Category Archives: Quantum Physics
String theory used to describe the expanding universe – Advanced Science News
We know that the universe is expanding, and our understanding of nature based on general relativity and the Standard Model of elementary particles is consistent with this observation. However, these theories of particles and their interactions break down when we try to apply them to the physical phenomena that occurred in the first moments following the Big Bang preventing us from reaching a complete understanding of the evolution of the universe.
Our theories fail because the temperature and density of matter just after the Big Bang were so high that a concept called quantum gravity is required to describe the physical processes that took place. The problem is that this theory requires a unification of general relativity and quantum mechanics. Though this has not yet been fully understood, there are some viable candidates for a theory of quantum gravity, such as string theory.
To address the problem of unknown quantum gravitational effects in the early universe, a team of theoretical physicists from Japan applied a string theory-inspired technique known as holographic duality. This allowed them to perform calculations using familiar methods of elementary particle physics rather than an impossibly complex computation usually required in quantum gravity applications.
The most difficult problem one encounters on the way to finding a correct theory of quantum gravity is a lack of experimental data. Fundamental interactions are usually studied with elementary particle accelerators, which smash together beams of particles moving at velocities close to the speed of light. From the velocities of the particles born in these collisions and the angles at which they leave, scientists can extract valuable information about their fundamental interactions.
The key issue here is that the gravitational effects in most elementary particle interactions are negligible (though not under the extreme conditions in the early universe!), and they cannot be measured using modern accelerators. For example, the gravitational attraction between two electrons is more than 42 orders of magnitude weaker than the electromagnetic repulsion between them. Because of this, studies of quantum gravity have so far been only theoretical.
For decades, the most promising approach to quantum gravity has been string theory, the main postulate of which is that elementary particles are not point-like, but are tiny, oscillating strings. Unique vibrational modes of these strings gives rise to a different elementary particle, such as electrons, quarks, and yet-to-be observed gravitons, which should mediate gravitational interactions similar to how photons mediate electromagnetic interactions.
Unfortunately, our current understanding of string theory is incomplete and doesnt allow us to study many quantum gravitational effects quantitatively.
Although string theory has not yet reached its full potential, research in this area has led to the development of many theoretical tools that can be used outside of it. The most radical and powerful, although not fully proven, is known as holographic duality or correspondence.
The holographic hypothesis claims that events inside a region of space that involve quantum gravity and are described by string theory can also be described by a gravity-free quantum theory defined on the surface of that region. The latter theory is sufficiently easier to deal with, and we have learned much about theories of this type by studying electromagnetic, weak, and strong interactions.
The existence of this duality means that for every measurable quantity in quantum gravitational theory there must be an analogue in the gravity-free alternative. The validity of holographic duality has been verified by hundreds of research papers through direct calculations of various quantities on both sides of the duality.
Since 1997, when the first version of holographic correspondence was proposed by Juan Maldacena, many more pairs of theories connected by this equivalence have been discovered and analyzed, but the rule that a higher-dimensional space includes gravity and a lower-dimensional one does not always remains satisfied.
Some of these theories of quantum gravity are known to be related to string theory, whereas the connection between the rest with strings has not yet been uncovered but is usually believed to exist.
An unfortunate feature of the holographic approach in studying quantum gravity in the real world is that in most known examples of the duality, the higher-dimensional theory mathematically describes quantum gravity in what is called anti-de Sitter space, which doesnt look like our expanding universe, and whose geometry corresponds to what mathematicians call de Sitter space.
The remarkable achievement of the new study is that the authors were able to find a non-gravitational theory equivalent to quantum gravity in a universe that is quite similar to our own. The most important difference is that it has only three dimensions two spatial directions and one time unlike our own universe, which is four-dimensional (three space dimensions and one time dimension).
Gravity in three dimensions is much simpler than in four, said Tadashi Takayanagi, a professor at the Yukawa Institute for Theoretical Physics and one of the authors of the study. However, we believe the basic mechanism of how the holography works in de Sitter space should not depend on the dimension.
The new theory is proposed as an equivalent to quantum gravity in a lower-dimensional expanding universe defined in one spatial and one temporal dimension, known as the Wess-Zumino-Witten model.
Although the three-dimensional universe they deal with is not exactly like ours, the authors think that their work is an important step towards understanding quantum gravity in the real world.
Since we do not know at all the basic mechanisms of how the holography in de Sitter spaces works, it is useful to start with constructing the most simple example, as we did in this work, said Takayanagi. At the same time, this helps us to verify whether a holographic duality exists for de Sitter spaces or not. Moreover, in our simple mode, we can take into account quantum corrections [to general relativity].
As is usual in this branch of theoretical physics, the scientists havent proven the duality because to do so, they would have to compute all possible physical quantities on both sides of the correspondence and compare the results. Instead, they computed some, and found an exact match from which they concluded that their guess was correct.
Most of the authors calculations ignored quantum effects on the gravitational side of duality and taking them into account will be the course of future work. If the scientists are successful in this, they plan to generalize their results and apply them to our four-dimensional universe.
If we can understand this question from our three-dimensional example, we hopewe can generalize the results to higher dimensions and finally challenge theproblem of explaining the emergence of our four-dimensional universe, concluded Takayanagi.
Reference: Yasuaki Hikida, et al., CFT duals of three-dimensional de Sitter gravity, Journal of High Energy Physics, (2022). DOI: 10.1007/JHEP05(2022)129
Image Credit: Johnson Martin Pixabay
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String theory used to describe the expanding universe - Advanced Science News
We exist. What can that fact teach us about the Universe? – Big Think
For thousands of years, humans have pondered the meaning of our existence. From philosophers who debated whether their minds could be trusted to provide accurate interpretations of our reality to physicists whove attempted to interpret the weirder aspects of quantum physics and relativity, weve learned that some aspects of our Universe appear to be objectively true for everyone, while others are dependent on the actions and properties of the observer.
Although the scientific process, combined with our experiments and observations, have uncovered many of the fundamental physical laws and entities that govern our Universe, theres still much that remains unknown. However, just as Descartes was able to reason, I think, therefore I am, the fact of our existence the fact that we are has inevitable physical consequences for the Universe as well. Heres what the simple fact that we exist can teach us about the nature of our reality.
The gravitational behavior of the Earth around the Sun is not due to an invisible gravitational pull, but is better described by the Earth falling freely through curved space dominated by the Sun. The shortest distance between two points isnt a straight line, but rather a geodesic: a curved line thats defined by the gravitational deformation of spacetime. The laws of the Universe allow for, but do not mandate, the existence of intelligent observers.
To start with, the Universe has a set of governing rules, and weve been able to make some sense of at least some of them. We understand how gravity works at a continuous, non-quantum level: by matter and energy curving spacetime and by that curved spacetime dictating how matter and energy move through it. We know a large portion of the particles that exist (from the Standard Model) and how they interact through the three other fundamental forces, including at the quantum level. And we know that we exist, composed of those very same particles and obeying those same laws of nature.
