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Category Archives: Quantum Physics
Posted: October 16, 2019 at 5:33 pm
Shimon Kolkowitz, a University of WisconsinMadison assistant professor of physics, has been selected as one of 22 members of the 2019 class of Packard Fellows for Science and Engineering.
The fellowship, awarded to early-career scientists from across the U.S., provides $875,000 of funding over five years. Kolkowitz will use the funds to develop his research program in ultra-precise atomic clocks, which he will use to investigate such fundamental aspects of physics as the relationship between quantum mechanics and gravity and the nature of dark matter.
Shimon Kolkowitz is the third UWMadison physics professor to be named a Packard Fellow in the 32 years of the award. Photo: Steven Burrows / JILA
These clocks are the most precise instruments that humankind has ever built, Kolkowitz says. Im interested in asking, How does that precision give us access to new physics?
One of the first research areas Kolkowitz plans to explore is a new test of Einsteins general theory of relativity. When first developing the theory, Einstein suggested that people in a closed elevator could not tell the difference between the elevator on Earth under the influence of gravity and the elevator accelerating through space in zero gravity.
Thats called the Einstein equivalence principle, and it is at the heart of general relativity. The predictions of general relativity have been tested in a number of different ways and have always been confirmed, Kolkowitz explains. But the basic question of, Can I tell the difference between acceleration and gravity? has not been directly tested. And I think it will be a lot of fun and really cool to directly realize that thought experiment in my lab.
Atomic clocks keep time by measuring the differences between energy levels of the electrons in atoms. The clocks timekeeping precision is affected by many factors, such as the surrounding environment, the temperature of the atoms, and the type of atom used. The atomic clocks constructed in Kolkowitzs lab are made of strontium atoms that have both been gathered into a small sphere and cooled to just above absolute zero the coldest temperature that can exist by lasers.
Kolkowitzs ultra-precise atomic clock, an ultra-high vacuum containing strontium atoms that are trapped and cooled to 1/1000th of a degree above absolute zero by lasers, will test Einsteins general theory of relativity. Photo: Shimon Kolkowitz
The general theory of relativity says that gravity affects the passage of time, so two atomic clocks at different heights, which experience slight differences in the strength of gravity, will tick at different rates. Currently, that time difference has been observed between two atomic clocks that are about a foot apart in height. A unique feature of Kolkowitzs clock design is that it allows two clocks to exist in the same environment. As a result, in the first set of experiments he plans to conduct, he expects they will be able to measure differences in time due to gravity at centimeter or millimeter height differences.
Next, he wants to measure differences in time between two accelerating clocks that are separated by the same distance this time horizontally instead of vertically to take the effects of gravity out of the equation.
According to the equivalence principle, we should see the same disagreement between the two clocks from the acceleration as from gravity, Kolkowitz says. And thats an effect that has never been observed before.
The Packard Fellowship gives me the freedom to explore research avenues that might not have obvious or immediate applications, but that can inspire the imagination, and that will hopefully lead in unexpected directions.
Kolkowitz admits he is not entirely sure what the implications of these experiments may be. One possibility he is exploring with theoretical physics colleagues is whether related experiments with these quantum-physics-based clocks can complement or improve upon high energy particle physics experiments in the search for new physics, such as the nature of dark matter or dark energy.
These experiments are kind of out there, Kolkowitz says. The Packard Fellowship gives me the freedom to explore research avenues that might not have obvious or immediate applications, but that can inspire the imagination, and that will hopefully lead in unexpected directions.
Professor Kolkowitzs innovative research onprecision metrology with quantum systems is original and highly relevant for quantum information science, says Sridhara Dasu, professor and chair of the physics department at UWMadison. We look forward to his continued success in establishing a flourishing research program in the department.
Kolkowitz is the third UWMadison physics professor to be named a Packard Fellow in the 32 years of the award, after Thad Walker (1992) and Cary Forest (1998). Previously named Packard Fellows include Kolkowitzs former advisor as well as two Nobel laureates.
I feel that Im following in the footsteps of some very impressive people, and thats a real honor for me, Kolkowitz says.
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University’s new supercomputer, Traverse, to aid plasma physics and fusion research – The Daily Princetonian
Posted: at 5:33 pm
Photo Courtesy of Denise Applewhite / Office of Communications
The Universitys High-Performance Computing Research Center (HPCRC) has acquired a new supercomputer, named Traverse, which will aid research at the Universitys Plasma Physics Laboratory (PPPL), as well as other University programs.
