Category Archives: Quantum Physics

Prestigious NSF fellowships awarded to 43 graduate students … – University of Colorado Boulder

Students from across campus have received Graduate Research Fellowships, a prestigious award that recognizes and supports outstanding students in a wide variety of science-related disciplines

The National Science Foundation has awarded 43 University of Colorado Boulder students with the prestigious graduate research fellowship, the federal agencyannounced earlier this month.

The Graduate Research Fellowship Program (GRFP) recognizes outstanding graduate students from across the country in science, technology, engineering and mathematics (STEM) fields, paving the way for their continued work exploring some of the most complex and pressing issues of our time.

This years recipients of the five-year fellowship represent a wide swath of disciplines, spanning quantum physics to ecology. Each GRFP recipient will receive three years of financial support, including an annual stipend of $37,000, as well as professional development and research opportunities.

Of those 43 winners, which places the university in the top fifteen nationwide in terms of number awarded, 60% participated in a workshop or information session organized by the Graduate School, in partnership with the College of Arts and Sciences and the College of Engineering and Applied Sciences. These included specialized writing workshops, coaching sessions and general informational sessions about applying for the GRFP.

"Our continued extraordinary performance among the nations top graduate schools in securing NSF GRFPs is not only a testament to our outstanding graduate students at CU, but also the Graduate Schools approach to cultivating talent with our campus partners and tremendously supportive faculty, said E. Scott Adler, dean of the Graduate School and the vice provost for graduate affairs. We are very proud of the students who have been recognized by this highly competitive program.

This years recipients include:

In addition to the fellowship award winners, 15 students were recognized with an honorable mention. Eleven alumni were also recognized.

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Prestigious NSF fellowships awarded to 43 graduate students ... - University of Colorado Boulder

India’s Minister of Science visits Imperial to strengthen research links – Imperial College London

Indias Minister of Science and Technology Dr Jitendra Singh visited Imperial to meet researchers and students and strengthen ties with India.

The Minister, accompanied byProfessor Ajay Kumar Sood, Principle Scientific Advisor to the Government of India, and other scientists and officials,visited Imperials labs and heard about Imperial's growing research collaborations with India.

The Minister also met with some of Imperial's Indian students and scholars and encouraged them to reach their potential. He also highlighted the rapid progress science in India was making in a number of fields and the growth of Indian startups.

Professor Mary Ryan, Vice Provost (Research and Enterprise) at Imperial College London, said:Wereincredibly proud of our longstanding connections with India.

"We are privileged to host just over 800 talented and highly entrepreneurial students from India.Imperial is also home to a thriving community of researchers and staff with connections to India.

"Our academics collaborate with a range of partners in India, as well as our incredible alumni community, to tackle shared health and climate challenges such as the transition to clean energy, antimicrobial resistance, and infectious disease."

During the visit Imperial announced that it was creating a new scholarship programme for Indian Masters students.

The'Future Leaders Scholarship' programmewill support 30 students over the next three years with half of the scholarships reserved for female scholars. The scholarships will be for students inMSc programmes across Imperial's Faculties of Engineering, Natural Sciences, Medicine and the Business School.

Professor Peter Haynes, Vice-Provost (Education and Student Experience) at Imperial, said: It is a real priority for Imperial to continue tofacilitateand support two-way mobility between India and the UK.

"I hope that weare able towelcome even more students from India in the future and I amvery pleasedto announce that Imperial is investing just over 400,000 in scholarships for the future STEM-B leaders of India.The investment will see the launch of 30 merit-based scholarships over the next three years, with the first application round opening next academic year.

At least 50 per cent of these prestigious Future Leaders scholarships will be reserved for female scholars.I hope that we can continue to work together to build upon our success and that Imperial can be at the fore of supporting UK-India partnerships in the coming decade.

Imperial also announced a new partnership with Chevening for scholars from India. Funding will be available forscholars who demonstrate the greatest potential to become leaders, decision-makers and opinion-formers in India. The Chevening scholarship award will support academic fees and provide a monthly stipend.