Based on those facts, physicistBrandon Carterformulated two statements back in 1973 that seem like they must be true:
These two statements are known, today, as theWeak Anthropic Principle and the Strong Anthropic Principle, respectively. When used properly, they can enable us to draw incredibly powerful conclusions and constraints about what our Universe is like.
This chart of the particles and interactions detail how the particle of the Standard Model interact according to the three fundamental forces that Quantum Field Theory describes. When gravity is added into the mix, we obtain the observable Universe that we see, with the laws, parameters, and constants that we know of governing it. Mysteries, such as dark matter and dark energy, still remain.
Think about these facts, all together. The Universe has parameters, constants, and laws that govern it. We exist within this Universe. Therefore, the sum total of everything that determines how the Universe works must allow for creatures like us to come into existence within it.
Travel the Universe with astrophysicist Ethan Siegel. Subscribers will get the newsletter every Saturday. All aboard!
This seems like a set of simple, self-evident facts. If the Universe were such that it was physically impossible for creatures like us to exist, then we would never have come into existence. If the Universe had properties that were incompatible with any form of intelligent life existing, then no observers like us could have come into existence.
But we are here. We exist. And therefore, our Universe does exist with such properties that an intelligent observer could have possibly evolved within it. The fact that we are here and that we actively engage in the act of observing the Universe implies this: the Universe is wired in such a way that our existence is possible.
That is the essence of the Anthropic Principle in general.
This long-exposure image captures a number of bright stars, star-forming regions, and the plane of the Milky Way above the southern hemispheres ALMA observatory. This is literally one of the most powerful ways we have of being observers in the Universe, and yet its not clear what role, if any, being an intelligent observer has on affecting the Universe itself.
It doesnt seem like this statement should be controversial. It also doesnt seem like it teaches us very much, at least on the surface. But if we start to look at a variety of physical puzzles that the Universe has presented to us over the years, we start to see just how powerful an idea it can be for scientific discovery.
The fact that we are observers made of atoms and that many of those atoms are carbon atoms tells us that the Universe must have created carbon in some fashion. The light elements, like hydrogen, helium, and their various isotopes, were formed in the early stages of the Big Bang. The heavier elements are formed in stars of various types throughout their lives.
But in order to form those heavier elements, there must be some way to form carbon: the sixth element in the periodic table. Carbon, in its most common form, has 6 protons and 6 neutrons in its nucleus. If its formed in stars, there must be some way to form it from the other elements that already exist in stars: elements like hydrogen and helium. Unfortunately, the numbers didnt work out.
This cutaway showcases the various regions of the surface and interior of the Sun, including the core, which is the only location where nuclear fusion occurs. As time goes on, the helium-rich core will contract and heat up, enabling the fusion of helium into carbon. However, additional nuclear states for a carbon-12 nucleus beyond the ground state is required for the necessary reactions to occur.
We know the mass of carbon-12, and the masses of the helium and hydrogen nuclei that are so abundant in the stars. The easiest way to get there would be to take three independent helium-4 nuclei and fuse them all together simultaneously. Helium-4 has two protons and two neutrons in its nucleus, so its easy to imagine that fusing three of them together would give you carbon-12, and hence could create the carbon we need in our Universe.
But three helium nuclei, combined, are too massive to efficiently produce carbon-12. When two helium-4 nuclei fuse together, they produce beryllium-8 for just ~10-16s, before it decays back to two helium nuclei. Although occasionally a third helium-4 nucleus could get in there if the temperatures are high enough, the energies are all wrong for producing carbon-12; theres too much energy. The reaction just wouldnt give us enough of the carbon our Universe needs.
Fortunately, physicist Fred Hoyle understood how the anthropic principle worked, and realized that the Universe needed a pathway to make carbon from helium. He theorized that if there were an excited state of the carbon-12 nucleus, at a higher energy that was closer to the rest mass of three helium-4 nuclei combined, the reaction could occur. This nuclear state, known asthe Hoyle State, was discovered just five years later by nuclear physicist Willie Fowler, who also discovered thetriple-alpha processthat formed it, just as Hoyle predicted.
The prediction of the Hoyle State and the discovery of the triple-alpha process is perhaps the most stunningly successful use of anthropic reasoning in scientific history. This process is what explains the creation of the majority of carbon thats found in our modern-day Universe.
Another time the anthropic principle was successfully applied was to the puzzle of understanding what the vacuum energy of the Universe is. In quantum field theory, you can try to calculate what the energy of empty space is: known as the zero-point energy of space. If you were to remove all the particles and external fields from a region of space no masses, no charges, no light, no radiation, no gravitational waves, no curved spacetime, etc. youd be left with empty space.
But that empty space would still contain the laws of physics in them, which means that it would still contain the fluctuating quantum fields that exist everywhere throughout the Universe. If we try and calculate what the energy density of that empty space is, we get an absurd value thats far too high: so large that it would cause the Universe to have recollapsed just a tiny fraction of a second after the Big Bang. Clearly, the answer we get from doing that calculation is wrong.
Even in the vacuum of empty space, devoid of masses, charges, curved space, and any external fields, the laws of nature and the quantum fields underlying them still exist. If you calculate the lowest-energy state, you may find that it is not exactly zero; the zero-point (or vacuum) energy of the Universe appears to be positive and finite, although small.
So whats the right value, then? Although we still dont know how to calculate it, today, physicist Stephen Weinberg calculated an upper limit on what it could possibly be back in 1987, making astonishing use of the anthropic principle. The energy of empty space determines how quickly the Universe expands or contracts, even apart from all the matter and radiation within it. If that expansion (or contraction) rate is too high, we could never form life, planets, stars, or even molecules and atoms within the Universe.
If we use the fact that our Universe has galaxies, stars, planets, and even human beings on one of them, we can place extraordinary limits on how much vacuum energy could possibly be in the Universe. Weinbergs 1987 calculation demonstrated that it must be at least 118 orders of magnitude that is, a factor of 10118 smaller than the value obtained from quantum field theory calculations.
When dark energy was empirically discovered in 1998, we got to measure that number for the first time: it was 120 orders of magnitude (a factor of 10120) smaller than the nave prediction. Even without the necessary tools to perform the calculations needed to obtain the answer, the anthropic principle got us remarkably close.
The string landscape might be a fascinating idea thats full of theoretical potential, but it cannot explain why the value of such a finely-tuned parameter like the cosmological constant, the initial expansion rate, or the total energy density have the values that they do. Still, understanding why this value takes on the particular one it does is a fine-tuning question that most scientists assume has a physically-motivated answer.
Just two years ago, in 2020, theoretical physicistJohn Barrowdied, a victim of colon cancer. Back in 1986, he cowrote a prominent book with Frank Tipler,The Anthropic Cosmological Principle. In that book, they redefined the anthropic principle as the following two statements:
Although these statements might seem equivalent on the surface to the prior ones, they add up to something very different. Instead of contending, as Carter originally did, that Our existence, as observers, means that the Universes laws must allow observers to possibly exist, we now have The Universe must allow carbon-based, intelligent life, and that hypothetical Universes where that life does not develop are not permitted.
The existence of complex, carbon-based molecules in star forming regions is interesting, but isnt anthropically demanded. Here, glycoaldehydes, an example of simple sugars, are illustrated in a location corresponding to where they were detected in an interstellar gas cloud.