The addition joins six other computing clusters: Tiger, Dell, and Perseus, which are the largest and reserved primarily for faculty, as well as Nobel, Adroit, and Tigressdata, which are available to students. All the clusters are housed in a building on the Forrestal campus, about three miles from the main campus.
Supercomputers require high amounts of energy, and HPCRC typically uses 1.8 megawatts of electricity and is equipped with backup generators. The clusters can also overheat, which requires ventilating them with cooled air. The facility is efficient enough to have earned a LEED Gold rating.
Thanos Panagiotopoulos, the chair of the chemical and biological engineering department, said that Traverse will allow Princetons Chemistry in Solution and at Interfaces (CSI) lab to model the interactions of a few hundred molecules at a time.
We do problems involving very large-scale calculations that connect quantum mechanics with the collective properties of water and aqueous solutions, Panagiotopoulos said. The simulations usually last only on the order of a few picoseconds but can help CSI understand the atomistic dynamics of various materials.
Roberto Car, director of CSI and the Ralph W. *31 Dornte Professor in Chemistry at the University, said that his group of researchers now uses a new, more efficient mathematical construction, called a deep neural network, which uses machine learning to compute the classical mechanics forces in any number of arrangements that share the same statistical probability. Researchers derive the interaction potentials from density functional theory, which considers the quantum mechanics of the atoms in their ground states.
Having access to that kind of machine at Princeton will allow us to do this work on our code and experiment with the capabilities offered by this architecture, Car said.
Traverse has a similar architectural structure to Summit, the most powerful supercomputer in the world, housed at Oak Ridge National Laboratory. Traverse is a 1.4-petaflop system, making it capable of 1.4 million billion floating-point calculations per second. It is on the TOP500 list, a ranking of the 500 most powerful supercomputers based on standard tests.
Panagiotopoulos and Car noted that Traverse will soon be overtaken by more powerful supercomputers. Car predicted that exascale systems, which would be capable of a billion billion calculations per second and function 1,000 times faster than petascale ones, will be built in the next few years. He noted that PPPL will likely be able to use technology developed at Oak Ridge.
What sets Traverse apart from the previous HPCRC clusters is its architecture described by Car as a hybrid architecture that consists of CPU [central processing unit] and GPUs [graphics processing units]. The clusters were built by IBM, and the GPUs were supplied by Nvidia, which sells GPUs for many personal computers and gaming systems.
Car said the first exascale supercomputers will share a similar architecture to Traverse, meaning that the work required to adapt the researchers current algorithms to Traverse will remain useful.
Traverse will help PPPL model the movement of plasma in its tokamak NSTX-U, the largest of its kind in the world, to better understand how to control the plasma on a millisecond timescale. PPPL was founded in 1951 and has been working, among other projects, to create a viable fusion reactor potentially capable of generating virtually unlimited energy.
Traverse was financed by the University, and it will be used by graduate students, postdoctoral researchers, and faculty at the University, as well as PPPL, which is managed by the Department of Energy.
Posted: at 5:33 pm
No one ever said science education was easy. Certainly the concepts we teach, like conservation of momentum or quantum mechanics, can be hard to grasp. But what really complicates the endeavor is that were also trying to teach a deeper lesson at the same timeto help students understand the nature of science itself.
All too often, young people get the impression that science is about learning certain laws and then applying them to different situations. After all, thats what we make them do on tests, to show that theyve been doing the work. But thats not it at all. Science is the process of building these concepts through the collection of experimental evidence.
And while Im on it, lets call these concepts what they really arenot laws, but models. Science is all about building and testing models. It's difficult to help students understand that aspect of science when we just give them the models to begin with. Sure, in physics we often include historical or mathematical evidence to support big ideas, but that often isnt enough.
Of course, we cant start from scratch. If students had to build their own models from the ground up, it would be like trying to learn programming by inventing computers. As Isaac Newton is supposed to have said, we stand on the shoulders of giants. We must take models built by others and go from there.
But theres still another challenge in science education that is less often recognized: Students often enter a course with their own unarticulated ideas about how the world works. We call these misconceptions, but its important to realize that these are also models, based on their life experiences, and that they must make sense to the student.
What Id like to suggest is that this actually provides a great way into the adventure of science and an opportunity to meet our objectives as educators. If you can create a situation that challenges students assumptions and produces conceptual conflict, that's a great opportunity for learning.
