Category Archives: Quantum Physics

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Art Hobson

FAYETTEVILLE, Ark. A paper recently published in the journal Quantum Engineering proposed a solution to a long-standing problem in quantum physics, popularly known as the Schrdinger's Cat problem. The paper, "Entanglement and the Measurement Problem," was authored by emeritus professor of physics, Art Hobson.

Schrdinger's Cat is a long-standing thought experiment used to explain the seemingly paradoxical state of quantum superposition, in which, for example, an atom is said to be both decaying and not decaying at the same time. The thought experiment begins when one imagines surrounding this atom with a measurement device that can detect an emitted particle.The device could, for instance, be a Geiger counter that will click when the particle hits it.According to quantum physics, this changes things. The atom is no longer said to be in a superposition of decaying and not decaying, but "entangled" with the detector.This entanglement appears to describe a detector that is both clicked and not clicked.

That said, physicists know that a large object like a Geiger counter cannot be in a superposition of clicking and not clicking. Erwin Schrdinger, one of the inventors of quantum physics, dramatized this by imagining that the detector is connected with a cat in such a way that, when the detector clicks, the cat dies. The cat effectively becomes the detector.Quantum physics then seems to imply that the atom plus cat entanglement describes a cat that is both dead and alive an example of the long-standing "measurement problem."

Hobson's paper examines entanglement by studying experiments conducted in 1990 at the purely microscopic level.In these experiments, two photons are entangled with each other. This entangled situation is identical mathematically with the atom plus detector entanglement, but the entirely microscopic nature of the two-photon system allows experimenters to manipulate the system in ways that would be impossible if one of the objects were a detector.

The implication of this, Hobson argues, is that entanglement is not what was previously thought, which was that the Schrdinger's cat entanglement predicted an undecayed nucleus and a live cat that are superposed with a decayed nucleus and a dead cat.He argues the experiments show that the theory predicts an undecayed nucleus that is correlated with a live cat, and a decayed nucleus that is correlated with a dead cat. Thus, the entangled state says the following:the nucleus is undecayed whenever the cat is alive, and the nucleus is decayed whenever the cat is dead. Hobson concludes that this solves the measurement problem.

Hobson retired in 1999 after 35 years of teaching. He has spent most of his time since retirement studying the foundations of quantum physics. He is a fellow of the American Physics Society. In 2006, he received the Robert A. Millikan Award, given by the American Association of Physics Teachers to members who have made notable and creative contributions to the teaching of physics. Since retirement, he has authored several research papers and a book on the foundations of quantum physics.

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Solution to Schrdinger's Cat Problem Proposed in New Paper - University of Arkansas Newswire

Every time you take a step, space itself glows with a soft warmth.

Called the FullingDaviesUnruh effect (or sometimes just Unruh effect if you're pushed for time), this eerie glow of radiation emerging from the vacuum is akin to the mysterious Hawking radiation that's thought to surround black holes.

Only in this case, it's the product of acceleration rather than gravity.

Can't feel it? There's a good reason for that. You'd need to move at an impossible speed to sense even the weakest of Unruh rays.

For now, the effect remains a purely theoretical phenomenon, far beyond our ability to measure. But that could soon change, following a discovery by researchers from the University of Waterloo in Canada and the Massachusetts Institute of Technology (MIT).

By going back to basics, they've demonstrated there could be a way to stimulate the Unruh effect so it can be studied directly under less extreme conditions.

In an unexpected twist, they might also have uncovered the secret to turning matter invisible.

The real prize, however, would be breaking new grounds in experiments that aim to unite two powerful but incompatible theories in physics one that describes how particles behave, the other covering the curving of space and time.

"The theory of general relativity and the theory of quantum mechanics are currently still somewhat at odds, but there has to be a unifying theory that describes how things function in the Universe," says mathematician Achim Kempf from the University of Waterloo.

"We've been looking for a way to unite these two big theories, and this work is helping to move us closer by opening up opportunities for testing new theories against experiments."

The Unruh effect sits right on the boundary of quantum laws and general relativity.

According to quantum physics, an atom sitting all alone in a vacuum would need to wait for an incoming photon to ripple through the electromagnetic field and give its electrons a jiggle before it could consider itself illuminated.

If we consider relativity, there is a way to cheat. Simply by accelerating, an atom could experience the smallest of wobbles in the surrounding electromagnetic field as low-energy photons, transformed by a kind of Doppler effect.

This interaction between the relative experience of waves in a quantum field and the jiggle of an atom's electrons relies on a shared timing in their frequencies. Any quantum effects that don't rely on timing are usually ignored, given on paper they tend to balance out in the long run.

Together with colleagues Vivishek Sudhir and Barbara Soda, Kempf showed that when an atom is accelerated, these usually negligible conditions become far more significant, and can actually take over as dominant effects.

By tickling an atom in just the right way, such as by using a powerful laser, they showed it's possible to make use of these alternative interactions to make moving atoms experience the Unruh effect without the need for large accelerations.

As a bonus, the team also found that given the right trajectory, an accelerating atom might turn transparent to incoming light, effectively suppressing its ability to absorb or emit certain photons.

Sci-fi applications aside, by identifying ways to influence an accelerating atom's ability to engage with ripples in a vacuum, it's possible we might be able to come up with new ways to find where quantum physics and general relativity give way to a new theoretical framework.

"For over 40 years, experiments have been hindered by an inability to explore the interface of quantum mechanics and gravity," says Sudhir, a physicist from MIT.

"We have here a viable option to explore this interface in a laboratory setting. If we can figure out some of these big questions, it could change everything."

This research was published in Physical Review Letters.

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Physicists Found a Way to Trigger The Strange Glow of Warp Speed Acceleration - ScienceAlert

A recent series of precise measurements of already known, standard particles and processes have threatened to shake up physics.

As a physicist working at the Large Hadron Collider (LHC) at CERN, one of the most frequent questions I am asked is When are you going to find something? Resisting the temptation to sarcastically reply Aside from the Higgs boson, which won the Nobel Prize, and a whole slew of new composite particles? I realize that the reason the question is posed so frequently is down to how we have depicted progress in particle physics to the wider world.