TheScience Ministervisited Imperials Carbon Capture Pilot Plant to see how Imperial students aretraining to become the next generation of chemical engineers.

He also saw a demonstration of the latest imaging from the Mars Rover at the Data Science Institute by Professor Sanjeev Gupta.

The Minister then visited Imperials Hydrodynamics lab for a demonstration of the wave tank byProfessor Washington Ochieng and Professor Graham Hughes.

Imperial has longstanding and successful links with India - and is committed to expanding and strengthening partnerships with the country.

Imperial andthe Indian Institute of Science (IISc), Bangalore launched an ambitious partnership in research and education.

The joint seed fund with IISc has already enabled exchange mobility this academic year, with partners spending time in each others labs to explore topics as diverse as bio-acoustics, air pollutants and quantum physics.

Imperials School of Public Health has been collaborating with the Indian Council of Medical Research (ICMR)in support of Indias COVID-19 response. Academics from theJameel InstituteandMRC Centre for Global Infectious Disease Analysis, including Professor Katharina Hauckand Professor Nimalan Arinaminpathy,have supported scientists within the ICMR, toperform modelling analysis to address key questions faced by public health authorities in the country. For example, early in Indias vaccination drive against COVID-19 the largest in the world Imperialcollaborated with the ICMR to provide modelling analysis informing the prioritisation of risk groups.

A major focus of ProfessorArinaminpathy teams research is in the control of human tuberculosis (TB) in high-burden countries. They work closely with India's National Tuberculosis Elimination Programme, contributing mathematical models to help inform intervention planning to meet India's ambitious goals for TB elimination.

Earlier this year Imperial welcomed the Indian High Commissioner tothe College to discuss deepening ties with the country.

Last year Imperial hosted the former Principal Scientific Advisor, Prof Vijay Raghavan and his UK counterpart, Sir Patrick Vallance, at an event to discuss the role of science and innovation partnerships in driving the India-UK Roadmap and creating healthier, resilient societies.

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India's Minister of Science visits Imperial to strengthen research links - Imperial College London

Newly observed effect makes atoms transparent to certain frequencies of light – Phys.org

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A newly discovered phenomenon dubbed "collectively induced transparency" (CIT) causes groups of atoms to abruptly stop reflecting light at specific frequencies.

CIT was discovered by confining ytterbium atoms inside an optical cavityessentially, a tiny box for lightand blasting them with a laser. Although the laser's light will bounce off the atoms up to a point, as the frequency of the light is adjusted, a transparency window appears in which the light simply passes through the cavity unimpeded.

"We never knew this transparency window existed," says Caltech's Andrei Faraon (BS '04), William L. Valentine Professor of Applied Physics and Electrical Engineering, and co-corresponding author of a paper on the discovery that was published on April 26 in the journal Nature. "Our research has primarily become a journey to find out why."

An analysis of the transparency window points to it being the result of interactions in the cavity between groups of atoms and light. This phenomenon is akin to destructive interference, in which waves from two or more sources can cancel one another out. The groups of atoms continually absorb and re-emit light, which generally results in the reflection of the laser's light. However, at the CIT frequency, there is a balance created by the re-emitted light from each of the atoms in a group, resulting in a drop in reflection.

"An ensemble of atoms strongly coupled to the same optical field can lead to unexpected results," says co-lead author Mi Lei, a graduate student at Caltech.

The optical resonator, which measures just 20 microns in length and includes features smaller than 1 micron, was fabricated at the Kavli Nanoscience Institute at Caltech.

"Through conventional quantum optics measurement techniques, we found that our system had reached an unexplored regime, revealing new physics," says graduate student Rikuto Fukumori, co-lead author of the paper.

Besides the transparency phenomenon, the researchers also observed that the collection of atoms can absorb and emit light from the laser either much faster or much slower compared to a single atom depending on the intensity of the laser. These processes, called superradiance and subradiance, and their underlying physics are still poorly understood because of the large number of interacting quantum particles.