Heres a fun example that Ive used, on the topic of light rays. I set up a point light source and put a piece of cardboard in front of it. Theres a small pinhole in the cardboard and a white screen behind. What do you expect to see?
No surprise: A light shining through a pinhole makes a dot on the screen. Now Ill ask the students: What if I have TWO light sources with the same single hole?
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Posted: at 5:33 pm
By Chelsea Whyte
L. CALCADA / EUROPEAN SOUTHERN OBSERVATORY / SCIENCE PHOTO LIBRARY
Fancy a trip down a wormhole? We have never been quite sure whether these portals through space-time could exist long enough for anything to travel through. Now calculations suggest they could stick around for a while perhaps as long as the universe itself.
Wormholes are essentially two black holes connected together. Two types could theoretically exist. A non-traversable wormhole is like a room with two doors that can only be used from the outside the doors are black holes through which things could enter, but never escape. These are not very interesting, as any astronaut who is brave enough to venture in wont be able to make it back to tell the story, says Diandian Wang at the University of California, Santa Barbara.
Traversable wormholes are also possible, but up until now we didnt know whether they could exist for long enough for anything to pass through in practice.
For such a wormhole to form, space-time needs to change shape from being like a flat sheet to having holes in it. In classical physics, this cant happen. But the rules of quantum mechanics seem to allow for space-time to spontaneously change shape, although this is likely to only be for very short periods.
Wang has now worked on a scenario involving string theory, in which the fundamental ingredient of reality are tiny strings. If one of these strings breaks, it can create a traversable wormhole. It contains energy, and when it breaks, that energy becomes two black holes at each end of the string, says Wang.
Researchers had shown this was a possibility before, but it seemed the energy would force the two black holes to zoom apart from each other, snapping the wormhole.
Now, Wang and his team have calculated that the curvature of space-time could counteract this acceleration, keeping the black holes static and allowing the throat of the wormhole to remain open.This scenario is extremely unlikely, and becomes even more unlikely the longer the wormhole is and the larger the two black holes are.
This means that a wormhole big enough for a person to travel through is much less likely than one through which light could be sent. Thanks to quantum mechanics, though, the probability of either happening isnt zero.
Wangs team also calculated that, once a traversable wormhole exists, it could remain stable for at least as long as the universe has existed and maybe forever.
Our previous work showed that wormholes can be traversable, says Aron Wall at the University of Cambridge. But we did not describe a process to create the wormhole. He says Wangs calculations show how one could be created from scratch.
Wall points out, however, that Wangs wormholes couldnt be used to time travel or move faster than the speed of light. Were you to travel through one, he says, you would still be confined to moving slower than the speed of light.
Journal reference: Classical and Quantum Gravity, DOI: 10.1088/1361-6382/ab436f
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Posted: at 5:33 pm
The gold tip is moved across the surface of the topological insulator and experiences energy loss only at discrete, quantized energies. This is related to the image potential states that are formed over the conducting surface of the topological insulator. Credit: University of Basel, Departement of Physics
Topological insulators are innovative materials that conduct electricity on the surface, but act as insulators on the inside. Physicists at the University of Basel and the Istanbul Technical University have begun investigating how they react to friction. Their experiment shows that the heat generated through friction is significantly lower than in conventional materials. This is due to a new quantum mechanism, the researchers report in the scientific journal Nature Materials.
Thanks to their unique electrical properties, topological insulators promise many innovations in the electronics and computer industries, as well as in the development of quantum computers. The thin surface layer can conduct electricity almost without resistance, resulting in less heat than traditional materials. This makes them of particular interest for electronic components.
Our measurements clearly show that at certain voltages there is virtually no heat generation caused by electronic friction. Dr. Dilek Yildiz
Furthermore, in topological insulators, the electronic friction i.e. the electron-mediated conversion of electrical energy into heat can be reduced and controlled. Researchers of the University of Basel, the Swiss Nanoscience Institute (SNI) and the Istanbul Technical University have now been able to experimentally verify and demonstrate exactly how the transition from energy to heat through friction behaves a process known as dissipation.
The team headed by Professor Ernst Meyer at the Department of Physics of the University of Basel investigated the effects of friction on the surface of a bismuth telluride topological insulator. The scientists used an atomic force microscope in pendulum mode. Here, the conductive microscope tip made of gold oscillates back and forth just above the two-dimensional surface of the topological insulator. When a voltage is applied to the microscope tip, the movement of the pendulum induces a small electrical current on the surface.
