Category Archives: Quantum Physics
Diamonds Are a Quantum Scientist’s Best Friend: Discovery May Revolutionize the High-Tech Industry – SciTechDaily
Professor Somnath Bhattacharyya next to the vapor deposition chamber that is used to produce diamonds in the lab. Credit: Wits University
The discovery of triplet spin superconductivity in diamonds has the potential to revolutionize the high-tech industry.
Diamonds have a firm foothold in our lexicon. Their many properties often serve as superlatives for quality, clarity, and hardiness. Aside from the popularity of this rare material in ornamental and decorative use, these precious stones are also highly valued in industry where they are used to cut and polish other hard materials and build radiation detectors.
More than a decade ago, a new property was uncovered in diamonds when high concentrations of boron are introduced to it superconductivity. Superconductivity occurs when two electrons with opposite spin form a pair (called a Cooper pair), resulting in the electrical resistance of the material being zero. This means a large supercurrent can flow in the material, bringing with it the potential for advanced technological applications. Yet, little work has been done since to investigate and characterize the nature of a diamonds superconductivity and therefore its potential applications.
New research led by Professor Somnath Bhattacharyya in the Nano-Scale Transport Physics Laboratory (NSTPL) in the School of Physics at the University of the Witwatersrand in Johannesburg, South Africa, details the phenomenon of what is called triplet superconductivity in diamond. Triplet superconductivity occurs when electrons move in a composite spin state rather than as a single pair. This is an extremely rare, yet efficient form of superconductivity that until now has only been known to occur in one or two other materials, and only theoretically in diamonds.
Professor Somnath Bhattacharyya next to a dilution fridge a specialised piece of equipment that enables quantum properties of diamond. Credit: Wits University
In a conventional superconducting material such as aluminum, superconductivity is destroyed by magnetic fields and magnetic impurities, however triplet superconductivity in a diamond can exist even when combined with magnetic materials. This leads to more efficient and multifunctional operation of the material, explains Bhattacharyya.
The teams work has recently been published in an article in the New Journal of Physics, titled Effects of Rashba-spin-orbit coupling on superconducting boron-doped nanocrystalline diamond films: evidence of interfacial triplet superconductivity. This research was done in collaboration with Oxford University (UK) and Diamond Light Source (UK). Through these collaborations, beautiful atomic arrangement of diamond crystals and interfaces that have never been seen before could be visualized, supporting the first claims of triplet superconductivity.
Professor Somnath Bhattacharyya and members of the Wits Nano-Scale Transport Physics Lab. They are Professor Yorick Hardy, Dr Christopher Coleman, Kayleigh Mathieson and Professor Somnath Bhattacharyya. Credit: Wits University
Practical proof of triplet superconductivity in diamonds came with much excitement for Bhattacharyya and his team. We were even working on Christmas day, we were so excited, says Davie Mtsuko. This is something that has never been before been claimed in diamond, adds Christopher Coleman. Both Mtsuko and Coleman are co-authors of the paper.
Despite diamonds reputation as a highly rare and expensive resource, they can be manufactured in a laboratory using a specialized piece of equipment called a vapor deposition chamber. The Wits NSTPL has developed their own plasma deposition chamber which allows them to grow diamonds of a higher than normal quality making them ideal for this kind of advanced research.
This finding expands the potential uses of diamond, which is already well-regarded as a quantum material. All conventional technology is based on semiconductors associated with electron charge. Thus far, we have a decent understanding of how they interact, and how to control them. But when we have control over quantum states such as superconductivity and entanglement, there is a lot more physics to the charge and spin of electrons, and this also comes with new properties, says Bhattacharyya. With the new surge of superconducting materials such as diamond, traditional silicon technology can be replaced by cost effective and low power consumption solutions.
The induction of triplet superconductivity in diamond is important for more than just its potential applications. It speaks to our fundamental understanding of physics. Thus far, triplet superconductivity exists mostly in theory, and our study gives us an opportunity to test these models in a practical way, says Bhattacharyya.
Reference: Effects of Rashba-spinorbit coupling on superconducting boron-doped nanocrystalline diamond films: evidence of interfacial triplet superconductivity by Somnath Bhattacharyya, Davie Mtsuko, Christopher Allen and Christopher Coleman, 14 September 2020, New Journal of Physics.DOI: 10.1088/1367-2630/abafe9
The rest is here:
The many paths of muon math | symmetry magazine – Symmetry magazine
Like racecars on a track, thousands of particles called muons zip around an experiments giant 50-foot circular magnet at 99.9% of the speed of light. After making a few hundred laps in less than a millisecond, the muons decay and are soon replaced by another bunch.
The goal of the experiment, Fermilab Muon g-2, is to better understand the properties of muons, which are essentially heavier versions of electrons, and use them to probe the limitations of the Standard Model of particle physics. Specifically, physicists want to know about the muons magnetic momentthat is, how much do they rotate on their axes in a powerful magnetic field as they race around the magnet?
In 2001, an experiment at the US Department of Energys Brookhaven National Lab found that the muons turned more than theory predicted. The result surprised the physics community: If there really were a discrepancy, it could be a hint of new physics, like some as-yet-unknown particle influencing the muon. Two decades later, physicists hope to resolve the matter. Fermilab Muon g-2 aims to quadruple the precision of the 2001 finding and determine whether experiment really disagrees with theory.