"We were able to monitor and control quantum mechanical lightmatter interactions at nanoscale," says co-corresponding author Joonhee Choi, a former postdoctoral scholar at Caltech who is now an assistant professor at Stanford University.

Though the research is primarily fundamental and expands our understanding of the mysterious world of quantum effects, this discovery has the potential to one day help pave the way to more efficient quantum memories in which information is stored in an ensemble of strongly coupled atoms. Faraon has also worked on creating quantum storage by manipulating the interactions of multiple vanadium atoms.

"Besides memories, these experimental systems provide important insight about developing future connections between quantum computers," says Manuel Endres, professor of physics and Rosenberg Scholar, who is a co-author of the study.

More information: Mi Lei et al, Many-body cavity quantum electrodynamics with driven inhomogeneous emitters, Nature (2023). DOI: 10.1038/s41586-023-05884-1

Journal information: Nature

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Newly observed effect makes atoms transparent to certain frequencies of light - Phys.org

Explainer: Indias quantum computing ambitions – The Financial Express

The Centre has approved Rs 6,003 crore for the National Quantum Mission, to fund scientific and industrial research development in quantum technology. What is quantum technology and why is India so keen on investing in it? Where will the applications of this lie? Sarthak Ray takes a look at these questions

Quantum technology is largely understood as the segment of technology that is based on principles of quantum physics. Quantum physics, in turn, is the study of matter and energy at the most fundamental level, where classical laws of physics dont apply. It aims to uncover the properties and behaviours of the very building blocks of nature, says Caltech.

Also Read: Watch out for AI, multi-cloud & quantum computing in 2023

Quantum physics principles and discoveries already mark their presence in our worldthe discoveries over the decades fuelled innovation and allowed us to come up with devices and applications, such as lasers and transistors, etc. They have also put us forth on the path to quantum computing, which is still under development.

Quantum computers have the same foundational elements as classical onesthey use chips, circuits and logic gates, and operations are orchestrated by algorithms. Data is also transmitted in the binary code of 0s and 1s. Where they differ is classical computing uses bit as the fundamental unit of data; a bit can either be 1 or 0 exclusively.

Quantum computing, on the other hand, uses quantum bits or qubits. A qubit exhibits superpositiona quantum physics principle per which an object exists as the combination of multiple possible states in a simultaneous manner. Imagine waves originating from separate points on a pond and travelling outward. Eventually, waves from the distinct points of origin form a more complex pattern when they overlap. This is superposition. A qubit is a superposition of both 1 and 0 simultaneously until its state is measured.

Why do we need quantum computing? Well, for a start, it offers unprecedented speed of computing. We only have nascent quantum computers now, but the speed achieved by even these is mindblowing. Googles 54-qubit Sycamore processor performed a target computation in 200 seconds; the worlds fastest supercomputer would have taken 10,000 years.

Also Read: Indias first quantum computing-based telecom network link now operational, says Ashwini Vaishnaw

One can make qubits by manipulating normal atoms, atoms carrying electrical charge (or ions), even electrons. They can also be made by nano-engineering artificial atoms, or semiconductor nanocrystals that have their own discrete electronic structure, like atoms. These are made with a printing method callled lithography. The states of different qubits, exhibiting superposition, can get entangledthey can be linked to each other via quantum mechanics.

The computing edge and the impact on a host of areas, including communication, is one that no country would want to miss. There are massive gains to be made in the areas of quantum cryptography and quantum sensing.

So, naturally, many nations, especially the developed ones, have been quick to announce public-sector focus on quantum computing. Six nationsthe US, Canada, China, Finland, France and Germany have loosened their pursestrings to that endthe US has committed $7 billion and China $15 billion.

India, on the other hand, has scaled back fundingwhen the Mission was first announced in 2019, the amount earmarked was Rs 8,000 crore. The latest announcement has scaled back the amount. There are a few Indian companies that are working with MNCs on quantum computing, but what India needs is a push from the government to walk faster on quantum computing research.

Globally, some marquee tech companies are working on quantum computing projects, including IBM. The technology, now, is too costly & cumbersome to get commercialised. For instance, qubits are kept in a chambers that chill them to near absolute zero temperature.