This highly influential (and controversial) reframing of the anthropic principle takes us from demanding that the Universe must not make it impossible for observers to exist, because we do, to mandating that a Universe where intelligent observers do not arise cannot be allowed. If that sounds like an enormous leap of faith that is not supported by either science or reason, youre not alone. In their book, Barrow and Tipler go even further, offering the following alternative interpretations of the anthropic princple:
Every one of these scenarios might present a fascinating feast for the imagination, but they all represent incredibly speculative leaps in logic, and make assumptions about cosmic purpose and the relationship between observers and reality that arent necessarily true.
We can certainly imagine an arbitrarily large number of possible configurations for our Universe and the laws and constants that govern it, and we can be certain that our Universe is one of the ones that admit the existence of intelligent observers. However, neither this nor any other anthropic argument can tell us anything meaningful about entities that are not in some way tied to physical observables.
You dont have to look far to find claims that the anthropic principle does any or all of the following: supports a multiverse, provides evidence for the string landscape, requires we have a Jupiter-like gas giant to protect Earth from asteroids, and to explain why Earth is ~26,000 light-years away from the galactic center. In other words, people are misusing the anthropic principle to argue that the Universe must be the way it is because we exist with the properties that we have. Thats not only untrue, but its not even what the anthropic principle allows us to conclude.
Whats true is that we do exist, the laws of nature exist, and some of the great cosmic unknowns can be legitimately constrained by the facts of our existence. In that sense and perhaps, in that sense alone the anthropic principle has scientific value. But as soon as we start speculating about relationships, causes, or phenomena that we cannot detect or measure, we leave science behind.
That isnt to say that such speculations arent intellectually interesting, but engaging in them in no way improves our understanding of the Universe the way that Hoyles or Weinbergs anthropic predictions did. The simple fact of our existence can guide us toward understanding what certain parameters that govern our Universe must actually be, but only if we stick to whats scientifically measurable, at least in principle.
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We exist. What can that fact teach us about the Universe? - Big Think
Chris Hedges: We Are Not the First Civilization to Collapse, but We Will Probably Be the Last – Scheerpost.com
The archeological remains of past civilizations, including those of the prehistoric Cahokia temple mound complex in Illinois, are sobering reminders of our fate.
By Chris Hedges / Original to ScheerPost
CAHOKIA MOUNDS, Illinois: I am standing atop a 100-foot-high temple mound, the largest known earthwork in the Americas built by prehistoric peoples. The temperatures, in the high 80s, along with the oppressive humidity, have emptied the park of all but a handful of visitors. My shirt is matted with sweat.
I look out from the structureknown asMonks Mound at the flatlands below, with smaller mounds dotting the distance. These earthen mounds, built at a confluence of the Illinois, Mississippi and Missouri rivers, are all that remain of one of the largest pre-Columbian settlements north of Mexico, occupied from around 800 to 1,400 AD by perhaps as many as 20,000 people.
Thisgreat city, perhaps the greatest in North America, rose, flourished, fell into decline and was ultimately abandoned. Civilizations die in familiar patterns. They exhaust natural resources. They spawn parasitic elites who plunder and loot the institutions and systems that make a complex society possible. They engage in futile and self-defeating wars. And then the rot sets in. The great urban centers die first, falling into irreversible decay. Central authority unravels. Artistic expression and intellectual inquiry are replaced by a new dark age, the triumph of tawdry spectacle and the celebration of crowd-pleasing imbecility.
Collapse occurs, and can only occur, in a power vacuum, anthropologistJoseph Tainterwrites inThe Collapse of Complex Societies. Collapse is possible only where there is no competitor strong enough to fill the political vacuum of disintegration.
Several centuries ago, the rulers of thisvast city complex, which covered some 4,000 acres, including a 40-acre central plaza, stood where I stood. They no doubt saw below in the teeming settlements an unassailable power, with at least 120 temple mounds used as residences, sacred ceremonial sites, tombs, meeting centers and ball courts. Cahokia warriors dominated a vast territory from which they exacted tribute to enrich the ruling class of this highly stratified society. Reading the heavens, these mound builders constructed several circular astronomical observatories wooden versions of Stonehenge.
The citys hereditary rulers were venerated in life and death. A half mile from Monks Mound is the seven-foot-highMound72, in which archeologistsfoundthe remains of a man on a platform covered with 20,000 conch-shell disc beads from the Gulf of Mexico. The beads were arranged in the shape of a falcon, with the falcons head beneath and beside the mans head. Its wings and tail were placed underneath the mans arms and legs. Below this layer of shells was the body of another man, buried face downward. Around these two men were six more human remains, possibly retainers, who may have been put to death to accompany the entombed man in the afterlife. Nearby were buried the remains of 53 girls and women ranging in age from 15 to 30, laid out in rows in two layers separated by matting. They appeared to have been strangled to death.
The poetPaul Valrynoted, a civilization has the same fragility as a life.
Across the Mississippi River from Monks Mound, the city skyline of St. Louis is visible. It is hard not to see our own collapse in that of Cahokia. In 1950, St. Louis was the eighth-largest city in the United States, with a population of 856,796. Today, that numberhas fallento below 300,000, a drop of some 65 percent. Major employers Anheuser-Busch, McDonnell-Douglas, TWA, Southwestern Bell and Ralston Purina have dramatically reduced their presence or left altogether. St. Louis is consistentlyrankedone of the most dangerous cities in the country.One in fivepeoplelive inpoverty. The St. Louis Metropolitan Police Department has the highest rate ofpolice killingsper capita, of the 100 largest police departments in the nation, according to a 2021 report. Prisoners in the cityssqualid jails, where 47 peopledied in custodybetween 2009 and 2019, complain of water being shut off from their cells for hours and guards routinely pepper spraying inmates, including those on suicide watch. The citys crumbling infrastructure, hundreds of gutted and abandoned buildings, empty factories, vacant warehouses and impoverished neighborhoods replicate the ruins of other post-industrial American cities, the classic signposts of a civilization interminal decline.
Just as in the past, countries that are environmentally stressed, overpopulated, or both, become at risk of getting politically stressed, and of their governments collapsing,Jared Diamondargues inCollapse: How Societies Choose to Fail or Succeed.When people are desperate, undernourished and without hope, they blame their governments, which they see as responsible for or unable to solve their problems. They try to emigrate at any cost. They fight each other over land. They kill each other. They start civil wars. They figure that they have nothing to lose, so they become terrorists, or they support or tolerate terrorism.
Pre-industrial civilizations were dependent on the limits of solar energy and constrained by roads and waterways, impediments that were obliterated when fossil fuel became an energy source. As industrial empires became global, their increase in size meant an increase in complexity. Ironically, this complexity makes usmorevulnerable to catastrophic collapse, not less. Soaring temperatures (Iraq is enduring120 degree heatthat has fried the countrys electrical grid), the depletion of natural resources, flooding, droughts, (the worst drought in 500 years is devastating Western, Central and Southern Europe and is expected tosee a declinein crop yields of 8 or 9 percent), power outages, wars, pandemics,a rise inzoonotic diseases and breakdowns in supply chains combine to shake the foundations of industrial society. The Arctic has beenheating upfour times faster than the global average, resulting in an accelerated melting of the Greenland ice sheet and freakish weather patterns. The Barents Sea north of Norway and Russiaare warmingup to seven times faster. Climate scientists did not expect this extreme weather until2050.