In conventional materials, some of this electrical energy is converted into heat through friction. The result on the conductive surface of the topological insulator looks very different: the loss of energy through the conversion to heat is significantly reduced.
Our measurements clearly show that at certain voltages there is virtually no heat generation caused by electronic friction, explains Dr. Dilek Yildiz, who carried out this work within the SNI Ph.D. School.
The researchers were also able to observe for the first time a new quantum-mechanical dissipation mechanism that occurs only at certain voltages. Under these conditions, the electrons migrate from the tip through an intermediate state into the material similar to the tunneling effect in scanning tunneling microscopes. By regulating the voltage, the scientists were able to influence the dissipation. These measurements confirm the great potential of topological insulators, since electronic friction can be controlled in a targeted manner, adds Meyer.
Reference: Mechanical dissipation via image potential states on a topological insulator surface by D. Yildiz, M. Kisiel, U. Gysin, O. Grl and E. Meyer, 14 October 2019, Nature Materials.DOI: 10.1038/s41563-019-0492-3
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Posted: at 5:33 pm
An elusive hypothetical particle comesin imitation form.
Lurking within a solid crystal is aphenomenon that is mathematically similar to proposed subatomic particlescalled axions, physicist JohannesGooth and colleagues report online October 7 in Nature.
If axions exist as fundamentalparticles, they could constitute a hidden form of matter in the cosmos, darkmatter. Scientists know dark matter exists thanks to its gravitational pull,but they have yet to identify what it is. Axions are one possibility, but no one has found the particles yet (SN: 4/9/18).
Enter the imitators. The axions analogswithin the crystal are a type of quasiparticle, a disturbance in a material thatcan mimic fundamental particles like axions. Quasiparticles result from thecoordinated jostling of electrons within a solid material. Its a bit like how birdsin a flock seem to take on new forms by syncing up their movements.
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Axions were first proposed in thecontext of quantum chromodynamics the theory that explains the behaviors of quarks,tiny particles that are contained, for example, inside protons. Axions andtheir new doppelgngers are mathematically similar but physically totallyunrelated, says theoretical physicist Helen Quinn of SLAC National AcceleratorLaboratory in Menlo Park, Calif., one of the scientists who formulated thetheory behind axions. That means scientists are no closer to solving their darkmatter woes.
Still, the new study reveals for thefirst time that the phenomenon has a life beyond mere equations, inquasiparticle form. Its actually amazing, says Gooth, of the Max Planck Institutefor Chemical Physics of Solids in Dresden, Germany. The idea of axions is avery mathematical concept, in a sense, but it still exists in reality.
In the new study, the researchersstarted with a material that hosts a type of quasiparticle known as a Weyl fermion,which behaves as if massless (SN: 7/16/15).When the material is cooled, Weyl fermions become locked into place, forming acrystal. That results in the density of electrons varying in a regular patternacross the material, like a stationary wave of electric charge, with peaks inthe wave corresponding to more electrons and dips corresponding to fewerelectrons.
Applying parallel electric and magneticfields to the crystal caused the wave to slosh back and forth. That sloshing isthe mathematical equivalent of an axion, the researchers say.
To confirm that the sloshing wasoccurring, the team measured the electric current through the crystal. Thatcurrent grew quickly as the researchers ramped up the electric fields strength,in a way that is a fingerprint of axion quasiparticles.
If the scientists changed the directionof the magnetic field so that it no longer aligned with the electric field, theenhanced growth of the electric current was lost, indicating that the axionquasiparticles went away. This material behaves exactly as you would expect,Gooth says.
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Posted: at 5:33 pm
Shenzhen, home to Chinese tech giants Tencent, Huawei and DJI, is known for warp speed when it comes to new product development whether that be in mobile games, 5G wireless technology, or consumer electronics.
Now the Chinese government wants the southern metropolis, designated the countrys first special economic zone 40 years ago when it was a sleepy fishing village, to focus on the longer term by giving it an added role: fundamental research and development.
Often called Chinas Silicon Valley, the city of 12 million has been named as the location of the countrys fourth major national science center amid the Chinese governments ambitions to become a global technology and innovation powerhouse.
China is very good at the hardware, but basic research is not a simple task, said Jonathan Chee, project director at the Center for Entrepreneurship of the Chinese University of Hong Kong. The most cutting-edge research and technology are in the universities and its not easy to bring the talent together to form a cluster Im worried that the efforts would be too costly.