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Explainer: Indias quantum computing ambitions - The Financial Express

Massive Black Holes and Glue Particles Physicists Uncover a … – SciTechDaily

Black holes with dimensions of billions of kilometers (left, as imaged by the Event Horizon Telescope) share features with a dense state of subatomic gluons created in collisions of atomic nuclei (right). Credit: Event Horizon Telescope Collaboration (left) and Brookhaven National Laboratory (right).

Physicists have demonstrated that black holes and the dense state of gluons, which are the glue particles responsible for holding nuclear matter together, have similar characteristics.

Physicists have uncovered a remarkable correspondence between dense gluon states, which are responsible for the strong nuclear force within atomic nuclei, and massive black holes in the universe. Dense gluon walls, referred to as color glass condensate (CGC), emerge from collisions between atomic nuclei and are incredibly small, measuring just 10-19 kilometers in sizeless than a billionth of a kilometer. In stark contrast, black holes can span billions of kilometers.

This groundbreaking research reveals that both systems consist of densely arranged, self-interacting force carrier particles. In the case of CGC, these particles are gluons, while in black holes, they are gravitons. Both the organization of gluons within CGC and gravitons within black holes is optimized for the energy and size of each respective system.

The high degree of order in CGC and black holes is driven by each system packing in the maximal amount of quantum information possible about the particles features. This includes their spatial distributions, velocities, and collective forces. Such limits on information content are universal. This means the research suggests that quantum information science could provide novel organizing principles for understanding these widely different systems.

The mathematical correspondence between these systems also means that studying each can improve our understanding of the other. Of particular interest are comparisons of gravitational shockwaves in black hole mergers with gluon shockwaves in nuclear collisions.

Scientists study the strong force in nuclear collisions. For example, at the Relativistic Heavy Ion Collider, a Department of Energy user facility, atomic nuclei accelerated close to the speed of light become dense walls of gluons known as color glass condensate (CGC). When the nuclei collide, CGC evolves to form a nearly perfect liquid of quarks and gluons, the fundamental building blocks that make up all visible matter.

Though the strong force operates at subatomic scales, this recent analysis by scientists at Ludwig Maximilian University of Munich, the Max Planck Institute for Physics, and Brookhaven National Laboratory shows that CGC shares features with black holes, enormous conglomerates of gravitons that exert gravitational force across the universe.

Both sets of self-interacting particles appear to organize themselves in a way that satisfies a universal limit on the amount of entropy, or disorder, that can exist in each system. This mathematical correspondence points to similarities between black hole formation, thermalization, and decay and what happens when walls of gluons collide in nuclear collisions at ultrarelativistic speedsnear the speed of light.

The limit on entropy that drives this correspondence is related to maximal information packinga key feature of quantum information science (QIS). QIS may therefore further inform scientists understanding of gluons, gravitons, CGC, and black holes. This approach may also advance the design of quantum computers that use cold atoms to simulate and address questions about these complex systems.

Reference: Classicalization and unitarization of wee partons in QCD and gravity: The CGC-black hole correspondence by Gia Dvali and Raju Venugopalan, 29 March 2023, Physical Review D.DOI: 10.1103/PhysRevD.105.056026

The study was fudned by the Department of Energy Office of Science, Nuclear Physics program, the Humboldt Foundation, and the German Research Foundation.

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Massive Black Holes and Glue Particles Physicists Uncover a ... - SciTechDaily

Fighting giants: eco-activist Vandana Shiva on her battle against GM multinationals – The Guardian

Global development

The formidable Indian environmentalist discusses her 50-year struggle to protect seeds and farmers from the poison cartel of corporate agriculture

Fri 28 Apr 2023 01.00 EDT

You dont have to look very far to find the essence of life, says Vandana Shiva. But in a society caught up in a blur of technological advances, bio-hacks and attempts to improve ourselves and the natural world, she fears we are hellbent on destroying it.