We often talk about progress in terms of discovering new particles, and this is frequently true. Studying a new, very heavy particle helps us see underlying physical processes often without annoying background noise. That makes it easy to explain the value of the discovery to the general public and politicians.

Recently, however, a series of precise measurements of ordinary already known, standard particles and processes have threatened to shake up physics. And with the LHC getting ready to run at higher energy and intensity than ever before, it is time to start discussing the implications widely.

The storage-ring magnet for the Muon G-2 experiment at Fermilab. Credit: Reidar Hahn, Fermilab

In truth, particle physics has always proceeded in two ways, of which new particles is one. The other is by making very precise measurements that test the predictions of theories and look for deviations from what is expected.

The early evidence for Einsteins theory of general relativity, for example, came from discovering small deviations in the apparent positions of stars and from the motion of Mercury in its orbit.

Particles obey a counter-intuitive but hugely successful theory called quantum mechanics. This theory shows that particles far too massive to be made directly in a lab collision can still influence what other particles do (through something called quantum fluctuations.) Measurements of such effects are very complex, however, and much harder to explain to the public.

But recent results hinting at unexplained new physics beyond the standard model are of this second type. Detailed studies from the LHCb experiment found that a particle known as a beauty quark (quarks make up the protons and neutrons in the atomic nucleus) decays (falls apart) into an electron much more often than into a muon the electrons heavier, but otherwise identical, sibling. According to the standard model, this shouldnt happen hinting that new particles or even forces of nature may influence the process.

The LHCb experiment at CERN. Credit: CERN

Intriguingly, though, measurements of similar processes involving top quarks from the ATLAS experiment at the LHC show this decay does happen at equal rates for electrons and muons.

Meanwhile, the Muon g-2 experiment at Fermilab in the US has recently made very precise studies of how muons wobble as their spin (a quantum property) interacts with surrounding magnetic fields. It found a small but significant deviation from some theoretical predictions again suggesting that unknown forces or particles may be at work.

The latest surprising result is a measurement of the mass of a fundamental particle called the W boson, which carries the weak nuclear force that governs radioactive decay. After many years of data taking and analysis, the experiment, also at Fermilab, suggests it is significantly heavier than theory predicts deviating by an amount that would not happen by chance in more than a million million experiments. Again, it may be that yet undiscovered particles are adding to its mass.

Interestingly, however, this also disagrees with some lower-precision measurements from the LHC (presented in this study and this one).

While we are not absolutely certain these effects require a novel explanation, the evidence seems to be growing that some new physics is needed.

Of course, there will be almost as many new mechanisms proposed to explain these observations as there are theorists. Many will look to various forms of supersymmetry. This is the idea that there are twice as many fundamental particles in the standard model than we thought, with each particle having a super partner. These may involve additional Higgs bosons (associated with the field that gives fundamental particles their mass).

Others will go beyond this, invoking less recently fashionable ideas such as technicolor, which would imply that there are additional forces of nature (in addition to gravity, electromagnetism and the weak and strong nuclear forces), and might mean that the Higgs boson is in fact a composite object made of other particles. Only experiments will reveal the truth of the matter which is good news for experimentalists.

The experimental teams behind the new findings are all well respected and have worked on the problems for a long time. That said, it is no disrespect to them to note that these measurements are extremely difficult to make. Whats more, predictions of the standard model usually require calculations where approximations have to be made. This means different theorists can predict slightly different masses and rates of decay depending on the assumptions and level of approximation made. So, it may be that when we do more accurate calculations, some of the new findings will fit with the standard model.

Equally, it may be the researchers are using subtly different interpretations and so finding inconsistent results. Comparing two experimental results requires careful checking that the same level of approximation has been used in both cases.

These are both examples of sources of systematic uncertainty, and while all concerned do their best to quantify them, there can be unforeseen complications that under- or over-estimate them.

None of this makes the current results any less interesting or important. What the results illustrate is that there are multiple pathways to a deeper understanding of the new physics, and they all need to be explored.

With the restart of the LHC, there are still prospects of new particles being made through rarer processes or found hidden under backgrounds that we have yet to unearth.

Written by Roger Jones, Professor of Physics, Head of Department, Lancaster University.

This article was first published in The Conversation.

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The Standard Model of Particle Physics May Be Broken A Physicist at the Large Hadron Collider Explains - SciTechDaily

The annals of science journalism werent always as inclusive as they could have been. SoPopSciis working to correct the record withIn Hindsight, a series profiling some of the figures whose contributions we missed. Read their stories and explore the rest of our 150th anniversary coveragehere.

In quantum physics, theres a law known as the conservation of parity, which is based on the notion that nature adheres to the ideal of symmetry. In a mirror-image of our world, it posits, the laws of physics would function the same waydespite everything being flipped. Since the early 1900s, experimental evidence suggested that this was true: To the pull of gravity or the draw of the electromagnetic force, the difference between left and right hardly mattered. So, physicists quite reasonably assumed that parity was a fundamental principle in the universe.

But in the 1950s, an experimental physicist at Columbia University named Chien-Shiung Wu devised an experiment that challengedand defiedthat law. Physics, she proved, to the astonishment of the field, did not always adhere to parity. Throughout her life, in fact, this woman demonstrated that parity was not the default; she flouted gender and racial barriers and eventually came to be known as the first lady of physics.

Wu was born in 1912 in a small fishing town north of Shanghai to parents who supported education for women. She displayed an extraordinary talent for physics as a college student in China. At the urging of Jing-Wei Gu, a female professor, she set her sights on earning a Ph.D. in the United States. In 1936, she arrived by ship in San Francisco and enrolled at the University of California, Berkeley, where she studied the nuclear fission of uranium.

She was 24 years old, in a new country where she wasnt fluent in the language and where the Chinese Exclusion Act, which prohibited Chinese workers from immigrating, was in full effect. It was preceded by the Page Act, which effectively banned the immigration of Chinese women based on the assumption that they intended to be sex workers. Wu was only able to enter the US because she was a student, but she was still ineligible for citizenship. There must have been so much tension and conflict there, says Leslie Hayes, vice president for education at the New York Historical Society. Im going to this place where I wont be welcome, but if I dont go, I wont be able to fulfill my goals and dreams.