The science centers, managed by the Chinese Ministry of Science and Technology and the National Development and Reform Commission, include technology parks and government-funded laboratories tasked with undertaking basic research in fields such as nuclear reactions, quantum physics and astrophysics. The three existing science centers are in Beijing to the north, Shanghai on the east coast, and Hefei in central China.
Shenzhen is very innovative in technology applications, but the city is traditionally weak in basic science research, said Guo Wanda, executive vice-president of the Shenzhen-based think tank China Development Institute. Without breakthroughs in technologies, the city will be one step behind other international cities.
Details of the Shenzhen project were unveiled by Chinese authorities in August as government planners looked to major mainland cities to drive regional development amid Chinas ongoing trade and tech war with the US.
Chinese President Xi Jinping has repeatedly called for industry to innovate and become more self-reliant. Self-determination and innovation is the unavoidable path to climb to the worlds top as a leading player in technology, Xi told a group of Chinese scientists last year. We [should] hold innovative development tightly in our own hands. [We have to] put much effort in key areas where we are facing bottlenecks and make breakthroughs as soon as we can.
As a key plank in Chinas many policies to advance basic research, the national science centers are designed to serve the strategic needs of the nation by bringing together high level talent and offering an open research environment, according to the countrys 13th five-year plan.
Large-scale technology infrastructure and national labs are expected to be built in Shenzhen, especially in the fields of biological science, cyberspace and materials science, said Guo.
Shenzhen already has Chinas first national gene bank and has hosted a national supercomputing center, though the city still ranks well behind Beijing and Shanghai when it comes to government support in basic science, with 90 per cent of the research institutions in the city funded by private enterprises.
For basic science research, it is necessary to have central government support it is a national strategy and needs nationwide effort no matter whether in the US or Japan, said Liu Ruopeng, head of the Shenzhen-based Kuang-Chi Institute of Advanced Technology,a not-for-profit research institute backed by Kuang Chi Group.
Silicon Valley owes its start in large part to Stanford University in Palo Alto, Japans Tsukuba Science City is home to the STEM-focused University of Tsukuba, while Taiwans Hsinchu Science Park has drawn engineering graduates from nearby National Chiao Tung University and National Tsing Hua University.
However, Shenzhen is not known for its institutions of higher education. Shenzhen University, located in the citys Nanshan district, was placed in the 601st to 800th group in terms of global ranking, according to The Times Higher Education World University Rankings.
Beijing, in contrast, boasts two of the countrys top universities, Peking University and Tsinghua, which rank among the top 50 internationally. As of this year, the Chinese capital had also established a cluster of around 90 universities. Elsewhere, Shanghais Fudan University and Shanghai Jiao Tong University and Hefeis University of Science and Technology are all ranked among Chinas top 10 universities.
Shenzhens status as a science center is expected to encourage overseas universities to set up graduate schools and research institutes in the city. The University of Cambridge in the UK and Peking University are in talks about hosting joint programs in Shenzhen while the Shenzhen MSU-BIT University was jointly established by Lomonosov Moscow State University and the Beijing Institute of Technology.
Shenzhen beat more than a dozen rivals including Chengdu in the southwest and the central Chinese cities of Xian and Wuhan, to secure the countrys fourth science center. Industry experts point to a few advantages that enabled Shenzhen to win amid the fierce competition. One was its role as the technology driver in the Greater Bay Area, a central government plan to turn 11 cities in southern China into an international innovation and technology hub to compete globally.
Another advantage was geography. The three current centers are located in north, east and central China respectively. The new center in Shenzhen will help balance the output of national innovation and drive economy transformation in southern China, said Liu.
It is not hard to understand why Chinese cities vie so keenly for such designations.Like in Silicon Valley, Tsukuba and Hsinchu, government support combined with top level universities attract the talent and capital needed to succeed. Shenzhen, too, expects to see new labs, institutions and universities with its new-found national science status, say experts.
The Shanghai Science Center has received funding of 13.8 billion yuan (US$2 billion) from the central government for multiple large-scale scientific facilities, according to a recent report from state media Xinhua. By 2020, the Chinese government plans to invest 30 billion yuan in the three key centers.
By 2018, China had announced 38 large-scale scientific facilities in areas such as physics and astronomy 22 operating and the remainder planned but none are in southern China. Most are co-located within the existing three national science centers.