Everything comes from the seed, but we have forgotten that the seed isnt a machine, says Shiva. We think we can engineer life, we can change the carefully organised DNA of a living organism, and there will be no wider impact. But this is a dangerous illusion.

For almost five decades, Shiva has been deeply engaged in the fight for environmental justice in India. Regarded as one of the worlds most formidable environmentalists, she has worked to save forests, shut down polluting mines, exposed the dangers of pesticides, spurred on the global campaign for organic farming, championed ecofeminism and gone up against powerful giant chemical corporations.

Her battle to protect the worlds seeds in their natural form rather than genetically altered and commercially controlled versions continues to be her lifes work.

Shivas anti-globalisation philosophy and pilgrimages across India have often been compared to Mahatma Gandhi. Yet while Gandhi became synonymous with the spinning wheel as a symbol of self-reliance, Shivas emblem is the seed.

Now 70, Shiva who is divorced and has one son has spent her life refusing to conform to the patriarchal norms so often imposed on women in India, particularly in the 1950s. She has published more than 20 books and when she is not travelling the world for workshops or speaking tours, she spends her time between her office in Delhi and her organic farm in the foothills of the Himalayas.

She credits her spirit of resistance to her parents, who were feminists at a higher level than Ive ever known long before we even knew the word feminism. After 1947, when India gained independence, her father left the military for a job in the forests of the mountainous state of Uttarakhand, where Shiva was born and brought up always to believe she was equal to men. The forests were my identity and from an early age the laws of nature captivated me, she says.

She was about six when she stumbled on a book of quotes by Albert Einstein buried in a small, musty library in a forest lodge. She was transfixed, determined against all odds to be a physicist. Though science was not taught at her rural convent school, Shivas parents encouraged her curiosity and found ways for her to learn. By the time she was in her 20s, she was completing her PhD in quantum physics at a Canadian university.

Yet as logging, dams and development wreaked ecological devastation on Uttarakhands forests and local peasant women rose up to fight it a movement known as Chipko Shiva realised, on returning to India, that her heart lay not with quantum physics but with a different, nagging question. I couldnt understand why were we told that new technology brings progress, but everywhere I looked, local people were getting poorer and landscapes were being devastated as soon as this development or new technology came in, she says.

In 1982, in her mothers cow shed in the mountain town of Dehradun, Shiva set up her research foundation, exploring the crossover between science, technology and ecology. She began to document the green revolution that swept rural India from the late 1960s, where in a bid to drive up crop yields and avert famine, the government had pushed farmers to introduce technology, mechanisation and agrochemicals.

It instilled in her a lifelong opposition to industrial interference in agriculture. Though the green revolution is acknowledged to have prevented widespread starvation and introduced some necessary modernisation into rural communities, it was also the beginning of a continuing system of monoculture in India, where farmers were pushed to abandon native varieties and instead plant a few high-yielding wheat and rice crops in quick-turnaround cycles, burning the stubble in their fields in between.

It also created a reliance on subsidised fertilisers and chemicals that, though costly and environmentally disastrous, lasts to this day. Soil in fertile states such as Punjab, once known as the breadbasket of India, has been stripped of its rich minerals, with watercourses running dry, rivers polluted with chemical run-off and farmers in a perpetual state of deep crisis and anger.

Shivas suspicions about the chemical industry worsened further when, in the early 1990s, she was privy to some of the first multilateral discussions around agricultural biotechnology and plans by chemical companies to alter crop genes for commercial purposes.

There was a race on by companies to develop and patent these GM crops, but no one was stopping to ask: what will be the impact on the environment? How will they impact on diversity? What will this cost the farmers? They only wanted to win the race and control all the worlds seeds. To me, it all seemed so wrong, says Shiva.

In 1991, five years before the first genetically modified (GM) crops had been planted, she founded Navdanya, meaning nine seeds, an initiative to save Indias native seeds and spread their use among farmers. Eight years later, she took the chemical monolith Monsanto, the worlds largest producer of seeds, to the supreme court for bringing its GM cotton into India without permission.