After earning her Ph.D. in 1940, she married another Chinese-American physicist, and the couple moved to the East Coast in a long-shot search for tenure-track work. Major research institutes at the time were generally unwilling to hire women, people of color, or Jewish people, and the uptick in anti-Asian sentiment during World War II certainly didnt help. She was discriminated against as an Asian, but more so as a woman, Tsai-Chien Chiang wrote in his biography of Wu.

Nevertheless, shortly after a teaching stint at a womens college, she became the first female faculty member in Princeton Universitys physics department. That job was short lived; in 1944, Columbia University recruited her to work on the Manhattan Project, where she would advise a stumped Enrico Fermi on how to sustain a nuclear chain reaction.

Wu returned to research at Columbia after the war. Her reputation for brilliance and meticulousness grew in 1949 when she became the first to design an experiment that proved Fermis theory of beta decay, a type of radioactive decay in which a neutron spontaneously breaks down into a proton and a high-speed electron (a.k.a., a beta particle). In 1956, two theoretical physicists, Tsung-Dao Lee of Columbia and Chen Ning Yang of Princeton, sought Wus expertise in answering a provocative question: Is parity really conserved across the universe?

The law had been called into question by a problem known as theta-tau puzzle, a recently discovered paradox in particle physics. Theta and tau were two subatomic particles that were exactly the same in every respectexcept that one decayed into two smaller particles, and the other into three. This asymmetry confounded the physics community. Yang and Lee dove deep into the literature to see if anyone had ever actually proven that the nucleus of a particle always behaved symmetrically. As they found out, nobody had. So Wu, who they consulted during the process of writing their theoretical paper, got to work designing an experiment that would prove that it didnt.

Over the next few months, the men were in near constant communication with Wu. The monumental experiment that she designed and carried out rang the death knell for the concept of parity conservation in weak interactions, wrote nuclear physicist Noemie Benczer-Koller in her biography of Wu. Wus findings sparked such a sensation that they led to a Nobel Prize in physicsbut only for Yang and Lee. Wus groundbreaking work in proving the theory they advanced was ignored.

Though her genius allowed her to work in the same spaces as theoretical scientists, says Hayes, once there, she was not treated as a peer. But despite how frequently she experienced discrimination throughout her careerduring which she won every award in the field except the NobelWu didnt stop researching until her retirement in 1981.

Throughout her life, she was an outspoken advocate for the advancement of female physicistscampaigning, for the rest of her life, for the establishment of parity where it actually counted. Why didnt we encourage more women to go into science? she asked the crowd at an MIT symposium in 1964. I wonder whether the tiny atoms and nuclei, or the mathematical symbols, or the DNA molecules, have any preference for either masculine or feminine treatment.

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Chien-Shiung Wus work defied the laws of physics - Popular Science

New research explores the imaginative possibility that our reality is only one half of a pair of interacting worlds.

Physicists sometimes come up with bizarre stories that sound like science fiction. Yet some turn out to be true, like how the curvature of space and time described by Einstein was eventually confirmed by astronomical measurements. Others linger on as mere possibilities or mathematical curiosities.

In a new paper in Physical Review Research, Joint Quantum Institute (JQI) Fellow Victor Galitski and JQI graduate student Alireza Parhizkar investigated the imaginative possibility that our reality is only one half of a pair of interacting worlds. Their mathematical model may offer a fresh perspective for looking at fundamental aspects of realityincluding why our universe expands the way it does and how that relates to the most minuscule lengths allowed in quantum mechanics. These topics are critical to understanding our universe and are part of one of the great mysteries of modern physics.

The pair of scientists stumbled upon this new perspective when they were looking into something quite different, research on sheets of graphenesingle atomic layers of carbon in a repeating hexagonal pattern. They realized that experiments on the electrical properties of stacked sheets of graphene produced results that resembled little universes and that the underlying phenomenon might generalize to other areas of physics. In stacks of graphene, new electrical behaviors arise from interactions between the individual sheets, so maybe unique physics could similarly emerge from interacting layers elsewhereperhaps in cosmological theories about the entire universe.

A curved and stretched sheet of graphene laying over another curved sheet creates a new pattern that impacts how electricity moves through the sheets. A new model suggests that similar physics might emerge if two adjacent universes are able to interact. Credit: Alireza Parhizkar, JQI

We think this is an exciting and ambitious idea, says Galitski, who is also a Chesapeake Chair Professor of Theoretical Physics in the Department of Physics. In a sense, its almost suspicious that it works so well by naturally predicting fundamental features of our universe such as inflation and the Higgs particle as we described in a follow up preprint.

Stacked graphenes exceptional electrical properties and possible connection to our reality having a twin comes from the special physics produced by patterns called moir patterns. Moir patterns form when two repeating patternsanything from the hexagons of atoms in graphene sheets to the grids of window screensoverlap and one of the layers is twisted, offset, or stretched.

The patterns that emerge can repeat over lengths that are vast compared to the underlying patterns. In graphene stacks, the new patterns change the physics that plays out in the sheets, notably the electrons behaviors. In the special case called magic angle graphene, the moir pattern repeats over a length that is about 52 times longer than the pattern length of the individual sheets, and the energy level that governs the behaviors of the electrons drops precipitously, allowing new behaviors, including superconductivity.

Galitski and Parhizkar realized that the physics in two sheets of graphene could be reinterpreted as the physics of two two-dimensional universes where electrons occasionally hop between universes. This inspired the pair to generalize the math to apply to universes made of any number of dimensions, including our own four-dimensional one, and to explore if similar phenomenon resulting from moir patterns might pop up in other areas of physics. This started a line of inquiry that brought them face to face with one of the major problems in cosmology.

We discussed if we can observe moir physics when two real universes coalesce into one, Parhizkar says. What do you want to look for when youre asking this question? First you have to know the length scale of each universe.

A length scaleor a scale of a physical value generallydescribes what level of accuracy is relevant to whatever you are looking at. If youre approximating the size of an atom, then a ten-billionth of a meter matters, but that scale is useless if youre measuring a football field because it is on a different scale. Physics theories put fundamental limits on some of the smallest and largest scales that make sense in our equations.