Each time history repeats itself, the price goes up, the anthropologistRonald Wrightwarns, calling industrial society a suicide machine.
InA Short History of Progress,he writes:
Civilization is an experiment, a very recent way of life in the human career, and it has a habit of walking into what I am calling progress traps. A small village on good land beside a river is a good idea; but when the village grows into a city and paves over the good land, it becomes a bad idea.While prevention might have been easy, a cure may be impossible: a city isnt easily moved. This human inability to foresee or to watch out for long-range consequences may be inherent to our kind, shaped by the millions of years when we lived from hand to mouth by hunting and gathering. It may also be little more than a mix of inertia, greed, and foolishness encouraged by the shape of the social pyramid. The concentration of power at the top of large-scale societies gives the elite a vested interest in the status quo; they continue to prosper in darkening times long after the environment and general populace begin to suffer.
Wright alsoreflects uponwhat will be left behind:
The archaeologists who digusup will need to wear hazmat suits. Humankind will leave a telltale layer in the fossil record composed of everything we produce, from mounds of chicken bones, wet-wipes, tires, mattresses and other household waste to metals, concrete, plastics, industrial chemicals, and the nuclear residue of power plants and weaponry. We are cheating our children, handing them tawdry luxuries and addictive gadgets while we take away whats left of the wealth, wonder and possibility of the pristine Earth.
Calculations of humanitys footprint suggest we have been in ecological deficit, taking more than Earths biological systems can withstand, for at least 30 years. Topsoil is being lost far faster than nature can replenish it; 30 percent of arable land has been exhausted since the mid-20th century.
We have financed this monstrous debt by colonizing both past and future, drawing energy, chemical fertilizer and pesticides from the planets fossil carbon, and throwing the consequences onto coming generations of our species and all others. Some of those species have already been bankrupted: they are extinct. Others will follow.
As Cahokia declined, violence dramaticallyincreased. Surrounding towns were burned to the ground. Groups, numbering in the hundreds, were slaughtered and buried in mass graves. At the end, the enemy killed all people indiscriminately. The intent was not merely prestige, but an early form of ethnic cleansing writes anthropologist Timothy R. Pauketat, inAncient Cahokia and the Mississippians.He notes that, in one fifteenth-century cemetery in central Illinois, one-third of all adults had been killed by blows to the head, arrow wounds or scalping. Many showed evidence of fractures on their arms from vain attempts to fight off their attackers.
Suchdescent intointernecine violence is compounded by a weakened and discredited central authority. In the later stages of Cahokia, the ruling class surrounded themselves with fortified wooden stockades, including a two-mile long wall that enclosed Monks Mound. Similar fortifications dotted the vast territory the Cahokia controlled, segregating gated communities where the wealthy and powerful, protected by armed guards, sought safety from the increasing lawlessness and hoarded dwindling food supplies and resources.
Overcrowding inside these stockades saw the spread of tuberculosis and blastomycosis, caused by a soil-borne fungus, along with iron deficiency anemia. Infant mortality rates rose, and life spans declined, a result of social disintegration, poor diet and disease.
By the 1400s Cahokia had beenabandoned. In 1541, when Hernando de Sotos invading army descended on what is today Missouri, looking for gold, nothing but the great mounds remained, relics of a forgotten past.
This time thecollapsewill be global. It will not be possible, as in ancient societies, to migrate to new ecosystems rich in natural resources. The steady rise in heat will devastate crop yields and make much of the planet uninhabitable. Climate scientistswarn thatonce temperaturesrise by 4, the earth, at best, will be able to sustain a billion people.
The more insurmountable the crisis becomes, the more we, like our prehistoric ancestors, will retreat intoself-defeating responses,violence, magical thinking anddenial.
The historianArnold Toynbee, who singled out unchecked militarism as the fatal blow to past empires,arguedthat civilizations are not murdered, but commit suicide. They fail to adapt to a crisis, ensuring their own obliteration. Our civilizations collapse will be unique in size, magnified by the destructive force of our fossil fuel-driven industrial society. But it will replicate the familiar patterns of collapse that toppled civilizations of the past. The difference will be in scale, and this time there will be no exit.
NOTE TO SCHEERPOST READERS FROM CHRIS HEDGES:There is now no way left for me to continue to write a weekly column for ScheerPost and produce my weekly television show without your help.The walls are closing in, with startling rapidity, on independent journalism, with the elites, including the Democratic Party elites, clamoring for more and more censorship. Bob Scheer, who runs ScheerPost on a shoestring budget, and I will not waver in our commitment to independent and honest journalism, and we will never put ScheerPost behind a paywall, charge a subscription for it, sell your data or accept advertising. Please, if you can, sign up atchrishedges.substack.comso I can continue to post my now weekly Monday column on ScheerPost and produce my weekly television show, The Chris Hedges Report.
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This Curvy Quantum Physics Discovery Could Revolutionize Our Understanding of Reality – The Debrief
A recent discovery in the field of quantum physics by researchers at Purdue University has opened the doorway to a whole new way of looking at our physical reality.
According to the researchers involved, an all-new technique that can allow the creation of curved surfaces that behave like flat ones may completely revolutionize our understanding of curvature and distance, as well as our knowledge of quantum physics.
As a fundamental principle, if one wants to create a curved surface even at the microscopic level, one must start with a flat surface and bend it. Although this may seem self-evident, suchprinciples are critical guidelines for researchers who work in quantum mechanics, information processing, astrophysics, and a whole host of scientific disciplines.
However, according to the Purdue research team behind this latest discovery, they have discovered a way to break that law, resulting in a curved space that behaves at a quantum level like a flat one. Thediscovery is, in short, something that appears to break the sorts of fundamental rules many physicists take for granted.
Our work may revolutionize the general publics understanding of curvatures and distance, said Qi Zhou, a Professor of Physics and Astronomy who is also a co-author of the paper announcing the research teams potentially groundbreaking results. It has also answered long-standing questions in non-Hermitian quantum mechanics by bridging non-Hermitian physics and curved spaces.
Published in the journal Nature Communications, the paper and its authors explain that the discovery involves the construction of curved surfaces that behave like flat ones, particularly at the quantum level, resulting in a system they describe as non-Hermitian.
For example, quantum particles on a theoretical lattice can hop from one location to another instantaneously. If the chances of that particle hopping either left or right is equal, then that system is referred to as Hermitian. However, if the odds are unequal, then the system is non-Hermitian.
Typical textbooks of quantum mechanics mainly focus on systems governed by Hamiltonians that are Hermitian, said graduate student Chenwei Lv, who is also the lead author of the paper. As a result, the team notes that there is very little literature about their discovery.