Theres another side to the search thoughone thats carried out not with particle accelerators and giant magnets, but with equations on blackboards and computer simulations. Since 2016, another group of physicists has been trying to update the theoretical prediction of the muons magnetic moment by combining the efforts of several groups.
In June, the Muon g-2 Theory Initiative, which comprises 132 physicists across 82 institutions, published its first prediction: They calculated the muons anomalous magnetic moment, or ,to be 116,591,810x10-11. The value differs subtly, but significantly from the 2001 experiment, which found to be 116,592,089x10-11. (Thats a difference of less than 3parts permillion, for those keeping score at home.)
This is the first time that the entire community has come together and reached a consensus on the Standard Model prediction of this quantity, says Aida X. El-Khadra, a physicist at the University of Illinois Urbana-Champaign and cofounder of the Theory Initiative. Previously, individual groups produced their own predictions of , which differed slightly from one another.
By combining their efforts, physicists in the Theory Initiative hope that theyll be able to come up with an ultra-precise prediction to complement the forthcoming result from the Fermilab Muon g-2 experiment. Both the experiment and the theory initiative receive support from DOEs Office of Science.
But just how do physicists predict something like the muons magnetic moment, and why does it take 132 of them?
Illustration by Sandbox Studio, Chicago with Ariel Davis
The first calculations of particle magnetic moments came in the 1920s, when physicists were just beginning to develop relativistic quantum mechanics. British theoretical physicist Paul Dirac, building on the work of Llewellyn Thomas and others, found the ultimate equation describing the electron and its spinthen conceived of as the electrons internal rotationand its magnetic moment. Dirac predicted this number, called g, to be exactly 2.
But atomic spectroscopy experiments soon found that g differedfrom that prediction by about 0.1%a so-called anomalous magnetic moment, e. In 1947, Julian Schwinger developed a theoretical explanation: The electron could emit and then reabsorb a virtual photon, which slightly changed its interaction with a magnetic field.
Every way that something can happen in nature will happen, says Tom Blum, a theoretical physicist at the University of Connecticut. If a particle starts from here and gets to there, it can take all possible paths to get from there to there. And what quantum field theory tells us is how to weight those paths.
The emission and absorption of a single virtual photon is just the most straightforward of these possible particle paths. Since Schwinger, physicists have been working to calculate increasingly unlikely possible paths that a particle can take. Ironically, the way they think about these paths is with a tool of Schwingers rival, Richard Feynman. To illustrate the paths and calculate their probabilities, Feynman developed his eponymously named diagrams.
Here, the Feynman diagram represents a muon (the Greek letter mu) moving left to right in a magnetic field (the squiggly line, which also denotes a photon).
The Feynman diagram for Schwingers path is slightly more complicatedthis time theres a squiggly blue line, the virtual photon being emitted and absorbed by the muon. This contributes approximately 0.00116 to . This is the vast majority of muons anomalous magnetic moment.
To make the task manageable, the Theory Initiative segmented the task of calculating the muons magnetic moment into each component. To get down to a precision of about 100 parts in a billion, physicists have had to calculate a lot more than just a single virtual photon.
Contributions to the anomalous magnetic moment come from the three different interactions the strong interaction, the weak interaction and quantum electrodynamics all contribute, Blum says.
There was at one point some thought that gravity would have an impact, but further investigation proved its role was too small.
Quantum electrodynamics, or QED, covers all the possible ways a photon can interact with a muon. To get better precision, physicists can account for more virtual photons. Each additional virtual photon has about 1/137th the chance of being produced and reabsorbed, so a Feynman diagram with two virtual photons contributes about 1 / 137 * 137to , three virtual photons contribute 1 / 137 * 137* 137, and so on. Physicists have even gone all the way to five virtual photons.
With five virtual photons, there are more than 10,000 possible paths, so there are a corresponding number of Feynman diagrams to calculate. Possibilities abound because virtual photons can split into a virtual electron and a virtual positron (the antimatter counterpart to an electron). This virtual pair can then annihilate back into a virtual photon. Describing these complex paths requires loops and squiggles that arc over each other. Five-photon Feynman diagrams look less like a traditional particle physics schematic and more like abstract art.
The weak force, which governs the radioactive decay of nuclei, also plays a role in influencing the muons magnetic moment. Unlike QED, which is mediated by the massless photon, the weak force is mediated by the massive W and Z bosons, which each weigh about 90 times the mass of a proton. The fact that the bosons are heavy makes it extremely unlikely that the muon would emit and absorb a virtual W or Z boson. But occasionally, it does happen.
Both QED and the contribution from the weak force can be calculated to extremely high precision. The process is arduous, but physicists can calculate a good deal of the interactions simply by hand. Thats not the case with contributions from particles bound together by the strong force called hadrons, which represent the majority of uncertainty in the calculation of the muons anomalous magnetic moment.
Gluons, the particles that mediate the strong force, are described by the rules of quantum chromodynamics, or QCD. Unlike photons in QED, gluons can interact with one another. Trying to calculate QCD processes by hand is effectively impossible, because the self-interacting gluons throw everything out of whack.