The scale of the universe that concerned Galitski and Parhizkar is called the Planck length, and it defines the smallest length that is consistent with quantum physics. The Planck length is directly related to a constantcalled the cosmological constantthat is included in Einsteins field equations of general relativity. In the equations, the constant influences whether the universeoutside of gravitational influencestends to expand or contract.

This constant is fundamental to our universe. So to determine its value, scientists, in theory, just need to look at the universe, measure several details, like how fast galaxies are moving away from each other, plug everything into the equations and calculate what the constant must be.

This straightforward plan hits a problem because our universe contains both relativistic and quantum effects. The effect of quantum fluctuations across the vast vacuum of space should influence behaviors even at cosmological scales. But when scientists try to combine the relativistic understanding of the universe given to us by Einstein with theories about the quantum vacuum, they run into problems.

One of those problems is that whenever researchers attempt to use observations to approximate the cosmological constant, the value they calculate is much smaller than they would expect based on other parts of the theory. More importantly, the value jumps around dramatically depending on how much detail they include in the approximation instead of homing in on a consistent value. This lingering challenge is known as the cosmological constant problem, or sometimes the vacuum catastrophe.

This is the largestby far the largestinconsistency between measurement and what we can predict by theory, Parhizkar says. It means that something is wrong.

Since moir patterns can produce dramatic differences in scales, moir effects seemed like a natural lens to view the problem through. Galitski and Parhizkar created a mathematical model (which they call moir gravity) by taking two copies of Einsteins theory of how the universe changes over time and introducing extra terms in the math that let the two copies interact. Instead of looking at the scales of energy and length in graphene, they were looking at the cosmological constants and lengths in universes.

Galitski says that this idea arose spontaneously when they were working on a seemingly unrelated project that is funded by the John Templeton Foundation and is focused on studying hydrodynamic flows in graphene and other materials to simulate astrophysical phenomena.

Playing with their model, they showed that two interacting worlds with large cosmological constants could override the expected behavior from the individual cosmological constants. The interactions produce behaviors governed by a shared effective cosmological constant that is much smaller than the individual constants. The calculation for the effective cosmological constant circumvents the problem researchers have with the value of their approximations jumping around because over time the influences from the two universes in the model cancel each other out.

We dont claimeverthat this solves cosmological constant problem, Parhizkar says. Thats a very arrogant claim, to be honest. This is just a nice insight that if you have two universes with huge cosmological constantslike 120 orders of magnitude larger than what we observeand if you combine them, there is still a chance that you can get a very small effective cosmological constant out of them.

In preliminary follow up work, Galitski and Parhizkar have started to build upon this new perspective by diving into a more detailed model of a pair of interacting worldsthat they dub bi-worlds. Each of these worlds is a complete world on its own by our normal standards, and each is filled with matching sets of all matter and fields. Since the math allowed it, they also included fields that simultaneously lived in both worlds, which they dubbed amphibian fields.

The new model produced additional results the researchers find intriguing. As they put together the math, they found that part of the model looked like important fields that are part of reality. The more detailed model still suggests that two worlds could explain a small cosmological constant and provides details about how such a bi-world might imprint a distinct signature on the cosmic background radiationthe light that lingers from the earliest times in the universe.

This signature could possibly be seenor definitively not be seenin real world measurements. So future experiments could determine if this unique perspective inspired by graphene deserves more attention or is merely an interesting novelty in the physicists toy bin.

We havent explored all the effectsthats a hard thing to do, but the theory is falsifiable experimentally, which is a good thing, Parhizkar says. If its not falsified, then its very interesting because it solves the cosmological constant problem while describing many other important parts of physics. I personally dont have my hopes up for that I think it is actually too big to be true.

Reference: Strained bilayer graphene, emergent energy scales, and moir gravity by Alireza Parhizkar and Victor Galitski, 2 May 2022, Physical Review Research.DOI: 10.1103/PhysRevResearch.4.L022027

The research was supported by the Templeton Foundation and the Simons Foundation.

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Our Reality May Only Be Half of a Pair of Interacting Worlds - SciTechDaily

WATERLOO Cendikiawan Suryaatmadja of Indonesia is taking a break this summer before starting his PhD.

The 17-year-old is the third-youngest person in University of Waterloos history to graduate with a masters degree in physics, and he dreams about using the fundamental building blocks of the physical world to make it better.

I still have a long way to go, said Suryaatmadja during an interview at the Dana Porter Library on campus.

His research will focus on quantum information theory using quantum physics to manage the flow of information.

I think it is a very important field of physics, said Suryaatmadja. Its new, its emerging.

UW is a leading centre of research on quantum information theory, and the next generation of supercomputers that will use that research quantum computers.

You are essentially looking at things from the most fundamental and simplest level, and you just start to build a whole structure out of it, said Suryaatmadja.

After almost six years in Canada, Suryaatmadja is still not used to the changing weather and the need for so many clothes. He misses the warm, consistent weather of his home and the flavourful food of Indonesia.

Even a simple meal can have 12 to 14 spices, oh man, said Suryaatmadja. Im not saying the food in Canada is bad, but you guys use a lot of butter.

He also misses his family, and tries to speak with them every week. But he likes the diversity of Canada, especially around the UW campus.

You meet people with different ideas, different cultures, different perspectives, said Suryaatmadja. It really helps you think more critically, it really helps you get exposed to thoughts that are different from your own. I think Canada excels at that.

He grew up in Bogor, a city south of Jakarta on the Indonesian Island of Java. His first language is Indonesian, and Suryaatmadja taught himself English.

When Suryaatmadja started elementary school he was placed in Grade 3. After Grade 4 he studied on his own, and was recruited by UW when he was 12. Four years later he had completed a bachelors degree in mathematical physics with a minor in pure mathematics. It took more than a year to complete the masters and his PhD will also be done at UW.

Jeff Casello, UWs associate vice-president of graduate studies and post-doctoral affairs, calls Suryaatmadjas academic accomplishments remarkable.

Having the academic skills and personal drive to earn a masters degree at age 17 reflects a level of accomplishment that is incredibly rare, said Casello.