A quantum particle moving in a lattice needs to have an equal probability to tunnel along the left and right directions, Lv explains before offering examples where certain systems lose this equal probability. In such non-Hermitian systems, familiar textbook results no longer apply, and some may even look completely opposite to that of Hermitian systems.
Lv and the Purdue team found that a non-Hermitian system actually curved the space where a quantum particle resides. In that case, they explain, a quantum particle in a lattice with nonreciprocal tunneling is actually moving on a curved surface. Lv notes that these types of non-Hermitian systems are in sharp contrast to what first-year undergraduate quantum physics students are taught from day one of their education.
These extraordinary behaviors of non-Hermitian systems have been intriguing physicists for decades, Lv adds, but many outstanding questions remain open.
Professor Ren Zhang from Xian Jiaotong University, who was a co-author of the study, says that their research and its unexpected results have implications in two distinct areas.
On the one hand, it establishes non-Hermiticity as a unique tool to simulate intriguing quantum systems in curved spaces, he explained. Most quantum systems available in laboratories are flat, and it often requires significant efforts to access quantum systems in curved spaces.That non-Hermiticity, adds Zhang, offers experimentalists an extra knob to access and manipulate curved spaces.
On the other hand, says Zhang, the duality allows experimentalists to use curved spaces to explore non-Hermitian physics. For instance, our results provide experimentalists a new approach to access exceptional points using curved spaces and improve the precision of quantum sensors without resorting to dissipations.
The research team notes that their discovery could assist researchers across a wide array of disciplines, with future research spinning off in multiple directions.
First, those who study curved spaces could implement the Purdue teams apparatuses, while physicists working on non-Hermitian systems could tailor dissipations to access non-trivial curved spaces that cannot be easily obtained by conventional means.
In the end, Lv points to the broader implications of their discovery and its place in the world of quantum physics.
The extraordinary behaviors of non-Hermitian systems, which have puzzled physicists for decades, become no longer mysterious if we recognize that the space has been curved, said Lv.
In other words, non-Hermiticity and curved spaces are dual to each other, being the two sides of the same coin.
Connect with Author Christopher Plain on Twitter @plain_fiction
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This Curvy Quantum Physics Discovery Could Revolutionize Our Understanding of Reality - The Debrief
University of Warwick: Diamonds will shine a light on quantum mystery in new project at the University of Warwick and UCL – India Education Diary
A new project at the University of Warwick and UCL aims to answer a fundamental question of quantum physics, by attempting to make a diamond exist in a superposition of two places at once.
The ambitious experiment may one-day lead to a long sought-after test of the quantum nature of gravity, through a method that was pioneered in a joint work by a team of researchers from UCL, Warwick and a host of other universities.
The project has been made possible by a grant of 500,000 from the Science and Technology Facilities Council from their Quantum Technology for Fundamental Physics programme. Seventeen new projects will tackle fundamental research questions with quantum technology from the exploration of antimatter gravity to dark matter detection.
UK Research and Innovation (UKRI) is investing 6 million towards that endeavour and in support of its existing Quantum Technologies for Fundamental Physics (QTFP) programme. The programme receives joint funding from the Science and Technology Facilities Council (STFC) and the Engineering and Physical Sciences Research Council (EPSRC).
Quantum mechanics allows for an object, however big, to be described as existing in different places at once. This is called a spatial superposition. Despite being counter-intuitive and in direct conflict with our everyday experience, the superposition principle of quantum mechanics has been experimentally verified using atoms and molecules.
Physicists at the University of Warwick will use tiny synthetic diamonds, called nanodiamonds which are just one micron across to explore if larger objects can exhibit quantum behaviours. The researchers will work with collaborators at Element Six (www.e6.com) and the University of Cardiff to make nanodiamonds with a single precise imperfection. This defect in the highly regular structure of a diamond is called a nitrogen-vacancy centre (NVC).
The NVC has a useful magnetic quantum property called spin. Spin can be described as being in either a spin up state, a spin down state, or a quantum superposition of both states at once.
The spin embedded in the nanodiamond will be put into such a superposition state by external pulses of microwaves. The Warwick team is well-practiced at this technique, while the UCL team was involved in proposing the underpinning theory. However, for this project they will also attempt to do it while the nanodiamond is magnetically levitated and so able to move freely over long distances.
The researchers believe that using this experimental set-up, the nanodiamond will go into a superposition of moving in opposite directions corresponding to the superposition of its spin states and thus be in a superposition of two places at once.
Nitrogen-vacancy centres in diamond are a powerful platform for several quantum technologies including quantum computing, quantum communication and quantum sensing. The scientists expect that their work in this project will advance these quantum technologies and should lead to a new class of more sensitive sensors based on levitated nanodiamonds in a superposition.
Dr Gavin Morley of the Department of Physics at Warwick said: Atoms and molecules are very well described by quantum mechanics, but what about much larger things? The project has the ambitious goal of testing whether levitated nanodiamonds made up of more than a million times more atoms can display this quantum behaviour.
Quantum mechanics and general relativity are our best explanations of the physical world but, for me, understanding how to make them work together is the most interesting problem in physics. Levitating nanodiamonds provide a pathway to eventually doing the experiments that could unlock this deep puzzle.
Professor Sougato Bose of UCL said: We are thrilled that this offers us the opportunity to take a very first step towards a quantum superposition with a crystal both here and there, which will eventually pave the way to testing the quantum nature of gravity.
Professor Grahame Blair, STFC Executive Director, Programmes, said: This new cohort of projects should make a valuable contribution to our understanding of the universe using cutting-edge quantum tech such as quantum computing, imaging, sensing and simulations.
The new grants continue to support the UK research community in exploring the diversity of quantum technology applications for fundamental science from neutrino mass studies to searches for violations of fundamental symmetries of nature.
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Schrdinger Believed That There Was Only One Mind in the Universe – Walter Bradley Center for Natural and Artificial Intelligence
Consciousness researcher Robert Prentner and cognitive psychologist will tell a prestigious music and philosophy festival in London next month that great physicist Donald Hoffman, quantum physicist Erwin Schrdinger (18871961) believed that The total number of minds in the universe is one. That is, a universal Mind accounts for everything.
In a world where many scientists strive mightily to explain how the human mind can arise from non-living matter, Prentner and Hoffman will tell the HowtheLightGetsIn festival in London (September 1718, 2022) that the author of the famous Cat paradox was hardly a materialist:
In 1925, just a few months before Schrdinger discovered the most basic equation of quantum mechanics, he wrote down the first sketches of the ideas that he would later develop more thoroughly in Mind and Matter. Already then, his thoughts on technical matters were inspired by what he took to be greater metaphysical (religious) questions. Early on, Schrdinger expressed the conviction that metaphysics does not come after physics, but inevitably precedes it. Metaphysics is not a deductive affair but a speculative one.
Inspired by Indian philosophy, Schrdinger had a mind-first, not matter-first, view of the universe. But he was a non-materialist of a rather special kind. He believed that there is only one mind in the universe; our individual minds are like the scattered light from prisms:
A metaphor that Schrdinger liked to invoke to illustrate this idea is the one of a crystal that creates a multitude of colors (individual selves) by refracting light (standing for the cosmic self that is equal to the essence of the universe). We are all but aspects of one single mind that forms the essence of reality. He also referred to this as the doctrine of identity. Accordingly, a non-dual form of consciousness, which must not be conflated with any of its single aspects, grounds the refutation of the (merely apparent) distinction into separate selves that inhabit a single world.