The reason why we need a collaborative effort is because the hadronic corrections cannot be calculated from first principle QCD on a blackboard, says El-Khadra.
There are two main types of hadronic corrections: vacuum polarization corrections and light by light corrections. In vacuum polarization, the muon emits a virtual photon, which decays into a quark and antiquark. These quarks and antiquarks exchange gluons, turning into a frothing blob of hadronic matter such as pions and kaons. Finally, the virtual blob of hadronic matter ends when a quark and antiquark annihilate back into a virtual photon, which is finally absorbed by the muon.
Light by light contributions are perhaps some of the strangest. From the outside, it looks as if two virtual photons are emitted by a muon, interact, and are then absorbed. Whats going on here?
When we look around us the reason why we can see very well is because photonsto a large degreedon't interact with each other, says Christoph Lehner, a physicist at Brookhaven National Lab and cofounder of the Theory Initiative.
But if the two virtual photons get caught in a quark loop, each converting to a virtual quark and virtual antiquark, they can form a blob of hadronic matter. If the virtual quarks and virtual antiquarks annihilate back into virtual photons, the two will appear to have bounced off of one another, interacting in a forbidden way.
Traditionally, hadronic corrections to were calculated using so-called dispersion relations. Physicists modeling the virtual blob of hadronic matter would turn to experiments where real blobs of hadronic matter were created. Real blobs are produced in experiments where electrons collide with positrons, creating a spray of hadronic matter. Experiments like BaBar, KLOE and now Belle II all provide this kind of data, which physicists have scoured to better understand the virtual blobs.
Recently, another method for calculating messy hadronic blobs has become viable, thanks to increasingly powerful computers and improved algorithms. Lattice QCD is a method for essentially simulating the blob from the ground up. Physicists write in the properties of the particles and the forces that govern them, set up a giant sandbox (a lattice) that the system can evolve in, and let it run. Lattice QCD is hugely computationally intensiveto produce a precise simulation, supercomputers have to calculate all of the gluon interchanges, a task that was impossible by hand.
Because its a simulation of the real world from first principles, its in that sense very similar to an experiment, according to Lehner.
One benefit is that physicists can be confident that their approach provides an answer to the question. The downsides, as in any experiment, are systematic errorsand the amount of resources required. Finding computer time is easier said than done, but at the end of the day, lattice QCD is approaching the precision of the dispersion relation method.
In February, a lattice QCD group claimed to have a result for hadronic contributions in serious conflict with the predictions of dispersive relations. Almost immediately, a flurry of other publications discussing and challenging the result followed. The June paper from the Theory Initiative does not address the potential inconsistency, but lattice QCD researchers are hard at work trying to replicate the result.
At the end of the day, when the experimentalists finish analyzing the data from the Muon g-2 experiment, theyll compare against the theoretical value to see if theres still a significant discrepancy. The hope, for many, is that they continue to disagree, opening a window for new physics.
Editor's note: The sentence"That's a difference of less than 3 parts per million, for those keeping score at home," has been updated to correct the number.
Link:
The many paths of muon math | symmetry magazine - Symmetry magazine
Sumit Das to Deliver 2019-20 A&S Distinguished Professor Lecture on ‘Deconstructing Space-Time’ – UKNow
LEXINGTON, Ky. (Oct. 20, 2020) Sumit R. Das, the Jack and Linda Gill Professor in the University of Kentucky Department of Physics and Astronomy, is serving as the 2019-20 UK College of Arts and Sciences Distinguished Professor and will deliver the annual Distinguished Professor Lecture next week.
The lecture, titled Deconstructing Space-Time, will be held 7-8 p.m. Thursday, Oct. 29, on Zoom.
Developments in theoretical physics over the past couple of decades have led to a set of ideas that "space" is not a fundamental notion, but arises as an emergent concept from more abstract entities. This view has led to remarkable progress in reconciling the laws of gravity with the principles of quantum mechanics and has shed valuable light on puzzles related to black holes. This talk will discuss the historical origins of some of these ideas and recent results that have enriched our understanding of the fundamental laws of nature.
Das received his bachelor's and master's degrees in physics from the University of Calcuttaand his doctorate from the University of Chicago in 1984. After postdoctoral positions at Fermi National Accelerator Laboratories and California Institute of Technology, he joined the faculty of Tata Institute of Fundamental Research inMumbai in 1987. In 2002 he moved to the University of Kentucky as a full professor. He served as the department chair from 2013 to 2017. Over the years he has held visiting professor positions in several institutions around the world.His research has meandered through several areas of theoretical physics: the theory of strong interactions, string theory, quantum aspects of black holes and aspects of nonequilibrium phenomena. He has published more than 140 research papers, several chapters in books and two encyclopedia articles. He is a recipient of the S.S. Bhatnagar Award and a fellow of the Indian Academy of Sciences.
To register for the lecture, visit https://uky.zoom.us/webinar/register/WN_cqbe095LQg-WrP4kL6IPmA.
