The peaks represent sites of high amplitude in the wave function. Electrons have a dual wave-particle nature, and we are visualizing the wave properties of the electron in the quantum dot.

This work provides crucial information, such as the energy spectrum of the electrons, needed to develop quantum devices based on this system. It is advancing the fundamental understanding of the system and its potential for quantum information technologies, Velasco said. Its a missing piece of the puzzle, and taken together with the work of others, I think were moving toward making this a useful system.

Reference: Visualization and Manipulation of Bilayer Graphene Quantum Dots with Broken Rotational Symmetry and Nontrivial Topology by Zhehao Ge, Frederic Joucken, Eberth Quezada, Diego R. da Costa, John Davenport, Brian Giraldo, Takashi Taniguchi, Kenji Watanabe, Nobuhiko P. Kobayashi, Tony Low and Jairo Velasco Jr., 23 November 2020, Nano Letters.DOI: 10.1021/acs.nanolett.0c03453

In addition to Velasco, the authors of the paper include co-first authors Zhehao Ge, Frederic Joucken, and Eberth Quezada-Lopez at UC Santa Cruz, along with coauthors at the Federal University of Ceara, Brazil, the National Institute for Materials Science in Japan, University of Minnesota, and UCSCs Baskin School of Engineering. This work was funded by the National Science Foundation and the Army Research Office.

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Direct Visualization of Quantum Dots Reveals Shape of Quantum Wave Function of the Trapped Electrons - SciTechDaily

The central unifying, overarching factor or cause is God himself.

Recently, I watched a fascinating NOVA episode entitled Einsteins Quantum Riddle. It was about advances in the area of quantum mechanics specifically, what is called quantum entanglement. Wikipedia has a long, complicated article about it. But the gist of it (which the TV special summarized for the layperson) is as follows:

Bottom line (beyond all the technical mumbo-jumbo of modern physics), is that even assuming that this phenomenon is true and a fact scientists have no explanation for how it could happen as it does. Its one of those things where the knowledge of science comes to an end: like the origin of life, the causes of the origins of the Big Bang, DNA and higher intelligence, and dark matter.

Einstein, as is well-known, had serious problems with quantum mechanics, with regard to its seemingly random and irrational nature, in relation to traditional notions of cause-and-effect. He famously stated, God doesnt play dice. Einsteins god was a pantheist one at best, but he was no atheist, and recognized that the universe had an unexplainable higher order and beauty of design that any thinking person couldnt deny. I have argued that this was a broad, bare-bones version of the classic theistic teleological (design) argument.

Science often gets to a place where it is completely baffled, but because it methodologically excludes God (which has essentially been the case since Darwin), and so often doesnt recognize its own inherent philosophical limitations (empiricism being only one form of knowledge among many), it rules out what is as plausible an explanation as anything else: God.

The most obvious example of this is Big Bang cosmology. This theory was formulated by a Catholic priest-scientist, Father Georges Lematre. It expressed in scientific detail what had already long since been present in the Bible: creatio ex nihilo (creation from nothing).

The theory of evolution runs into the same insuperable difficulties when it comes to describing exact sequences and causes for evolutionary change: especially across large gaps, such as the origins of life and DNA and of large classification groups to other ones. Its entirely possible as a method that God used to create (theistic evolution), but without the inclusion of God, science cannot explain many key aspects of it.

Intelligent design advocate and scientist Dr. Michael Behe believes that intelligent design doesnt necessarily require additional intervention by God after His initial act of creation.

All Christians, it seems to me, have to believe that (1) God created (Genesis, etc.), and (2) he in some sense sustains or upholds his creation.

Its a belief in a non-material or immaterial force or power or spirit, that profoundly influences the material universe and its creative processes, and which itself seems ultimately beyond purely scientific or empirical analysis.

In this view, of intelligent design and/or theistic evolution, God designed or foreordained that complex structures would evolve, and life and consciousness, etc., by some unknown non-material, overarching, guiding principle that transcends science, or concerning which science (presently) can give us no clues or answers.

He not only created scientific laws that work essentially on their own (hence can be observed and studied scientifically), but also supervises or ordains the entire project though not in an interventionist or supernatural/miraculous way. The processes and potentialities were there from the beginning, as a manifestation of his omnipotence and omniscience. Its just that some of them are supra-scientific.

I submit that the same explanation that suggests itself with regard to the Big Bang and the unexplained mysteries of evolutionary process: the creative and upholding/omnipotent power of God, is applicable and plausible also as the explanation of how quantum entanglement is possible at all. Here are biblical passages along these lines:

This is inspired revelation from God. God either does these things: establishes, preserves, holds together, allows to endure, and upholds all of his creation (which he brought into being from nothing) or he does not. Christians if they are consistent cannot disbelieve this. And Gods power is as plausible an explanation of quantum entanglement as anything else: if only methodologically atheist science will allow him to be discussed at all.