But in Mind and Matter (1958), Schrdinger, we are told, took this view one step further:
Schrdinger drew remarkable consequences from this. For example, he believed that any man is the same as any other man that lived before him. In his early essay Seek for the Road, he writes about looking into the mountains before him. Thousands of years ago, other men similarly enjoyed this view. But why should one assume that oneself is distinct from these previous men? Is there any scientific fact that could distinguish your experience from another mans? What makes you you and not someone else? Similarly as John Wheeler once assumed that there is really only one electron in the universe, Schrdinger assumed that there really is only one mind. Schrdinger thought this is supported by the empirical fact that consciousness is never experienced in the plural, only in the singular. Not only has none of us ever experienced more than one consciousness, but there is also no trace of circumstantial evidence of this ever happening anywhere in the world.
Most non-materialists will wish they had gotten off two stops ago. We started with Mind first, which when accounting for why there is something rather than nothing has been considered a reasonable assumption throughout history across the world (except among materialists). But the assumption that no finite mind could experience or act independently of the Mind behind the universe is a limitation on the power of that Mind. Why so?
Its not logically clear and logic is our only available instrument here why the original Mind could not grant to dogs, chimpanzees, and humans the power to apprehend and act as minds in their own right in their natural spheres not simply as seamless extensions of the universal Mind.
With humans, the underlying assumptions of Schrdingers view are especially problematic. Humans address issues of good and evil. If Schrdinger is right, for example, Dr. Martin Luther King, and Comrade Josef Stalin are really only one mind because each experienced only his own consciousness. But wait. As a coherent human being, each could only have experienced his own consciousness and not the other mans.
However, that doesnt mean that they were mere prisms displaying different parts of the spectrum of broken light. The prism analogy fails to take into account that humans can act for good or ill. Alternatively, it is saying that good and evil, as we perceive them, are merely different colors in a spectrum. As noted earlier, many of us should have got off two stops ago
In any event, Schrdingers views are certain to be an interesting discussion at HowLightGetsIn.
Schrdinger was hardly the only modern physicist or mathematician to dissent from materialism. Mathematician Kurt Gdel (19061978), to take one example, destroyed a popular form of atheism (logical positivism) via his Incompleteness Theorems.
The two thinkers held very different views, of course. But both saw the fatal limitations of materialism (naturalism) and they addressed these limitations quite differently. In an age when Stephen Hawkings disdain for philosophy is taken to be representative of great scientists, its a good thing if festivals like HowLightGetsIn offer a broader perspective and corrective.
You may also wish to read: Why panpsychism is starting to push out naturalism. A key goal of naturalism/materialism has been to explain human consciousness away as nothing but a pack of neurons. That cant work. Panpsychism is not a form of dualism. But, by including consciousness especially human consciousness as a bedrock fact of nature, it avoids naturalisms dead end.
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What is a QPU and how will it drive quantum computing? – IT-Online
A QPU, also known as a quantum processor, is the brain of a quantum computer that uses the behaviour of particles like electrons or photons to make certain kinds of calculations much faster than processors in todays computers.
By Rick Merritt, senior staff writer atNvidia
Just as GPUs and DPUs enableaccelerated computingtoday, theyre also helping a new kind of chip, the QPU, boot up the promise ofquantum computing.
In your hand, a quantum processing unit might look and feel very similar to a graphics or a data processing unit. Theyre all typically chips, or modules with multiple chips, but under the hood the QPU is a very different beast.
So whats a QPU?
A QPU, aka a quantum processor, is the brain of a quantum computer that uses the behaviour of particles like electrons or photons to make certain kinds of calculations much faster than processors in todays computers.
QPUs rely on behaviours like superposition, the ability of a particle to be in many states at once, described in the relatively new branch of physics called quantum mechanics.
By contrast, CPUs, GPUs and DPUs all apply principles of classical physics to electrical currents. Thats why todays systems are called classical computers.
QPUs could advance cryptography, quantum simulations and machine learning and solve thorny optimisation problems.
How does a quantum processor work?
CPUs and GPUs calculate in bits, on/off states of electrical current that represent zeros or ones. By contrast, QPUs get their unique powers by calculating in qubits quantum bits that can represent many different quantum states.
A qubit is an abstraction that computer scientists use to express data based on the quantum state of a particle in a QPU. Like the hands on a clock, qubits point to quantum states that are like points in a sphere of possibilities.
The power of a QPU is often described by the number of qubits it contains. Researchers are developing additional ways to test and measure the overall performance of a QPU.
Many ways to make a qubit
Corporate and academic researchers are using a wide variety of techniques to create the qubits inside a QPU.
The most popular approach these days is called a superconducting qubit. Its basically made from one or more tiny metallic sandwiches called Josephson junctions, where electrons tunnel through an insulating layer between two superconducting materials.
Qubits inside IBMs Eagle superconducting QPU.
The current state of the art creates more than 100 of these junctions into a single QPU. Quantum computers using this approach isolate the electrons by cooling them to temperatures near absolute zero with powerful refrigerators that look like high-tech chandeliers.
Qubits inside IBMs Eagle superconducting QPU.
A qubit of light
Some companies use photons rather than electrons to form qubits in their quantum processors. These QPUs dont require expensive, power-hungry refrigerators, but they need sophisticated lasers and beam splitters to manage the photons.
Researchers are using and inventing other ways to create and connect qubits inside QPUs. For example, some use an analogue process called quantum annealing, but systems using these QPUs have limited applications.
Its early days for quantum computers, so its not yet clear what sorts of qubits in what kinds of QPUs will be widely used.
Simple chips, exotic systems
Theoretically, QPUs may require less power and generate less heat than classical processors. However, the quantum computers they plug into can be somewhat power hungry and expensive.
Thats because quantum systems typically require specialised electronic or optical control subsystems to precisely manipulate particles. And most require vacuum enclosures, electromagnetic shielding or sophisticated refrigerators to create the right environment for the particles.
D-Wave shows qubits and QPU in a full system.
Thats one reason why quantum computers are expected to live mainly in supercomputing centers and large data centres.
QPUs do cool stuff
Thanks to the complex science and technology, researchers expect the QPUs inside quantum computers will deliver amazing results. They are especially excited about four promising possibilities.
First, they could take computer security to a whole new level.
Quantum processors can factor enormous numbers quickly, a core function in cryptography. That means they could break todays security protocols, but they can also create new, much more powerful ones.
In addition, QPUs are ideally suited to simulating the quantum mechanics of how stuff works at the atomic level. That could enable fundamental advances in chemistry and materials science, starting domino effects in everything from the design of lighter airplanes to more effective drugs.
Researchers also hope quantum processors will solve optimization problems classical computers cant handle in fields like finance and logistics. And finally, they may even advance machine learning.
So when will QPUs be available?
For quantum researchers, QPUs cant come soon enough. But challenges span the gamut.