Since 1944, the College of Arts and Sciences has recognized the accomplishments of its faculty in the humanities, social sciences, and natural and mathematical sciences, with the Distinguished Professor Award. The award is the highest professional recognition offered by the college and is bestowed on the basis of three criteria: outstanding research, exceptionally effective teaching and distinguished professional service.
Read this article:
In Waterloo they’re looking for nature’s deepest and weirdest secrets – National Observer
Tim Hsieh, a theoretical physicist, pauses when asked what he studies for a living.
"It's pretty tricky, to be honest," acknowledges Hsieh, a faculty member at the newly created Clay Riddell Centre for Quantum Matter at the Perimeter Institute for Theoretical Physics in Waterloo, Ont.
"It's kind of a different way of thinking about physics. Quantum matter is a very different philosophy."
But there's no hesitation when he talks about the possibilities that may emerge from the brains and blackboards at the centre.
"This is one of the most open-minded places I've ever been."
The centre is the result of a $10-million donation announced this week from the Riddell Family Foundation set up by Clay Riddell, who was a Calgary businessman and philanthropist.
It's the largest single donation since the institute's founding two decades ago. The money will aid Canadian researchers to probe some of the deepest and strangest properties of the world within the atom and, maybe, make breakthroughs toward a next generation of supercomputers or impossibly efficient power grids.
Quantum mechanics is what happens to physics when it gets really, really small, said centre director Rob Myers.
"When you go to the scale of atoms or even smaller, the rules of how the universe works change."
Predictions go from certainties to probabilities. Seemingly unconnected particles affect each other in ways Isaac Newton never dreamed of and that Albert Einstein once called "spooky action at a distance."
Understanding that spooky action is what scientists like Hsieh and others at the new centre are doing. The results, said Myers, will be profound.
Quantum computers will be able to do calculations that would take traditional computers thousands of years. Ultrasensitive quantum sensors could reshape medicine or environmental monitoring.
Quantum cybersecurity could be virtually unhackable. Quantum-based superconductors could transmit electricity without losing any of it.
The institute has already been an integral part of research that brought the world its first images of a black hole.
But the best stuff probably hasn't even been thought of yet, Myers said. Think of how cellphones science fiction a generation ago have changed society.
"We hope the theoretical work we're doing here builds the foundation for the cellphones of the future. (Our scientists) are thinking about the big questions and swinging for the fences."
Hsieh said his work, day to day, isn't that grandiose. He reads others' research and confers with both theoretical and experimental colleagues.
"Also, a lot of daydreaming," he said, "hopefully constructive. It's a very non-linear process. You just keep following your nose and what you think is fundamentally interesting."
The value of places such as the new centre is in bringing people together who are looking at similar phenomena from different angles and letting them work things out, Hsieh said.
"When you bring together a group of people, you have a lot of inspiration from ways of looking at the same material a lot of flow of ideas."
The institute and its new Riddell Centre are one of very few places in the world where this kind of work goes on, he said.
"People (here) have no boundaries and they're very willing to listen to your work," said Hsieh. "When you couple that to this field of quantum matter, you really get a lot of potential for breakthroughs with high, real-world impacts."
This report by The Canadian Press was first published Oct. 16, 2020.
Don't miss out on the latest news
See the rest here:
In Waterloo they're looking for nature's deepest and weirdest secrets - National Observer
Of Science, Philosophy and Revelation – Greater Kashmir
Theoretical physicists tell us that at least 95% of the Universe is dark matter and dark energy, of which we know nothing. The remaining 5% is what we know, and we know it through mathematical calculations, approximations and speculations. In these mathematical calculations, many suppositions have been made, many approximations have been introduced and many a time even unfounded constants have been used by theoretical physicists and mathematicians. Of this 5%, only a negligible portion have we actually seen through telescope.
Again, through the telescope we see what existed in the past. Except for a few cases, nobody knows whether a star that we see in a telescope exists at this time or not. But when it comes to religion bashing, some scientists and those driven by militant-atheist ideology make big claims like heaven and hell do not exist, we couldnt find them anywhere in the Universe, God did not create this Universe etc. Some have gone to the extent of claiming that God does not exist at all. They say things are driven by natural laws. I wonder which laws those which General Theory of Relativity has already shown as being inconsistent, those which contradict each other. Even if we consider everything is driven by exactly these laws who in the first place created these laws, who put them into place, who established them?
Let us talk of matter. What is matter? Nobody knows. No scientist knows. Up to the start of 20th century, it was thought we know everything about matter. Then came Plank and Heisenberg and destroyed all our fantasies. Quantum Mechanics told us that we know nothing of the true nature of matter and we cant know anything. It has been nearly 100 years since Quantum Mechanics came into existence and we havent moved even an inch further. Even today, in the 21st century, we know nothing of the true nature of matter. Gone are the days when we used to say matter means atoms, an atom has proton, neutron and electron; gone even are the days when it was held true that it is all about quarks, electrons, neutrinos & bosons and we know about each of them. Quantum Mechanics told us how ignorant we are. It told us the only thing we know to some extent is interaction of particles and this knowledge of interaction has led to all technology that we see around. The more we know about the Universe, the more we realize how little we know. Encyclopedia of Ignorance also points out to this fact.
At the end of 17th century, Newton introduced the concept of Gravity. At that time, we thought we understood all. Now, three centuries have passed but still no one knows what actually gravity is and what is its cause!