Suryaatmadja laughs at how it came about. He pressed the wrong button in the elevator at the institute in Bogor where he studied and prepared for math competitions. He walked off the elevator and into the arms of two UW recruiters Jean Lowry and Ken Seng Tan.

I just talked to them actually, said Suryaatmadja. This was before I graduated from high school.

At this point, he looks forward to a life of research that breaks new ground in physics and quantum information theory.

I just want to be a researcher. I dont know where. Lets see where things go. I still have a lot of time to make plans.

During the past six years hes joined many clubs on campus, and enjoys doing improv. He likes watching TV shows and movies that are comedies, or Sci-Fi blockbusters such as Dune and Blade Runner 2049. He enjoys Manga, DC Comics and books by Neil Gaiman, Terry Pratchett and graphic novels by Grant Morrison.

And I like walking a lot, especially in this weather, said Suryaatmadja.

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Whiz kid from Indonesia earns master's at University of Waterloo in physics at 17 - Waterloo Region Record

To our earliest human ancestors, the world was a bewildering place. From devastating natural disasters to the countless stars in the night sky, their universe was filled with phenomena that defied explanation.

As humans whose minds worked in just the same way as ours, they must have spent endless hours pondering their place within this mystifying world. They would have asked many of the same questions we continue to struggle with today: Who am I? What is my place in the universe? What is the nature of my sense of self?

To answer these questions, our ancestors filled their world with magic, monsters, and supernatural beings. They told stories about mythical creations that sparked a sense of wonder and mystery about the nature of the universe. Yet not so long ago on the timescale of human history, that all began to change.

Starting with the philosophers of the ancient world, humans began to question whether the natural forces that once seemed so far beyond our comprehension could be explained after all. Over the centuries, this movement grew into countless fields of scientific research.

As we began to uncover the fundamental building blocks of our universe, the need for magical forces to explain what we couldnt comprehend began to subside. Today, for example, the fields of quantum mechanics and general relativity tell us much about the nature of the matter that surrounds us, from subatomic to cosmological scales.

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Yet at the same time, ideas about the magical forces which instilled such wonder in our ancient ancestors still run deep in human culture. This natural sense of awe seems to have led to some unfortunate misconceptions about the brilliant minds who have contributed so much to our understanding of the universe.

Theres a notion that scientists have this sterile, clinical view of the world, that leaves no room for mystery, awe, or magic, Jim Al-Khalili, a theoretical physicist and author of The World According to Physics, told Big Think.

From stereotypes in fiction that frame scientists as brashly dismissive of any idea that seems slightly illogical, to groups who view science as an attack on their faith, these ideas remain popular today. But to Al-Khalili, they couldnt be further from the truth.

On the contrary, everything I learn about how the world is tells me its full of wonder, he told Big Think. The idea that Newton discovered that the invisible force pulling the apple down to the ground is exactly the same force keeping the Moon in orbit around the Earth is utterly profound and awe-inspiring.

To illustrate the wonder that pervades scientific research, Al-Khalili imagines the sum of human knowledge as an island.

The interior of the island is the well-established science we know very well; its shoreline is the limits of our understanding; and beyond it is the ocean of the unknown.

The shorelines of our island are constantly expanding outward. But just like the earliest seafarers, there is no way for us to know just how far the ocean surrounding extends, or if it even ends. For physicists like Al-Khalili, the ocean of the unknown is particularly vast.

So far, our knowledge of quantum mechanics has culminated in the Standard Model, which aims to describe the nature of the fundamental particles and forces that comprise our universe. The Standard Model can reliably explain the results of almost all experiments that physicists have thrown at it. But we know that these explanations are far from complete.

Among the Standard Models most glaring gaps is that it cant explain the nature of dark matter: the mysterious substance which astronomers claim must account for roughly 85% of all mass in the universe, but whose true nature continues to elude us, despite decades of efforts to detect it.

The Standard Model also cant explain dark energy, which is the cosmic-scale force thats thought to be driving the universes continuing expansion. Even further, physicists have yet to develop a single unifying theory that can simultaneously encompass the founding principles of quantum mechanics and general relativity.

As physicists delve deeper into these questions, theyre steadily realizing the extent of the discoveries theyve yet to make; the ocean surrounding our island of knowledge only appears to grow ever more vast.

As we expand the shorelines of our island, Al-Khalili thinks that the knowledge we have gained so far could turn out to be completely wrong, leading to completely new conceptions about the most basic building blocks of our universe.

One-hundred years from now, I may look back at the Jim of the early 21st century and think I was just as nave as the medieval scholars who thought the Sun orbited the Earth.

Yet physicists arent the only ones who perceive this expanding ocean. Ultimately, the fundamental phenomena they aim to explain can only go so far toward answering the questions first pondered by our distant ancestors about who we really are, and where we fit within the universe.

Despite millennia of scrutiny by billions of minds, our ocean of the unknown is only growing: a picture that is being repeated time and again across many fields of scientific research. In solving these mysteries, researchers from across the broad scope of modern science are increasingly realizing just how intertwined their fields really are.

Just as Newton first discovered the astonishing link between a falling apple and the orbiting Moon, extending our island further may involve finding links between phenomena we have previously thought of as unconnected. All the same, there is no guarantee that we will ever know how far the ocean surrounding us extends.

For Al-Khalili, if we look back at how far our scientific knowledge has come, and just how far we have yet to go, its impossible to claim that science is purely a cold, rational exercise.

We dont know if we will ever one day know everything about the nature of reality, and in a way, thats nice. Its frustrating but beautiful that we may never have all the answers.

Far from eliminating the sense of awe and wonder first felt by our distant ancestors, expanding our knowledge of science can only help it to grow. As Douglas Adams once put it, Id take the awe of understanding over the awe of ignorance any day.

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Jim Al-Khalili: How our ancient sense of wonder drives physics deeper into the unknown - Big Think

WEST LAFAYETTE, Ind. Black holes are everywhere right now at the middle of every galaxy, of course, as well as all over the news thanks to the recent picture taken of the black hole at the center of Earths own galaxy.