Shanghai was chosen to host the countrys first national science center in 2016, supported by infrastructure to enable life science, supercomputing and photon research for applications in integrated circuits, artificial intelligence and bio medicine. The second national science center in Hefei is focused on information technology, energy, health and the environment, and will conduct research in areas such as quantum communications, nuclear fusion, smog prevention and cancer treatment.
The nations third facility, to be operating in the capital of Beijing by 2020, will focus on physical science, space science and geoscience.
Shenzhens designation as a national science center may be new but the citys planners have had their eyes on the prize for a while. In January 2018, the city government proposed a national science and technology center and laid out an ambitious proposal called Ten Plans that entailed 10 scientific and technology infrastructure projects, 10 overseas innovation centers and 10 manufacturing innovation centers.
There is even a plan to establish 10 laboratories backed by Nobel Prize-winning scientists, with blue LED inventor and 2014 Nobel laureate in physics Shuji Nakamura and 2005 laureate in chemistry Robert Grubbs already signed up.
We cannot expect to make a profit from basic science research as quick as technology applications, said Guo. We have to keep investing and be patient.
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Posted: August 6, 2017 at 3:40 am
Major Grant From National Science Foundation Funds Dos Santos Study of Interacting Quantum Systems
How can transitions between different states of matterfor instance, liquids, gasses and solidsbe harnessed to create new kinds of matter for novel technologies? This is the focus of new research by Dr. Lea Ferreira dos Santos, professor of physics at Stern College for Women, whose project, Physics of Interacting Quantum Systems with Phase Transitions, has been funded by a three-year $190,000 grant from the National Science Foundations (NSF) Division of Materials Research.
Dr. Lea Ferreira dos Santos
We are all very well familiar with thermal phase transitions, said dos Santos. The best example is the transition from water to ice. In the liquid phase, the molecules move freely. As the water is cooled, the molecules slow down and begin to arrange themselves into a lattice structure, eventually resulting in the solid phase.
At absolute zero temperature, according to the laws of classical physics (that is, the laws that describe large objects, like human beings), molecules would stop moving and the phase transition would stabilize. However, at low temperatures, classical physics is no longer valid and quantum physics takes over. According to the laws of quantum physics, phase transitions can happen even at the absolute zero temperature. These are known as quantum phase transitions. This NSF grant will help in trying to identify and characterize these transitions.
Although seemingly esoteric, this research can have important real-world applications: For example, a specific phase may be associated with good or bad conduction of energy or electricity. New phases of matter are critical components of emerging technologies and may revolutionize how we use and produce energy, may lead to new electronic devices and may constitute the building blocks of quantum computers. The potential economic and social impact of the discovery of novel phases of matter is immense.
For dos Santos, this is part of what makes the study of physics endlessly intriguing. After so many years studying the subject, I am still fascinated by quantum mechanics. As Nobel Laureate Richard Feynman once said: Nobody understands it. However, over the years, we have been learning how to control and make use of its properties. Through this practical process, we may eventually unveil also its fundamental mysteries. I get a thrill every time I manage to put a couple of pieces of the big puzzle together.
Another welcome result is that this research, as stated in the proposals abstract, will also foster the participation of women in physics and improve the educational infrastructure at the Stern College for Women of Yeshiva University by offering new research opportunities and training in core areas of physics and in computational methods. In one of the projectsrelated to this research dos Santos will be working with three of her former students, who are now physics teachers in high schools for girls, to create a webpage designed for posting computer programs from courses and research findings that will contribute to the integration of teaching and research at other undergraduate institutions.
Posted: at 3:40 am
MORE than 20 years have passed since Pan Jianwei was first astonished by the quantum world. Pondering the strange micro world has carved deep lines in the quantum physicists forehead.
People still dont fully understand a phenomenon such as quantum superposition and quantum entanglement, but Pan is shining some light in the field, manipulating microscopic particles and applying the magical quantum characters to develop quantum cryptography and quantum computing.
The worlds first quantum satellite, Quantum Experiments at Space Scale, launched by China in 2016, has realized the distribution of entangled photon pairs over 1,200 kilometers. It has proved that quantum entanglement, described by Albert Einstein as a spooky action, still exists at such a distance.
As the satellites lead scientist, Pan has a greater goal: to test quantum entanglement between Earth and the moon at a distance over 300,000km, which may help research on gravity and the structure of spacetime.