We were told by theoretical physicists that all is controlled by four forcesfour fundamental forces of nature as they had put itgravitational force, electromagnetic force, weak nuclear force and strong nuclear force. But then in the latter part of 20th century, it was said that there are only three forces and now it is being proposed that may be it is only one force and we had understood all incorrectly.
Newtonian Physics told us that Universe is static and it didnt have any starting point, it always existed which directly or indirectly meant no one created this universe. This theory along with Darwinian Theory of Natural Selection made belief in God and religion somewhat incompatible with science. Centuries passed like this but then we realized it was all untrue. Universe had a beginning and seems to have an end too. Einsteins Theory of Relativity clearly implied that the Universe had a beginning and is expanding from the very first moment of its creation (later established by Hubbles observation) but perhaps because of his agnostic beliefs Einstein didnt challenge the Static Universe theory and perhaps because of the same reason he felt disturbed by the very concept of quantum mechanics.
More than a century has passed, the missing links in the concept of Evolution are still missing. This concept and how it is taught is also put to question, its validity under doubt. Some evidences seem to support it, others seem to disprove it. No final conclusion. Then it was suggested we should continue with this theory until a better one comes to fore.
J.W.N. Sullivan has put it aptly, A true scientific theory merely means a successful working hypothesis. It is highly probable that all scientific theories are wrong.
We have famed scientists like Stephen Hawking who made typical militant-atheist type attacks on the concept of God and religion. We have honest Noble Laureate scientists like Einstein who when asked whether he was an atheist, denied that and said I am agnostic. We have incredible Noble Laureate scientists like Heisenberg who vividly said that science and religion are not in conflict with each other, they complement each other. Sir James Jeans also tried to elaborate on the same.
Philosophy: Though philosophy is a separate field of study but here I consider its mention a compulsion. Philosophers from time immemorial have tried to tell us about the meaning this universe carries, about God and about religion. Philosophy relies on imagination. Science relies on observation and experimentation. We must acknowledge the fact that when science has failed to tell us anything about God, religion, the absolute reality and the meaning which this Universe carries how can philosophy (which in front of science doesnt stand anywhere)! When we critically read various philosophies concerning God and religion we realize it is all conjecture. Neither does it have a solid foundation nor does it lead us to conclusive results.
Conclusion: Neither science nor philosophy can lead us to any substantive understanding of God or of religion. It is God and God alone who can truly guide us in this matter. This necessarily implies that it is only and only Revelation that can show us the path.
The author has a PhD from Jamia Millia Islamia, New Delhi and teaches Computer Engineering at Islamic University of Science and Technology, Awantipora.
See the original post here:
Reality Does Not Depend on the Measurer According to New Interpretation of Quantum Mechanics – SciTechDaily
For 100 years scientists have disagreed on how to interpret quantum mechanics. A recent study by Jussi Lindgren and Jukka Liukkonen supports an interpretation that is close to classical scientific principles.
Quantum mechanics arose in the 1920s and since then scientists have disagreed on how best to interpret it. Many interpretations, including the Copenhagen interpretation presented by Niels Bohr and Werner Heisenberg and in particular von Neumann-Wigner interpretation, state that the consciousness of the person conducting the test affects its result. On the other hand, Karl Popper and Albert Einstein thought that an objective reality exists. Erwin Schrdinger put forward the famous thought experiment involving the fate of an unfortunate cat that aimed to describe the imperfections of quantum mechanics.
Photo: Jukka Liukkonen (left) and Jussi Lindgren (right) describe Heisenbergs uncertainty principle. Credit: Aalto University
In their most recent article, Finnish civil servants Jussi Lindgren and Jukka Liukkonen, who study quantum mechanics in their free time, take a look at the uncertainty principle that was developed by Heisenberg in 1927. According to the traditional interpretation of the principle, location and momentum cannot be determined simultaneously to an arbitrary degree of precision, as the person conducting the measurement always affects the values.
However, in their study Lindgren and Liukkonen concluded that the correlation between a location and momentum, i.e. their relationship, is fixed. In other words, reality is an object that does not depend on the person measuring it. Lindgren and Liukkonen utilized stochastic dynamic optimization in their study. In their theorys frame of reference, Heisenbergs uncertainty principle is a manifestation of thermodynamic equilibrium, in which correlations of random variables do not vanish.
But is an explanation really an explanation, if its a vague one? Jussi Lindgren
The results suggest that there is no logical reason for the results to be dependent on the person conducting the measurement. According to our study, there is nothing that suggests that the consciousness of the person would disturb the results or create a certain result or reality, says Jussi Lindgren.
This interpretation supports such interpretations of quantum mechanics that support classical scientific principles.
The interpretation is objective and realistic, and at the same time as simple as possible. We like clarity and prefer to remove all mysticism, says Liukkonen.
The researchers published their last article in December 2019, which also utilized mathematical analysis as a tool to explain quantum mechanics. The method they used was stochastic optimal control theory, which has been used to solve such challenges as how to send a rocket from the Earth to the Moon.
Following Occams razor, the law of parsimony named after William of Ockham, the researchers have now chosen the simplest explanation from those that fit.