Monsanto became notorious in the 1960s for producing the herbicide Agent Orange for the US military during the Vietnam war, and subsequently led the development of GM crops in the 1990s. It moved quickly to penetrate the international market with its privatised seeds, particularly in developing, predominantly agricultural countries.

The company, which was bought in 2018 by the German pharmaceutical and biotech company Bayer, became embroiled in legal action. In 2020 it announced a $11bn (8.7bn) payout to settle claims of links between its herbicide and cancer on behalf of almost 100,000 people but denied any wrongdoing. In 2016, dozens of civil society groups staged a peoples tribunal in The Hague, finding Monsanto guilty of human rights violations and developing an unsustainable system of farming.

Shiva says taking Monsanto to court felt like going up against a mafia and alleges that many attempts were made to threaten and pressure her into not filing the case.

Monsanto finally got permission to bring GM cotton to India in 2002, but Shiva has kept up her fight against chemical multinationals, which Shiva refers to as the poison cartel. Currently more than 60% of the worlds commercial seeds are sold by just four companies, which have led the push to patent seeds, orchestrated a global monopoly of certain GM crops such as cotton and soya and sued hundreds of small-scale farmers for saving seeds from commercial crops.

We have taken on these giants when they said weve invented rice, weve invented wheat, and we have won, she says.

She remains adamant that GM crops have failed. But though the legacy of GM pest-resistant cotton in India is complex and has increased pesticide use, not all would agree that the issue is black and white. Indeed, her outspoken and often intransigent positions on GM organisms and globalisation have earned her many critics and powerful enemies.

She has been accused of exaggerating the dangers of GM and simplifying facts around the direct correlation between farmers suicides and genetically modified crops, and been called an enemy of progress for her rhetoric against globalisation, given the threats facing the world.

As the global population has ballooned to 8 billion people, and the climate crisis throws agriculture into disarray, even some prominent environmentalists have shifted their positions and have argued that GM crops can underpin food security. Countries including the UK, which had imposed strict laws around GM foods, are now pushing for more gene editing of crops and animals. Last year India approved the release of a new GM mustard seed.

Shiva is scathing of this renewed push for GM organisms, arguing that much of the gene-editing process is still dangerously unpredictable and calling it ignorance to think climate-adapted crops can only come from industrial labs.

Farmers have already bred thousands of climate-resilient and salt-tolerant seeds; they werent the invention of a few big companies, no matter what patents they claim, she says.

For Shiva, the global crisis facing agriculture will not be solved by the poison cartel nor a continuation of fossil fuel-guzzling, industrialised farming, but instead a return to local, small-scale farming no longer reliant on agrochemicals. Globally, the subsidies are $400bn a year to make an unviable agriculture system work, she says.

This industrialised globalised system of food is destroying soil, it is destroying water and it is generating 30% of our greenhouse gases. If we want to fix this, weve got to shift from industrial to ecological farming.

Nonetheless, while her crusade against the might of chemical corporations will continue, Shiva considers her most important work to be her travels through Indias villages, collecting and saving seeds including 4,000 varieties of rice setting up more than 100 seed banks, and helping farmers return to organic methods.

My proudest work is listening to the seed and her creativity, she says. Im proud of the fact that a lie is a lie is a lie, no matter how big the power that tells the lie. And Im proud that Ive never ever hesitated in speaking the truth.

This article was amended on 28 April 2023. A previous version incorrectly stated that Vandana Shiva had no children; she has a son.

Vandana Shivas latest book, Terra Viva: My Life in a Biodiversity of Movements, is published by Chelsea Green. Shiva will speak at the Extinction or Regeneration conference at the QEII Centre, London, on 11-12 May

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Fighting giants: eco-activist Vandana Shiva on her battle against GM multinationals - The Guardian

Putting hydrogen on solid ground: Simulations with a machine … – EurekAlert

image:Phases of solid hydrogen. The left is the well-studied hexagonal close packed phase, while the right is the new phase predicted by the authors' machine learning-informed simulations. Image by Wesley Moore. view more

Credit: The Grainger College of Engineering at the University of Illinois Urbana-Champaign

Hydrogen, the most abundant element in the universe, is found everywhere from the dust filling most of outer space to the cores of stars to many substances here on Earth. This would be reason enough to study hydrogen, but its individual atoms are also the simplest of any element with just one proton and one electron. For David Ceperley, a professor of physics at the University of Illinois Urbana-Champaign, this makes hydrogen the natural starting point for formulating and testing theories of matter.