Pan is a science legend. When his co-authored article about the first quantum teleportation was selected by academic journal Nature as one of the 21 classic papers for physics over the past century, he was only 29 years old. When he was appointed a professor of the University of Science and Technology of China, he was 31. When he was elected an academician of the Chinese Academy of Sciences, he was 41, the youngest academician at that time. When he won the first prize of National Natural Science, he was 45.
The star scientist and media celebrity says science should be in the spotlight rather than scientists.
Born on March 11, 1970 in Dongyang City, east Chinas Zhejiang Province, Pan was an excellent student and a playful boy. He went to study in the University of Science and Technology of China in Hefei City in 1987, where academic competition was fierce.
Wu Jian, Pans classmate in university and now a scientist in Chinas Dark Matter Particle Explorer Satellite project, recalls that he once gave Pan an ugly haircut, but he was not angry. Pan was happy-go-lucky.
In 1990, Pan first came into contact with quantum mechanics, which totally confused him. How can there be such a phenomenon as quantum superposition? Its like a person being in Shanghai and Beijing at the same time.
Pan almost failed in the midterm exam on quantum mechanics.
Desperately trying to figure it out, Pan chose quantum mechanics as his research direction and hes still entangled with it. He realized all the theories about quantum physics had to be tested in experiments. However, China lacked the conditions to do such experiments in the 1990s.
After graduation in 1996, Pan went to Austria to do his PhD at the University of Innsbruck, studying with Anton Zeilinger, a world-renowned quantum physicist.
When Pan came to me as a young student, he was a theoretical physicist. He had not done any experiments before. But I very soon realized he had the gift for doing experiments, Zeilinger said.
I assigned him to do the experiment on teleportation with a group, a very complicated experiment. He accepted it and immediately got started.
He was full of enthusiasm. Soon he was the leading person in the experiment. When there was a problem, he was never discouraged. He always saw it as motivation to do something that had not been done before, Zeilinger says.
He was optimistic, always found solutions to problems, and always wanted to work to find something new, says Zeilinger.
He always got along with his colleagues. Now he is a global leader in the field of quantum physics. Im very proud of him, said Zeilinger. I encouraged him to go back to China. Because I could see there was a big opportunity for him in China.
After mastering advanced quantum technology, Pan returned to the University of Science and Technology of China in 2001 to establish a quantum physics and quantum information laboratory, hoping China could quickly catch up with the pace of development in the emerging field of quantum technology.
In order to make breakthroughs in quantum information research, the lab needed scientists with different academic backgrounds.
Pan sent his students to study in Germany, Britain, the United States, Switzerland and Austria to obtain the most advanced knowledge in specialties such as cold atoms, precision measurement and multiphoton entanglement manipulation.
So far, Pan and his team have published about 200 articles in authoritative academic journals including Science, Nature and Physical Review Letters, indicating that China is at the global forefront of quantum communication.
In experiments, there is inevitably frustration. But Pan says they need patience and the key is to have fun in the process. Pursuing the secrets of the quantum physics brings me calm and peace. Its like walking on the lawn in the spring sunshine, he said.
A fan of classical music, Pan says music and science both give him tranquility and happiness. In college, he read the essays of Einstein. For me, Einsteins essays are the most profound and beautiful sound of nature, he said.
The research of quantum physics has an impact on my personality and thoughts. Quantum mechanics tells me its very hard to define right and wrong, good and bad. It makes me tolerant.
He also takes part in many activities to promote science in China. Development driven by innovation is one of Chinas core strategies. Building an innovation-oriented country requires nurturing the publics interest in science, Pan said.
He believes China can catch up with Japan in about two decades in the field of science and technology, as long as the research funds are allocated and used by the best Chinese scientists properly.
The experiments on the QUESS satellite are the most important scientific research in my life, said Pan.
However, the quantum world remains mysterious. Will the spooky action that confused even Einstein extend in space without limit?
In theory, this bizarre connection can exist over any distance, but we think quantum entanglement might be affected by gravity. The different models need to be tested at a longer distance, and the boundary between quantum physics and the theory of relativity and study the structure of spacetime and gravity should be explored, Pan said.
Originally posted here:
Posted: July 17, 2017 at 4:40 am
Every time physicists find a new particle, the Standard Model gets one step closer to becoming a Super Model.
There's always talk of whether the new arrival fits in, or stands out, or matches the model's predictions. Everything gets related back to this "Bible of quantum physics".
The Standard Model isn't mystical, however. It's purely, beautifully mathematical.