We study quantum mechanics as a statistical theory. The mathematical tool is clear, but some might think it is a boring one. But is an explanation really an explanation, if its a vague one? asks Lindgren.
In addition to the study of quantum mechanics, Lindgren and Liukkonen have many other things in common: they were both members of the same maths club at Kuopio Lyceum High School, they both have done post-graduate research, and both have careers as civil servants. Liukkonen has already finished his PhD dissertation on endoscopic ultrasound on joints and now works as an inspector at Radiation and Nuclear Safety Authority.
Physics is a great hobby for a civil servant. Together we have agonized over how the interpretations of quantum mechanics make no sense, says Liukkonen.
Lindgrens dissertation currently consists of various mathematical articles trying to explain quantum mechanics. He works full-time as a ministerial adviser at Prime Ministers Office where he has been negotiating such issues as the EUs recovery plan. A decade ago, he also participated in negotiations on Greeces loan guarantees, as a junior official.
Lindgren and Liukkonens idea of a paradise is a festival conference that would combine short films with lectures on quantum physics.
Physicists and artists could find new ways to work together after all, both areas are manifestations of creativity, says Lindgren.
Reference: The Heisenberg Uncertainty Principle as an Endogenous Equilibrium Property of Stochastic Optimal Control Systems in Quantum Mechanics by Jussi Lindgren and Jukka Liukkonen, 17 September 2020, Symmetry.DOI: 10.3390/sym12091533
Read the original:
Max Planck and the Birth of Quantum Mechanics – SciTechDaily
From left to right: Walther Nernst, Albert Einstein, Max Planck, Robert Andrews Millikan, and Max von Laue at a dinner given by von Laue on November 12, 1931, in Berlin.
In the early evening of Sunday, October 7, 1900120 years agoMax Planck found the functional form of the curve that we now know as the Planck distribution of black-body radiation. By my account, it was the birthdate of quantum mechanics.
A few hours earlier Hermann Rubens and his wife had visited the Plancks. This being a Sunday, they probably enjoyed coffee and cake together. Rubens was the experimental professor of physics at Humboldt University in Berlin where Planck was the theoretical one. Rubens and his collaborator, Ferdinand Kurlbaum, had recently managed to measure the power emitted by a black body as a function of temperature at the unusually long wavelength of 51 microns. They had used multiple reflections from rock salt to filter a narrow band of the spectrum. Working at 51 microns, they measured the low temperature limit and the highest temperatures within the experimental reach of their oven. The remarkable result was that at low frequencies, in the classical regime, the results did not fit the predictions of Wilhelm Wien. Rubens told Planck that for small frequencies the measured spectral density was linear with temperature.
Planck was intrigued. As soon as the gathering ended, he set to work. His interest in the data was profound. That evening he figured out the shape of the curve, with its peculiar denominator that in the limit of low frequency showed the appropriate experimental behaviorlinear with temperature.
The anecdote, as referred by Abraham Pais in his book Subtle is the Lord, states that Planck mailed a postcard to Rubens with the function that very evening, so that Rubens would get it first thing in the morning (the post would have been delivered and set on his desk by the time he arrived at his office in the university). Rubens probably asked Planck that very same morning: Why is it this shape?
The presentation of new data, followed by Plancks function, was on October 17. The function fit the data, both at the low temperature and high temperature limits. Planck had been interested on the black body spectrum for a long time. He understood thermodynamics and classical electrodynamics. But it was the high-quality data of Rubens that drove his mind to find a solution. It took him a few months, and on Dec. 14 he presented the derivation of his theory where, on an act of desperation, he introduced the quantum of energy: the beginning of quantum mechanics.
In memory of Mario Molina.
This historical note was written by JQI Fellow Luis Orozco.
Read the original here:
Max Planck and the Birth of Quantum Mechanics - SciTechDaily
Bringing the promise of quantum computing to nuclear physics – MSUToday
Quantum mechanics, the physics of atoms and subatomic particles, can be strange, especially compared to the everyday physics of Isaac Newtons falling apples. But this unusual science is enabling researchers to develop new ideas and tools, including quantum computers, that can help demystify the quantum realm and solve complex everyday problems.
Thats the goal behind a new U.S. Department of Energy Office of Science (DOE-SC) grant, awarded to Michigan State University (MSU) researchers, led by physicists at Facility for Rare Isotope Beams (FRIB). Working with Los Alamos National Laboratory, the team is developing algorithms essentially programming instructions for quantum computers to help these machines address problems that are difficult for conventional computers. For example, problems like explaining the fundamental quantum science that keeps an atomic nucleus from falling apart.
The $750,000 award, provided by the Office of Nuclear Physics within DOE-SC, is the latest in a growing list of grants supporting MSU researchers developing new quantum theories and technology.
The aim is to improve the efficiency and scalability of quantum simulation algorithms, thereby providing new insights on their applicability for future studies of nuclei and nuclear matter, said principal investigator Morten Hjorth-Jensen, an FRIB researcher who is also a professor in MSUs Department of Physics and Astronomy and a professor of physics at the University of Oslo in Norway.