Ceperley, also a member of the Illinois Quantum Information Science and Technology Center, uses computer simulations to study how hydrogen atoms interact and combine to form different phases of matter like solids, liquids, and gases. However, a true understanding of these phenomena requires quantum mechanics, and quantum mechanical simulations are costly. To simplify the task, Ceperley and his collaborators developed a machine learning technique that allows quantum mechanical simulations to be performed with an unprecedented number of atoms.They reported in Physical Review Lettersthat their method found a new kind of high-pressure solid hydrogen that past theory and experiments missed.

Machine learning turned out to teach us a great deal, Ceperley said. We had been seeing signs of new behavior in our previous simulations, but we didnt trust them because we could only accommodate small numbers of atoms. With our machine learning model, we could take full advantage of the most accurate methods and see whats really going on.

Hydrogen atoms form a quantum mechanical system, but capturing their full quantum behavior is very difficult even on computers. A state-of-the-art technique like quantum Monte Carlo (QMC) can feasibly simulate hundreds of atoms, while understanding large-scale phase behaviors requires simulating thousands of atoms over long periods of time.

To make QMC more versatile, two former graduate students, Hongwei Niu and Yubo Yang, developed a machine learning model trained with QMC simulations capable of accommodating many more atoms than QMC by itself. They then used the model with postdoctoral research associate Scott Jensen to study how the solid phase of hydrogen that forms at very high pressures melts.

The three of them were surveying different temperatures and pressures to form a complete picture when they noticed something unusual in the solid phase. While the molecules in solid hydrogen are normally close-to-spherical and form a configuration called hexagonal close packedCeperley compared it to stacked orangesthe researchers observed a phase where the molecules become oblong figuresCeperley described them as egg-like.

We started with the not-too-ambitious goal of refining the theory of something we know about, Jensen recalled. Unfortunately, or perhaps fortunately, it was more interesting than that. There was this new behavior showing up. In fact, it was the dominant behavior at high temperatures and pressures, something there was no hint of in older theory.

To verify their results, the researchers trained their machine learning model with data from density functional theory, a widely used technique that is less accurate than QMC but can accommodate many more atoms. They found that the simplified machine learning model perfectly reproduced the results of standard theory. The researchers concluded that their large-scale, machine learning-assisted QMC simulations can account for effects and make predictions that standard techniques cannot.

This work has started a conversation between Ceperleys collaborators and some experimentalists. High-pressure measurements of hydrogen are difficult to perform, so experimental results are limited. The new prediction has inspired some groups to revisit the problem and more carefully explore hydrogens behavior under extreme conditions.

Ceperley noted that understanding hydrogen under high temperatures and pressures will enhance our understanding of Jupiter and Saturn, gaseous planets primarily made of hydrogen. Jensen added that hydrogens simplicity makes the substance important to study. We want to understand everything, so we should start with systems that we can attack, he said. Hydrogen is simple, so its worth knowing that we can deal with it.

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This work was done in collaboration with Markus Holzmann of Univ. Grenoble Alpes and Carlo Pierleoni of the University of LAquila. Ceperleys research group is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Computational Materials Sciences program under Award DE-SC0020177.

Physical Review Letters

Stable Solid Molecular Hydrogen above 900 K from a Machine-Learned Potential Trained with Diffusion Quantum Monte Carlo

17-Feb-2023

Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.

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Putting hydrogen on solid ground: Simulations with a machine ... - EurekAlert

Scientists create a longer-lasting exciton that may open new possibilities in quantum information science – Phys.org

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In a new study, scientists have observed long-lived excitons in a topological material, opening intriguing new research directions for optoelectronics and quantum computing.