Matthew Lister, professor of physics and astronomy in the College of Science at Purdue University, explains the significance of the image, only the second one ever taken of a black hole. He was not part of the team that took the image, but as an expert on black hole phenomena, he is very excited about the development. The image is notable in that the addition of another radio telescope at the South Pole resulted in an improvement in resolution over the first picture of a black hole. The observations were challenging, due to the nature of the black hole itself.

The radio emission of the black hole at the center of our galaxy is quite weak, and the black hole environment varies quite rapidly, Lister said. Its like trying to take an image of a moving target where youre not getting a lot of light from it, so this required a lot of processing and comparison to computer models to be confident that the image reflects whats really going on at the galactic center.

An international cadre of scientists collaborated to piece together the final picture of the black hole. The images come from the Event Horizon Telescope, an array of telescopes across the globe that work together to study black holes, something Lister has done for more than 20 years. Lister ispart of the team that is designing the next-generation Event Horizon Telescope, which promises to image many more black hole systems in even sharper detail.

Lister and his collaborators recently discovered a supermassive black hole binary system, one of only two known such systems. The two black holes, which orbit each other, likely weigh 100 million suns each. The two are only between 200 astronomical units and 2,000 AU apart (one AU is the distance from the Earth to the sun), at least 10 times closer than the only other known supermassive binary black hole system.

Studying black holes is important for another, not quite as esoteric reason, too: Their extreme properties may offer an insight into the much-vaunted Theory of Everything or a unified field theory that would unite all observed physical laws of the universe.

We dont have a theory that connects gravity and quantum mechanics, Lister said. In the case of black holes, you have very large amounts of mass confined to a very, very small volume. In order to better understand how things like gravity and quantum mechanics are unified, black holes are a key subject to study.

About Purdue University

Purdue University is a top public research institution developing practical solutions to todays toughest challenges. Ranked in each of the last four years as one of the 10 Most Innovative universities in the United States by U.S. News & World Report, Purdue delivers world-changing research and out-of-this-world discovery. Committed to hands-on and online, real-world learning, Purdue offers a transformative education to all. Committed to affordability and accessibility, Purdue has frozen tuition and most fees at 2012-13 levels, enabling more students than ever to graduate debt-free. See how Purdue never stops in the persistent pursuit of the next giant leap athttps://stories.purdue.edu.

Media contact: Brittany Steff, bsteff@purdue.edu

Source: Matthew Lister, mlister@purdue.edu

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Painting a clearer picture of black holes - Purdue University

Alexander Gardner mailed his application to North Carolina A&T from what was likely a military prison cell somewhere in the US South. It was the mid-1950s; Gardner would have been in his late 20s. He had run away from home at the age of 14 to join the US Merchant Marines.

Gardner had been incarcerated for punching a commanding officer who called him a racial slur. He had only an 8th grade education, but North Carolina A&Ta university located in Greensboro, NCsaw his potential. They accepted him, and he graduated in 1958 with a degree in engineering physics. Five years later, Gardner became the first Black person to earn a physics PhD from the University of North Carolina at Chapel Hill. He returned to North Carolina A&T the year after that, this time as a member of the physics faculty.

Thats an unbelievable story, says Arlene Maclin, a former physics professor who credits Gardner as one of her earliest and most important mentors.

However, its far from the only extraordinary tale of triumph over adversity to come out of the Black physics community. And it was possible, in part, due to the unique support Gardner found at North Carolina A&T, which is classified as an HBCU, a Historically Black College or University.

HBCUs have played an important role in bringing Black students into physics. Prior to 2003, HBCUs consistently graduated the majority of Black physics-degree holders. In the year 2000, HBCUs enrolled just 13% of all Black postsecondary students but awarded a staggering 60% of physics degrees earned by Black students that year. Those numbers have been on a steady decline in the years since, but HBCUs still produce a disproportionate share of Black physics graduates today.

In 2020, there were 101 active HBCUs in the United States. Thirty of them offer a bachelors degree in physics, and 11 of those offer amasters degree in physics. Just four of themAlabama A&M University, Florida A&M University, Hampton University and Howard Universityoffer general physics PhD programs. HBCUs granted only an estimated 11 of the 1,910 physics PhDs awarded to US graduate students in 2018 and 2019.

Advocates for recruiting and retaining more Black students into physics often discuss how to balance support for Black students at HBCUs like North Carolina A&T, and at Primarily White Institutions like UNC Chapel Hill. But the Black physicists whove emerged from both HBCUs and PWIs suggest that the physics community should be more concerned about structural challenges that minority physics students face everywhere, and the toxic environments that can be found in any academic department.

A new initiative called TEAM-UP Together, aimed at doubling the number of African Americans earning undergraduate degrees in physics and astronomy by 2030, will work toward those goals.

Black students, especially Black women, are vastly underrepresented in physics. Despite making up 15.64% of the college-age population, Black students earned an average of 3% of bachelors degrees in physics between 2014 and 2018, according to the American Physical Society. The majority74.5%of those degrees went to Black men. During the same timeframe, Black students earned just 1.8% of doctoral degrees in physics.

Experts and alumni of HBCU physics programs agree that HBCUs succeed in attracting and retaining Black students because they can create a supportive environment for students from all walks of life, even the most disadvantaged.

HBCUs get the broadest breadth of the African American community, says Hakeem Oluseyi, president of the National Society of Black Physicists. Everybody gets the top. Everybody gets the middle class. But for those of us who are the real deep strugglerswho are just as brilliant, who are just as capable, and likely very much more hard-workingthe HBCUs are, in many ways, our bridge into that world, because they understand us from where we're coming from. Most of these other places dont.

Thomas Searles, an associate professor of electrical & computer engineering at the University of Illinois Chicago, agrees with Oluseyi. Searles earned his undergraduate degree at Morehouse College and served as an assistant professor of physics at Howard University, both HBCUs. HBCUs are about mentoring all students, not just the best and the brightesteverybody, he says.

Still, HBCUs are not exempt from issues related to bias and discrimination.

Ive experienced more sexism at HBCUs than I experienced in other places that I've worked, and I've worked at the NSF, the CIA, MIT Lincoln Lab, Oak Ridge, Maclin says. As a Black woman, I was prepared to deal with racism, but not sexism.