Morten Hjorth-Jensen (Credit: Hilde Lynnebakken)
Although this grant focuses on nuclear physics, the algorithms it yields could benefit other fields looking to use quantum computings promise to more rapidly solve complicated problems. This includes scientific disciplines such as chemistry and materials science, but also areas such as banking, logistics, and data analytics.
There is a lot of potential for transferring what we are developing into other fields, Hjorth-Jensen said. Hopefully, our results will lead to an increased interest in theoretical and experimentaldevelopments of quantum information technologies. All the algorithms developed as part of this work will be publicly available, he added.
What makes quantum computers attractive tools for these applications is a freedom afforded by quantum mechanics.
Classical computers are constrained to a binary system of zeros and ones with transistors that are either off or on. The restrictions on quantum computers are looser.
Instead of transistors, quantum computers use technology called qubits (pronounced q-bits) that can be both on and off at the same time. Not somewhere in between, but in both opposite states at once.
Combined with the proper algorithms, this freedom enables quantum computers to run certain calculations much faster than their classical counterparts. The type of calculations, for instance, capable of helping scientists explain precisely how swarms of elementary particles known as quarks and gluons hold atomic nuclei together.
"It is really hard to do those problems, said Huey-Wen Lin, a co-investigator on the grant. I dont see a way to solve them any time soon with classical computers.
Huey-Wen Lin
Lin is an assistant professor in the Department of Physics and Astronomy and the Department of Computational Mathematics, Science and Engineering at MSU.
She added that quantum computers wont solve these problems immediately, either. But the timescales could be measured in years rather than careers.
Hjorth-Jensen believes this project will also help accelerate MSUs collaborations in quantum computing. Formally, this grant supports a collaboration of eight MSU researchers and staff scientist Patrick Coles at Los Alamos National Laboratory.
But Hjorth-Jensen hopes the project will spark more discussions and forge deeper connections with the growing community of quantum experts across campus and prepare the next generation of researchers. The grant will also open up new opportunities in quantum computing training for MSU students who are studying in the nations top-ranked nuclear physics graduate program.
The grant, titled From Quarks to Stars: A Quantum Computing Approach to the Nuclear Many-Body Problem, was awarded as part of Quantum Horizons: Quantum Information Systems Research and Innovation for Nuclear Science," a funding opportunity issued by DOE-SC.
Hjorth-Jensen and Lin are joined on this grant by their MSU colleagues Alexei Bazavov and Matthew Hirn from the Department of Computational Mathematics, Science and Engineering; Scott Bogner, Heiko Hergert, Dean Lee and Andrea Shindler from FRIB, and the Department of Physics and Astronomy. Hirn is also an assistant professor in the Department of Mathematics.
MSU is establishing FRIB as a new user facility for the Office of Nuclear Physics in the U.S. Department of Energy Office of Science. Under construction on campus and operated by MSU, FRIB will enable scientists to make discoveries about the properties of rare isotopes in order to better understand the physics of nuclei, nuclear astrophysics, fundamental interactions, and applications for society, including in medicine, homeland security, and industry.
The U.S. Department of Energy Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of todays most pressing challenges. For more information, visit energy.gov/science.
Read the original post:
Bringing the promise of quantum computing to nuclear physics - MSUToday
Could Schrdinger’s cat exist in real life? Our research may soon provide the answer – The Conversation AU
Have you ever been in more than one place at the same time? If youre much bigger than an atom, the answer will be no.
But atoms and particles are governed by the rules of quantum mechanics, in which several different possible situations can coexist at once.
Quantum systems are ruled by whats called a wave function: a mathematical object that describes the probabilities of these different possible situations.
And these different possibilities can coexist in the wave function as what is called a superposition of different states. For example, a particle existing in several different places at once is what we call spatial superposition.
Its only when a measurement is carried out that the wave function collapses and the system ends up in one definite state.
Generally, quantum mechanics applies to the tiny world of atoms and particles. The jury is still out on what it means for large-scale objects.
In our research, published today in Optica, we propose an experiment that may resolve this thorny question once and for all.
In the 1930s, Austrian physicist Erwin Schrdinger came up with his famous thought experiment about a cat in a box which, according to quantum mechanics, could be alive and dead at the same time.
In it, a cat is placed in a sealed box in which a random quantum event has a 5050 chance of killing it. Until the box is opened and the cat is observed, the cat is both dead and alive at the same time.
In other words, the cat exists as a wave function (with multiple possibilities) before its observed. When its observed, it becomes a definite object.
After much debate, the scientific community at the time reached a consensus with the Copenhagen interpretation. This basically says quantum mechanics can only apply to atoms and molecules, but cant describe much larger objects.
Turns out they were wrong.
In the past two decades or so, physicists have created quantum states in objects made of trillions of atoms large enough to be seen with the naked eye. Although, this has not yet included spatial superposition.
Read more: Experiment shows Einstein's quantum 'spooky action' approaches the human scale
But how does the wave function become a real object?
This is what physicists call the quantum measurement problem. It has puzzled scientists and philosophers for about a century.
If there is a mechanism that removes the potential for quantum superposition from large-scale objects, it would require somehow disturbing the wave function and this would create heat.
If such heat is found, this implies large-scale quantum superposition is impossible. If such heat is ruled out, then its likely nature doesnt mind being quantum at any size.