Yet for all its predictive power, it's not perfect it can't explain gravity, dark matter or dark energy. The real goal of particle-smashing physicists is to break it.
Only by finding new particles that weren't predicted by the Standard Model, and can't fit inside it, will we move to a new and improved model one that doesn't have big gaps where gravity and the dark parts of physics should be.
Forty years ago scientists pulled everything they knew about quantum physics into one massive equation the Standard Model of particle physics.
If you can follow the maths, the Standard Model is a stunning piece of work. It's like a how-to guide for the particles and forces that operate at the tiny quantum scale including all the atoms that makes up people, plants, planets and stars.
(Luckily for the non-physicists among us, it also comes in handy table form and our handy video above.)
The really big deal with the Standard Model is that it didn't just describe particles that were already known, like the electron and quarks that make up atoms.
It did something much more important it predicted some new particles too, including the Higgs boson.
Testing predictions is at the heart of science, and every one of the particles that the Standard Model predicted has since been discovered. The Higgs was the last to be found, in 2012.
That ability to predict and explain every aspect of the quantum world makes the Standard Model a bit of a superstar.
But while it's undeniably brilliant, no one has ever pretended the Standard Model is perfect.
The most obvious flaw in the Standard Model was there from the beginning it could never account for gravity, the force that rules at the macro scale. That's not the Standard Model's fault; quantum theory and Einstein's gravitational theory just don't work together.
But gravity's not the only thing missing from the model.
The Standard Model can't account for the dark matter and dark energy that make up a cool 95 per cent of the universe either.
And most bizarre of all, it comes right out and says that universe shouldn't exist at least not the way it is. The Model predicts that matter and antimatter should have been produced in equal amounts at the birth of the universe and annihilated immediately thereafter, leaving one enormous sea of light.
Thankfully that hasn't exactly gone to plan either; there's matter all over the place, including little old you and me.
Some of the Standard Model's other shortcomings are on a much less grand and galactic scale.
One of the best-known problems is that it predicts that one family of particles neutrinos should have zero mass. But as the recipients of the 2015 Nobel Prize in Physics can attest, these ridiculously small particles that travel at near light speed have very tiny, but not zero, masses.
Far from being considered a failure for its shortcomings, the Standard Model has always been appreciated by physicists for what it is: a great start to understanding and possibly unifying all of physics.
And in the decades since it appeared, theoretical physicists have thrown up a pile of possible additions to the Model, trying to account for the things it can't explain.
These mostly involve new particles that are much heavier than the known quarks, leptons and bosons. In supersymmetry, the best known 'upgrade' to the model, every particle has a much heavier partner, called a sparticle, which helps patch the current gaps.
Theories are great, but if we want to find out which, if any, of the various upgrades to the Standard Model are right, we really need to find new particles. And that's where particle accelerators come in.
The Higgs boson was found at the Large Hadron Collider in 2012. With higher energy collisions heavier particles could also be discovered.
The Higgs boson was found at the Large Hadron Collider in 2012. With higher energy collisions heavier particles could also be discovered.
Particle accelerators smash together tiny bits of matter everything from electrons to whole atoms at almost light speed. When that happens, the energy of the collision can be converted into matter. (Einstein's E=mc2 tells us that mass and energy are two sides of the same deal).
And if there's enough energy it can form a heavier particle than we've ever observed.
Heavy particles made in colliders are generally unstable they only exist for an incredibly short time before breaking down into lighter, more stable bits. But those telltale leftovers are exactly the thing physicists look for in particle accelerator experiments all over the world.
So far, new particles haven't been able to 'break' the Standard Model; they just keep opening new chapters of it.
Knowing the mass and energy of these particles will favour some of the new theoretical additions, and knock others out of contention.
The more new particles we find, the narrower the field for refinements to the model.
Any new, heavy particles that are found will result in some new characters in the Standard Model equation, and the beginnings of an extra row or column in the accompanying table. This 'Standard Model Plus' could account for the mass of neutrinos, the antimatter/matter issue, dark matter and dark energy.
But accounting for gravity won't happen without shifting to a new theory altogether one that accounts for all known particles and phenomena as well as the current model does, but that can work with gravity as well.
And theories of quantum gravity won't be validated by particle accelerators any time soon. The energies required to test them are well beyond the range of even the very biggest atom smashers.
For now, a grand unified theory of the universe that ties in quantum and gravitational scales appears to be out of reach. If we ever find it, we'll be in serious Super Model territory.
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