More women than men have enrolled at HBCUs in every year since 1976. But Maclin explains that even at HBCUs, Black women in faculty must work harder to gain tenure and secure administrative support for their initiatives. The most recent data reported by the National Center for Education Statistics for the fall of 2001 found that Black women represented 27% of all full-time instructional and research faculty and 17% of full professors at HBCUswith Black men making up 31% and 36% of those roles, respectively. Maclin suggests that HBCU physics students who are women likely face similar difficulties.

Black women still do not have a critical mass in physics, anywhere, Maclin says. We dont have five Black women physicists anywhere working together. Nowhere.

Maclin says she once offered to help the chair of an HBCU physics department recruit more Black women. He never took me up on that challenge, she says.

Tennille Presley, an associate professor of physics at Winston-Salem State University, an HBCU in North Carolina, says she has similarly noted a disconnect between the gender breakdown of students and professors at HBCUs.

I agree with Dr. Maclin, Presley says. "In general, there should be more diversity in physics departments, especially as it relates to the inclusion of Black women and other women of colorand that includes both students and faculty."

Of course, Black women in PWI physics departments also face challenges that their Black male peers do not. The same is true for Black physics students who may be LGBTQIA+, disabled, foreign-born, or who hold any other marginalized identity in addition to being Black.

Certain identities are seen as conflicting [with our ideas of] who a scientist is, and who a physicist is, says Farrah Simpson, a doctoral candidate in physics who earned her undergraduate degree at Columbia University, and who also serves as student representative on the National Society of Black Physicists executive board.

Being Black, queer and a womanall these intersectional identitiesa lot of the time I feel within scientific spaces that people expect you to behave a certain way, or to have a certain identity, and your identity is [seen] as contradicting that, she says.

Maintaining a doctoral degree program in physics requires resources that historically and chronically underfunded HBCUs may be unable or unwilling to provide.

Physics departments are not cheap to maintain for the university, says Claudia Rankins, former dean of the School of Science at Hampton University. "Many small physics departments only graduate a few students every year, yet the professors who teach the upper-level courses, as well as the labs, need to be there.[It's] the same struggle other small programs or majors encounter."

Recruiting and retaining faculty is also a challenge for cash-strapped HBCU programs, where faculty made an average of $24,000 less per year than their PWI counterparts in 2019-2020.

So, the majority of physics doctoral degreesmore than 99%, according to the AIPare awarded by PWIs.

Institutions have partnered via bridge programs, which are specifically designed to help students transition from undergraduate and/or masters degrees at an HBCU to a doctoral degree at a PWI. These programs aim to provide mentoring that students moving to an institution where they are in the minority may need and may not receive. However, HBCU faculty and bridge program alumni often criticize these programs for failing to deliver adequate support to the students who participate. In part, the issue comes down to a lack of emphasis on mentoring at PWIs, especially the most elite.

Ive heard from professors at MIT who have said, Well, HBCUs are smaller; they have fewer students. They can afford to really mentor students in a proper way. At a place like MIT, we dont have that luxury, says Dara Norman, deputy director for the Community Science and Data Center at NSF's National Optical-Infrared Astronomy Research Laboratory.

Norman says this attitude is common among faculty at R1 universities. But Norman, who took nearly all of MITs core physics classes as part of her undergraduate degree, also says that mentorship is crucial for students who may not know what to expect when arriving on university campuses.

My parents did not go to college in the regular way; both my parents were in the Navy, Norman says. When I got to college, I realized I didnt really know what college wasAnd I couldnt fall back on my parents experienceI wonderif I had hit the ground running, would I have been in better shape?

PWI physics departments can also create environments that are actively hostile toward Black students.

Charles Brown, a postdoctoral researcher in quantum simulation at the University of California, Berkeley, can detail numerous instances of racialized microaggressions and even open hostility during his time as a graduate student in the physics department at Yale University. In a 2020 Physics Today article, Brown recounted stories of strangers handing him trash as though he were a member of the cleaning staff; of being denied entry to buildings while streams of non-black people passed by without showing ID; of being constantly asked whether he was affiliated with Yale at all.

It puts cracks in the foundation of your identity in the field, of your sense of belonging to the field, Brown says. Being a student is hard. Youre learning lots of difficult stuff. Youre navigating some new environment. And when youre getting constant messages that you don't belong, and that you're not respected, it makes it that much harder to do the thing thats already hard for students of any background.

Different students deal with these encounters in different ways, but however Black students may process these incidents, they do add up, says Falcon Rankins, head of PRISSEM Academic Services, an organization that works to support Black HBCU STEM faculty.

[There is so much] labor that Black students, female students have to do in terms of that calculus around, you know: Is this racism? Rankins says. Is this person being sexist? Is this person assuming that I dont know how to do something because Im Black? All those questions that we have to ask ourselvesI think thats real labor that isnt always appreciated as labor.

Ultimately, providing students with a welcoming environment is crucial to retaining those students at any educational institution. We keep [pursuing] these pipeline-building efforts without asking, Where does this pipeline dump out at the end of the day? Rankins says, noting that this applies to the entirety of the physics ecosystem and STEM fields as a whole.

[Physics] departments need to take a really close, deep-dive, data-driven look at what's going on in their particular context, and fix that, says Arlene Modeste Knowles, who serves as project manager for the American Institute of Physics National Task Force to Elevate African American Representation in Undergraduate Physics & Astronomy (TEAM-UP). Because if you recruit students into a toxic environment, it's going to be a revolving door. Those students aren't going to make it through.

In 2020, the AIP published an example of exactly the kind of data-driven work Knowles is talking about with The Time is Now, a detailed report based on the organizations two-year study examining the underrepresentation of Black students in undergraduate physics departments.

In April, the TEAM-UP diversity task force was awarded a $12.5 million, five-year grant by the Simons Foundation and Simons Foundation International to launch TEAM-UP Together, a collective action aimed at helping the task force achieve its goal of doubling the number of African-Americans earning undergraduate degrees in physics and astronomy by 2030.

The grant will initially support scholarships for students studying physics and astronomy at HBCUs and other predominantly Black institutions, before eventually extending to students at all undergraduate institutions in the US. The funding will also support undergraduate departments that have committed to implementing recommendations set out by the 2020 TEAM-UP report.