If the latter is the case, with advancing technology we could put large objects, maybe even sentient beings, into quantum states.
Physicists dont know what a mechanism preventing large-scale quantum superpositions would look like. According to some, its an unknown cosmological field. Others suspect gravity could have something to do with it.
This years Nobel Prize winner for physics, Roger Penrose, thinks it could be a consequence of living beings consciousness.
Read more: 2020 Nobel Prize in physics awarded for work on black holes an astrophysicist explains the trailblazing discoveries
Over the past decade or so, physicists have been feverishly seeking a trace amount of heat which would indicate a disturbance in the wave function.
To find this out, wed need a method that can suppress (as perfectly as is possible) all other sources of excess heat that may get in the way of an accurate measurement.
We would also need to keep an effect called quantum backaction in check, in which the act of observing itself creates heat.
In our research, weve formulated such an experiment, which could reveal whether spatial superposition is be possible for large-scale objects. The best experiments thus far have not been able to achieve this.
Our experiment would use resonators at much higher frequencies than have been used. This would remove the issue of any heat from the fridge itself.
As was the case in previous experiments, we would need to use a fridge at 0.01 degrees kelvin above absolute zero. (Absoloute zero is the lowest temperature theoretically possible).
With this combination of very low temperatures and very high frequencies, vibrations in the resonators undergo a process called Bose condensation.
You can picture this as the resonator becoming so solidly frozen that heat from the fridge cant wiggle it, not even a bit.
We would also use a different measurement strategy that doesnt look at the resonators movement at all, but rather the amount of energy it has. This method would strongly suppress backaction heat, too.
Read more: Seven common myths about quantum physics
But how would we do this?
Single particles of light would enter the resonator and bounce back and forth a few million times, absorbing any excess energy. They would eventually leave the resonator, carrying the excess energy away.
By measuring the energy of the light particles coming out, we could determine if there was heat in the resonator.
If heat was present, this would indicate an unknown source (which we didnt control for) had disturbed the wave function. And this would mean its impossible for superposition to happen at a large scale.
The experiment we propose is challenging. Its not the kind of thing you can casually set up on a Sunday afternoon. It may take years of development, millions of dollars and a whole bunch of skilled experimental physicists.
Nonetheless, it could answer one of the most fascinating questions about our reality: is everything quantum? And so, we certainly think its worth the effort.
As for putting a human, or cat, into quantum superposition theres really no way for us to know how this would effect that being.
Luckily, this is a question we dont have to think about, for now.
Read the original here:
A Force From Nothing Used to Control and Manipulate Objects – SciTechDaily
Depiction of the clamping device and how it works. Credit: Jake Pate, UC Merced
A collaboration between researchers from The University of Western Australia and The University of California Merced has provided a new way to measure tiny forces and use them to control objects.
The research, published recently in Nature Physics,was jointly led by Professor Michael Tobar, from UWAs School of Physics, Mathematics and Computing and Chief Investigator at the Australian Research Council Centre of Excellence for Engineered Quantum Systems and Dr. Jacob Pate from the University of Merced.
Professor Tobar said that the result allowed a new way to manipulate and control macroscopic objects in a non-contacting way, allowing enhanced sensitivity without adding loss.
Once thought to be of only academic interest, this tiny force known as the Casimir force is now drawing interest in fields such as metrology (the science of measurement) and sensing.
If you can measure and manipulate the Casimir force on objects, then we gain the ability to improve force sensitivity and reduce mechanical losses, with the potential to strongly impact science and technology, Professor Tobar said.
We have now shown its also possible to use the force to do cool things. But to do that, we need to develop precision technology that allows us control and manipulate objects with this force. Professor Michael Tobar
To understand this, we need to delve into the weirdness of quantum physics. In reality a perfect vacuum does not exist even in empty space at zero temperature, virtual particles, like photons, flicker in and out of existence.
These fluctuations interact with objects placed in vacuum and are actually enhanced in magnitude as temperature is increased, causing a measurable force from nothing otherwise known as the Casimir force.
This is handy because we live at room temperature. We have now shown its also possible to use the force to do cool things.But to do that, we need to develop precision technology that allows us control and manipulate objects with this force.
Professor Tobar said researchers were able to measure the Casimir force and manipulate the objects through a precision microwave photonic cavity, known as a re-entrant cavity, at room-temperature, using a setup with a thin metallic membrane separated from the re-entrant cavity, exquisitely controlled to roughly the width of a grain of dust.
Because of the Casimir force between the objects, the metallic membrane, which flexed back and forth, had its spring-like oscillations significantly modified and was used to manipulate the properties of the membrane and re-entrant cavity system in a unique way, he said.
This allowed orders of magnitudes of improvement in force sensitivity and the ability to control the mechanical state of the membrane.
Reference: Casimir spring and dilution in macroscopic cavity optomechanics by J. M. Pate, M. Goryachev, R. Y. Chiao, J. E. Sharping and M. E. Tobar, 3 August 2020, Nature Physics.DOI: 10.1038/s41567-020-0975-9
View post:
A Force From Nothing Used to Control and Manipulate Objects - SciTechDaily