On the hardware level, QPUs are not yet powerful or dependable enough to tackle most real-world jobs. However, early QPUs and GPUs simulating them with software likeNvidia cuQuantum are beginning to show results that help researchers, especially in projects exploring how to build better QPUs and develop quantum algorithms.
Researchers are using prototype systems available through several companies like Amazon, IBM, IonQ, Rigetti, Xanadu and more. Governments around the world are beginning to see the promise of the technology, so theyre making significant investments to build ever larger and more ambitious systems.
How do you program a quantum processor?
Software for quantum computing is still in its infancy.
Much of it looks like the kind of assembly-language code programmers had to slog through in the early days of classical computers. Thats why developers have to understand the details of the underlying quantum hardware to get their programs running.
But here, too, there are real signs of progress toward the holy grail a single software environment that will work across any supercomputer, a sort of quantum OS.
Several early projects are in the works. All struggle with the limitations of the current hardware; some are hampered by the limits of the companies developing the code.
For example, some companies have deep expertise in enterprise computing but lack experience in the kind of high-performance environments where much of the scientific and technical work in quantum computing will be done. Others lack expertise in AI, which has synergies with quantum computing.
Enter hybrid quantum systems
The research community widely agrees that for the foreseeable future, classical and quantum computers will work in tandem. So, software needs to run well across QPUs, CPU and GPUs, too.
Researchers described a hybrid classical-quantum computer in a 2017 paper.
To drive quantum computing forward, Nvidia recently announced theNvidia Quantum Optimized Device Architecture(QODA), an open platform for programming hybrid quantum systems.
QODA includes a high-level language thats concise and expressive so its powerful and easy to use. With QODA, developers can write programs that run on QPUs in quantum computers and GPUs simulating QPUs in classical systems.
Nvidia QODA provides developers a unified platform for programming any hybrid quantum-classical computer.
QODA will support every kind of quantum computer and every sort of QPU.
At its launch, quantum system and software providers including Pasqal, Xanadu, QC Ware and Zapata expressed support for QODA. Users include major supercomputing centers in the US and Europe.
QODA builds on NVIDIAs extensive expertise in CUDA software, which accelerates HPC and AI workloads for scientific, technical and enterprise users.
With a beta release of QODA expected before the end of the year, the outlook for QPUs in 2023 and beyond is bright.
Related
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What is a QPU and how will it drive quantum computing? - IT-Online
The Origin of Zero to What Earths Minerals Can Tell Us About Aliens (The Galaxy Report) – The Daily Galaxy –Great Discoveries Channel
Posted on Aug 3, 2022 in Astrobiology, Astronomy, Astrophysics, Consciousness, Cosmology, Exoplanets, Extraterrestrial Life, James Webb Space Telescope, Milky Way Galaxy, Science, Science News, Space News, Supernova, Technology, Universe
Todays stories range from Could We Use the Suns Gravity to Find Alien Life to The Source of Mysterious Infrared Light to When Will the Milky Ways Next Supernova Occur?
When Will the Next Supernova in Our Galaxy Occur? Scientists have new tools at their disposal to detect and study the dramatic explosion of a star, reports Dan Falk for The Smithsonian. Its been a long wait418 years since weve seen a star explode in our galaxy. So are we overdue for a bright, nearby supernova?
The Elusive Origin of Zero--Who decided that nothing should be something? reports Scientific American. Historians, journalists and others have variously identified the symbols birthplace as the Andes mountains of South America, the flood plains of the Tigris and Euphrates Rivers, the surface of a calculating board in the Tang dynasty of China, a cast iron column and temple inscriptions in India, and most recently, a stone epigraphic inscription found in Cambodia.The tracing of zeros heritage has been elusive.
Could we use the Suns gravity to find alien life?With a telescope at just the right distance from the Sun, we could use its gravity to enhance and magnify a potentially inhabited planet, reports Big Think. Our strongest nearby source of gravity, the Sun, is itself capable of producing a gravitational lens, but only if the geometry is right: conditions that dont begin until were 547 times the Earth-Sun distance away.
What if the reality we perceive is just an evolutionary trick? Do we see the world as it really is? Perhaps not. Maybe even likely not, says Robert Prentner in this YouTube video
With New Study, NASA Seeks the Science behind UFOs--Although modest in scope, a NASA research project reflects shifting attitudes toward the formerly taboo subject of UFOs, reports Adam Mann for Scientific American. NASAs announcement fits in with the suddenly more open-minded zeitgeist regarding UAPs.
Life Helps Make Almost Half of All Minerals on EarthA new origins-based system for classifying minerals reveals the huge geochemical imprint that life has left on Earth. It could help us identify other worlds with life too, reports Quanta.
Where Do Space, Time and Gravity Come From? Einsteins description of curved space-time doesnt easily mesh with a universe made up of quantum wavefunctions. Theoretical physicist Sean Carroll discusses the quest for quantum gravity with host Steven Strogatz at Quanta.com
AI Is Discovering Its Own Fundamental Physics And Scientists Are BaffledAI observed videos of lava lamps and inflatable air dancers and identified dozens of physics variables that scientists dont yet understand, reports Vice Science.
Schrodinger Believed the Universe is One Universal Mind. The quantum physicist and author of the famous Cat Paradox believed that our individual minds are not unique but rather like the reflected light from prisms, reports Mind Matters.
Discovery of new exoplanet raises questions about planet formation, reports University of Florida. The Jupiter-sized world offers two key opportunities to scientists studying how all planets, including those in our own solar system, develop. A mere 1.5-million-year-old infant compared to its probable lifespan of billions of years, the planet is so young it can still provide clues about its birth.
Webb captures stellar gymnastics in the Cartwheel Galaxy, reports the ESA. Webbs high-precision instruments resolved individual stars and star-forming regions within the Cartwheel, and revealed the behavior of the black hole within its galactic center. These new details provide a renewed understanding of a galaxy in the midst of a slow transformation.
Dark Matter Mapped Around Distant Galaxies, reports Physics,com. Gravitational lensing of the cosmic microwave background has been used to probe the distribution of dark matter around some of the earliest galaxies in the Universe.
Is the James Webb Space Telescope finding the furthest, oldest, youngest or first galaxies? An astronomer explains Michael J. I. Brown explains for Space.com
Cosmic Buckyballs Could Be The Source of Mysterious Infrared Light, reports Science Alert. Unidentified Infrared Emission (UIE) bands have baffled scientists for decades; according to a theoretical new work, at least some of these bands can be produced by highly ionized buckminsterfullerene, more commonly known as buckyballs.
Astronomers discover 21 new extremely low-mass white dwarf candidates, reports Phys,org. Extremely low-mass (ELM) white dwarfs (WDs) are rare objects, found with only few exceptions in short-period binaries.
Particle Physicists Puzzle Over a New Duality A hidden link has been found between two seemingly unrelated particle collision outcomes. Its the latest example of a mysterious web of mathematical connections between disparate theories of physics, reports Katie McCormick for Quanta.com
A New Private Moon Race Kicks Off Soon Commercial spacecraft are vying to land on the lunar surface, but can they jump-start a new space economy? reports Scientific American.