If scientists seek the vaunted unified theory in physics, its right in front of them: the central unifying, overarching factor or cause is God himself. The Bible has taught it these past 2000 or more years. Modern science keeps indirectly verifying it, in effect, by its inability to explain origins or (as in our present example) the basis and ultimate causes of experimentally verified quantum mechanics.

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Quantum Mechanics and the Upholding Power of God - National Catholic Register

The magic squares reflect the magic of mathematics. Magic Squares are square grids with a special arrangement of numbers in them. These numbers are special because every row, column, and diagonal adds up to the same number.

Recently, quantum physicist Gemma De las Cuevas and mathematicians Tim Netzer and Tom Drescher introduced the quantum magic square notion. For the first time, physicists studied the properties of this quantum version of magic squares in detail.

Tim Netzer and Tom Drescher from the Department of Mathematics and Gemma De las Cuevas from the Department of Theoretical Physics have introduced the quantum magic square, which is a magic square. Still, instead of numbers, one puts in matrices. This is a non-commutative, and thus quantum, a generalization of a magic square.

In the study, physicists show that quantum magic squares cannot be as quickly characterized as their classical cousins. More precisely, quantum magic squares are not convex combinations of quantum permutation matrices. Instead, they are richer and more complicated to understand.

Tom Drescher said,This is the general theme when generalizations to the non-commutative case are studied.

The work is at the intersection of algebraic geometry and quantum information and showcases the benefits of interdisciplinary collaboration.

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Physicists introduced the notion of the quantum magic square - Tech Explorist

Clifford Johnson spends his days dissecting some of sciences most inscrutable mysteries. How does quantum physics apply to our understanding of space and time? What is the true nature of black holes? What are the origins of the universe?

But, as the Marvel Cinematic Universe (MCU) ventures further into quantum realms, time travel and space exploration, Johnson has added to his daily musings. Hes become the MCUs go-to guy when its producers need to sprinkle a little scientific realism into their superhero stories.

With credits on television shows and films from Thor: Ragnarok and Avengers: Endgame to the forthcoming Ms. Marvel, Johnson has helped shape some of the MCUs most memorable depictions of science and scientists in action. With The Falcon and The Winter Soldier due for release on Disney+ this autumn, we spoke to the Los Angeles-based advisor about getting science right in the biggest movie franchise of all time.

Qualifications aside, how does one become Marvels go-to science advisor?

My involvement varies from project to project and Im by no means the only scientist they have on speed dial. The US National Academy of Science set up The Science and Entertainment Exchange to try and get better representation of science and scientists in entertainment media, and I came to the MCU through them. Marvel has been extremely smart in how they try to represent science. I call it Marvel science. Its obviously not real science, but it is rooted in things from the real world.

Is your involvement consistent from film to film?

It varies. The first thing I do is read the script and make copious notes and suggestions on every bit that I can. Sometimes they just want some scientific buzzwords, and to know what certain things might look like. In Thor: Ragnarok I was brought in to advise on wormholes. I suggested that each wormhole has a different character and visuals depending on what kind of astrophysical object we find at its end.

Whats the most direct impact youve had on the story?

Its fun when you get to work with the filmmakers from an early stage and can do a deep dive into the story. In that way, the science can get into the DNA of the storytelling. An example is in Agent Carter: they had this exotic material they wanted to use throughout the second series which I advised on based on knowledge of real life exotic materials. This was everything from containment of a substance you cant touch to how they might move this substance (I suggested magnetic fields) and designing machines which they actually built and used on set.

How detailed does it get? Do you sneak things in?

In season two of Agent Carter I filled the blackboards in Howard Starks lab with period-appropriate equations, modified slightly to relate to the problems they were trying to solve. Maybe me and one other person would appreciate whats in those equations, but it was fun.

As a huge comics fan, to what degree have you tried to influence the direction of the MCU?

As Agent Carter was about the early days of what would become SHIELD, I started suggesting to whoever would listen that this would be a good point to start building a reference framework that could be used for the future films, particularly with regards to the energy sources that later became the Infinity Stones. I offered to help them write the physics rules for them, so that they would be consistent from film to film, but no one got back to me. I think I was being a little bit optimistic about how much they wanted me to worry about that stuff!

Whats the most important thing to get right?

I want to give people the opportunity to recognise that everyone can be involved in science. In the comics, people like Tony Stark do science, meaning they can do anything in any scientific discipline. I wanted to change that because science is a collaborative field. In Infinity War they did a really good job of bringing in Shuri to help them save Vision (although I cant claim thats a result of my suggestion). Representation of people doing science in the MCU has evolved from just white men.

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This physicist keeps the science in Marvel's movies accurate (ish) - Wired.co.uk