I don't want to see any other African American students endure harm in a physics or astronomy department, Knowles says.I want to see them thrive in those environments. With TEAM-UP Together, which will support the physical science community and leverage the enormous influence of AAS, APS, AAPT, SPS and AIP to catalyze systemic change, we have a chance at making this a reality.

While there is no surefire solution to these problems, Presley suggests that the physics community would do well to fall back on the tool it knows best: Educate others, Presley says. I think the more that [these issues] are brought to the forefront, the better things can be.

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The other physics problem | symmetry magazine - Symmetry magazine

By Harvard John A. Paulson School of Engineering and Applied SciencesMay 3, 2022

An illustration of a near-zero index metamaterial shows that when light travels through, it moves in a constant phase. Credit: Second Bay Studios/Harvard SEAS

Zero-index metamaterials offer new insights into the foundations of quantum mechanics.

In physics, as in life, its always good to look at things from different perspectives.

Since the dawn of quantum physics, how light moves and interacts with matter around it has been primarily described and understood mathematically through the lens of its energy. Max Planck used energy to explain how light is emitted by heated objects in 1900, a seminal study in the foundation of quantum mechanics. Albert Einstein used energy when he introduced the concept of the photon in 1905.

But light has another, equally important quality known as momentum. And, as it turns out, when you take momentum away, light starts behaving in really interesting ways.

An international team of physicists is re-examining the foundations of quantum physics from the perspective of momentum and exploring what happens when the momentum of light is reduced to zero. The researchers are led by Michal Lobet, a research associate at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and Eric Mazur, the Balkanski Professor of Physics and Applied Physics at SEAS,

The research was published in the journal Nature Light Science & Applications on April 25, 2022.

Any object with mass and velocity has momentum from atoms to bullets to asteroids and momentum can be transferred from one object to another. A gun recoils when a bullet is fired because the momentum of the bullet is transferred to the gun. At the microscopic scale, an atom recoils when it emits light because of the acquired momentum of the photon. Atomic recoil, first described by Einstein when he was writing the quantum theory of radiation, is a fundamental phenomenon that governs light emission.

But a century after Planck and Einstein, a new class of metamaterials is raising questions regarding these fundamental phenomena. These metamaterials have a refractive index close to zero, meaning that when light travels through them, it doesnt travel like a wave in phases of crests and troughs. Instead, the wave is stretched out to infinity, creating a constant phase. When that happens, many of the typical processes of quantum mechanics disappear, including atomic recoil.

Why? It all goes back to momentum. In these so-called near-zero index materials, the wave momentum of light becomes zero and when the wave momentum is zero, odd things happen.

As physicists, its a dream to follow in the footsteps of giants like Einstein and push their ideas further. We hope that we can provide a new tool that physicists can use and a new perspective, which might help us understand these fundamental processes and develop new applications.

Michal Lobet, Research Associate, SEAS

Fundamental radiative processes are inhibited in three dimensional near-zero index materials, says Lobet, who is currently a lecturer at the University of Namur in Belgium. We realized that the momentum recoil of an atom is forbidden in near-zero index materials and that no momentum transfer is allowed between the electromagnetic field and the atom.

If breaking one of Einsteins rules wasnt enough, the researchers also broke perhaps the most well-known experiment in quantum physics Youngs double-slit experiment. This experiment is used in classrooms across the globe to demonstrate the particle-wave duality in quantum physics showing that light can display characteristics of both waves and particles.

In a typical material, light passing through two slits produces two coherent sources of waves that interfere to form a bright spot in the center of the screen with a pattern of light and dark fringes on either side, known as diffraction fringes.

In the double slit experiment, light passing through two slits produces two coherent sources of waves that interfere to form a bright spot in the center of the screen with a pattern of light and dark fringes on either side, known as diffraction fringes. Credit: Harvard John A. Paulson School of Engineering and Applied Sciences

When we modeled and numerically computed Youngs double-slit experiment, it turned out that the diffraction fringes vanished when the refractive index was lowered, said co-author Larissa Vertchenko, of the Technical University of Denmark.

As it can be seen, this work interrogates fundamental laws of quantum mechanics and probes the limits of wave-corpuscle duality, said co-author Iigo Liberal, of the Public University of Navarre in Pamplona, Spain.

While some fundamental processes are inhibited in near-zero refractive index materials, others are enhanced. Take another famous quantum phenomenon Heisenbergs uncertainty principle, more accurately known in physics as the Heisenberg inequality. This principle states that you cannot know both the position and speed of a particle with perfect accuracy and the more you know about one, the less you know about the other. But, in near-zero index materials, you know with 100% certainty that the momentum of a particle is zero, which means you have absolutely no idea where in the material the particle is at any given moment.

This material would make a really poor microscope, but it does enable to cloak objects quite perfectly, Lobet said. In some way, objects become invisible.

These new theoretical results shed new light on near-zero refractive index photonics from a momentum perspective, said Mazur. It provides insights into the understanding of light-matter interactions in systems with a low- refraction index, which can be useful for lasing and quantum optics applications.

The research could also shed light on other applications, including quantum computing, light sources that emit a single photon at a time, the lossless propagation of light through a waveguide, and more.

The team next aims to revisit other foundational quantum experiments in these materials from a momentum perspective. After all, even though Einstein didnt predict near-zero refractive index materials, he did stress the importance of momentum. In his seminal 1916 paper on fundamental radiative processes, Einstein insisted that, from a theoretical point of view, energy and momentum should be considered on a completely equal footing since energy and momentum are linked in the closest possible way.

As physicists, its a dream to follow in the footsteps of giants like Einstein and push their ideas further, said Lobet. We hope that we can provide a new tool that physicists can use and a new perspective, which might help us understand these fundamental processes and develop new applications.

Reference: Momentum considerations inside near-zero index materials by Michal Lobet, Iigo Liberal, Larissa Vertchenko, Andrei V. Lavrinenko, Nader Engheta and Eric Mazur, 25 April 2022, Light: Science & Applications.DOI: 10.1038/s41377-022-00790-z

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In Einsteins Footsteps and Beyond: New Insights Into the Foundations of Quantum Mechanics - SciTechDaily