Image credit top of page: ESO Observatories, Chile
Curated by The Daily Galaxy Editorial Staff
The Galaxy Report newsletter brings you twice-weekly news of space and science that has the capacity to provide clues to the mystery of our existence and add a much needed cosmic perspective in our current Anthropocene Epoch.
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Post-doctoral Fellow / Research Assistant I/II, Department of Civil Engineering job with THE UNIVERSITY OF HONG KONG | 303412 – Times Higher Education
Work type: Full-timeDepartment: Department of Civil Engineering (14100)Categories: Academic-related Staff
Quantum Computation and Simulation Applications Development
Applications are invited for appointment as Post-doctoral Fellow/Research Assistant I/II in Quantum Computation and Simulation Applications Development in the Department of Civil Engineering (Ref.: 515642), to commence as soon as possible for one year, with the possibility of renewal subject to satisfactory performance.
We are seeking a highly-motivated individual who is passionate to develop quantum computation and simulation applications for environmental engineering and related challenges. Applicants should preferably possess a Ph.D. degree or equivalent in Quantum Simulation and Computation, Quantum Information Science, Computer Science, Data Science, Bioinformatics. However, we also welcome application from applicants with a strong interest in this area and possess a Ph.D. degree or equivalent in Civil and Environmental Engineering, Physics, Biology, Chemistry, Statistics, Mathematics, or other STEM disciplines.
The appointee should have an inquisitive mind, risk-taking attitude, a willingness to learn new skills and the ability to creatively tackle complex problems. Proficiency in Python is preferred but not required. Basic knowledge in quantum computation, quantum information, or quantum physics and exposure to the IBM QISKit quantum programming stack would be an advantage. Those who plan to pursue research postgraduate studies are welcome to apply. Those with lower qualifications and/or less experience may be considered for appointment as Research Assistant I/II.
The appointee will be part of an international joint research collaboration between HKU and Imperial College London (UK), co-led by Dr. Amy Tan and Dr. Po-Heng (Henry) Lee. The appointee will be working within an international and interdisciplinary group to develop quantum computation and simulation applications to tackle grand challenges in environmental sustainability and livable city. Specific topic(s) of research would be dependent on the appointees skillsets and knowledge domain. Examples of research topics could include environmental microbiology and biotechnology, waste management, circular resources, resilient city, etc. Areas that the appointee might be required to undertake include quantum machine learning, quantum optimization, fault-tolerant codes and their decoding algorithms, quantum circuit synthesis and optimization, quantum computational complexity, etc. The appointee will also assist in grant applications, conduct presentations, prepare reports for funded projects, and other ad-hoc duties.
Enquiries about the duties of the post should be sent to Dr. Amy Tan and/or Dr Po-Heng (Henry) Lee at gyatan@hku.hk and po-heng.lee@imperial.ac.uk, respectively.
A highly competitive salary commensurate with qualifications and experience will be offered, in addition to annual leave and medical benefits. At current rates, salaries tax does not exceed 15% of gross income.
The University only accepts online application for the above post. Applicants should apply online and upload an up-to-date C.V. Review of applications will commence as soon as possible and continue until August 25, 2022, or until the post is filled, whichever is earlier.
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Lasers are weird and amazing – Big Think
The supermarket checkout scanner, the printer in your office, the pointer used in yesterdays meeting lasers are pretty much a part of everyday life now. You think about them very little, even as they do amazing things like instantly read barcodes or correct your nearsightedness via LASIK surgery.
But what is a laser, really? What makes them so special and so useful? Indeed, what makes a laser different from a simple lightbulb? The answers rest in the remarkable weirdness of quantum physics. Lasers are a quintessential quantum phenomenon.
The key question we have to deal with here is the interaction of light and matter. In classical physics, light is made of waves of electromagnetic energy traveling through space. These waves can be emitted or absorbed by accelerating electrically charged particles of matter. This is what happens in a radio tower: Electrical charges are accelerated up and down the tower to create the electromagnetic waves that travel through space to your car and let you listen to your station of choice.
At the turn of the century, scientists wanted to apply this classical idea to create models of atoms. They imagined an atom as a little solar system, with the positively charged protons at the center and the negatively charged electrons orbiting around them. If an electron emitted or absorbed some light, i.e. electromagnetic energy, it would speed up or slow down. But this model didnt hold. For one thing, there is always an acceleration happening when one thing orbits another this is called centripetal acceleration. So the electron in this classical model of the atom must always be emitting radiation as it orbits and thereby losing energy. That makes the orbit unstable. The electron would quickly fall onto the proton.
Niels Bohr got around this problem with a new model of the atom. In the Bohr model, an electron can only occupy a set of discrete orbits around the proton. These orbits were visualized like circular train tracks that the electrons rode as they circled about the proton. The farther out an orbit was from the proton, the more excited it was, and the more energy it held.
In the Bohr model, the emission and absorption of light was all about electrons jumping between these orbits. To emit light, an electron jumped from a higher orbit down to a lower orbit, emitting a packet of light energy called a photon. An electron could also jump from a lower orbit to a higher one if it absorbed one of these light packets. The wavelength of the light emitted or absorbed was directly related to the energy difference between the orbits.
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There was much quantum weirdness in all of this. If the electron was bound to these orbits, that meant it was never between them. It jumped from one location to the other without ever occupying the intervening space. Also, light was both a particle a photon that had a packet of energy and a wave spread out through space. How do you imagine that? While the Bohr model was only a first step, modern versions of the theory still feature discrete energy levels and photon wave-particle duality.
How does this relate to lasers? LASER stands for Light Amplification Through Stimulated Emission of Radiation. The ideas of amplification and stimulated emission in a laser are based on those specific energy levels of electrons in atoms.
To make a laser, you take some material and exploit its quantum energy levels.
The first step is to invert the population of the levels. Usually, most electrons will reside in the atoms lowest energy levels that is where they like to rest. But lasers rely on boosting most of the electrons to a higher, excited level also called an excited state. This is done using a pump that pushes the electrons up to a specific excited state. Then, as some of these electrons begin spontaneously falling down again, they emit a specific wavelength of light. These photons travel through the material and tickle other electrons in the excited state, stimulating them to jump down, and causing more photons of the same wavelength to be emitted. By placing mirrors at either end of the material, this process builds up until there is a nice, steady beam of photons that are all the same wavelength. Some fraction of synchronized photons then escapes through a hole in one of the mirrors. That is the beam you see coming from your laser pointer.
This is exactly what does not happen in a light bulb, where atoms in the heated filament have electrons jumping up and down chaotically between different levels. The photons they emit have a wide range of wavelengths, which causes their light to look white. It is only by exploiting the weird quantum levels of electrons in an atom, the weird quantum jumps between those levels, and finally, the weird wave-particle duality of light itself, that those amazing and very useful lasers come into being.
There is, of course, a lot more to this story. But the basic idea you want to remember next time youre at the grocery store check-out is simple. A world beyond your perception the nanoworld of atoms is incredibly different from the one you live in. Somehow, we humans have peered into that tiny realm and come back with a deep enough understanding to reshape the macroworld we inhabit.
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