Excitons are charge-neutral quasiparticles created when light is absorbed by a semiconductor. Consisting of an excited electron coupled to a lower-energy electron vacancy or hole, an exciton is typically short-lived, surviving only until the electron and hole recombine, which limits its usefulness in applications.

"If we want to make progress in quantum computing and create more sustainable electronics, we need longer exciton lifetimes and new ways of transferring information that don't rely on the charge of electrons," said Alessandra Lanzara, who led the study. Lanzara is a senior faculty scientist at the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) and a UC Berkeley physics professor. "Here we're leveraging topological material properties to make an exciton that is long lived and very robust to disorder."

In a topological insulator, electrons can only move on the surface. By creating an exciton in such a material, the researchers hoped to achieve a state in which an electron trapped on the surface was coupled to a hole that remained confined in the bulk. Such a state would be spatially indirectextending from the surface into the bulkand could retain the special spin properties inherent to topological surface states.

The team used a state-of-the-art technique that Lanzara helped pioneer, known as time-, spin-, and angle-resolved photoemission spectroscopy, which uses ultrafast pulses of light to probe the properties of electrons in a material. They worked with bismuth telluride, a well-studied topological insulator that offered the precise properties they needed: an electronic state combining the topological surface characteristics with those of the insulating bulk.

"We knew that bismuth telluride had the right electronic structure to support a spatially indirect exciton, but finding the right experimental conditions took hundreds of hours," said Lanzara. "It was a huge joy for everyone when we saw the excitonic state we were looking for."

The team studied the formation of the excitonic state and characterized its interaction with other charge carriers in the material. These observations already constituted a breakthrough, but the team went a step further by also measuring the state's spin character and demonstrating the persistence of the topological material's strong spin polarization in the excitonic state.

"We studied this new excitonic state and found that it does indeed inherit characteristics of both excitons and topological states," said first-author Ryo Mori, who worked on this project as a postdoctoral scholar and is now a faculty member at the University of Tokyo. "This finding opens up opportunities for future applications that combine properties of both, such as opto-spintronics and possibly new quantum information technology."

"This work is just the beginning, and many mysteries remain in the fundamental properties," Mori continued. "For example, we still cannot conclude the hole's spin in the current measurement. How does spin affect the exciton pairing mechanism? And then, how do we control the properties of this state so we can use it in an application?"

The research is published in the journal Nature.

More information: Ryo Mori et al, Spin-polarized spatially indirect excitons in a topological insulator, Nature (2023). DOI: 10.1038/s41586-022-05567-3

Journal information: Nature

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Scientists create a longer-lasting exciton that may open new possibilities in quantum information science - Phys.org

Could quantum fluctuations in the early universe enhance the creation of massive galaxy clusters? – Phys.org

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by Ingrid Fadelli , Phys.org

Astrophysicists have been trying to understand the formation of cosmological objects and phenomena in the universe for decades. Past theoretical studies suggest that quantum fluctuations in the early universe, known as primordial quantum diffusion, could have given rise to so-called primordial black holes.

In a paper published in Physical Review Letters, researchers at Niels Bohr Institute, Universidad Autnoma de Madrid and CNRS Universit de Paris recently explored the possibility that these fluctuations could also affect the creation of even larger cosmological structures, such as heavy galaxy clusters like "El Gordo." El Gordo is the largest distant galaxy cluster ever observed using existing telescopes, which was first captured more than 10 years ago.

"The question of how structure formed in the universe might be one of the most ancient ones, but since the early 1980s it has gained a new dimension," Jose Mara Ezquiaga, one of the researchers who carried out the study, told Phys.org. "At the time, scientists realized the incredible connection between the smallest and the largest scales, in which quantum fluctuations in the very early universe are stretched by a cosmic inflation to seed the formation of galaxies and large-scale structures in the universe."

After physicists first started learning more about the connections between the early and late universe, the idea that black holes could be formed in the early universe started emerging. In 2015, the first observations of black hole mergers via gravitational waves renewed interest in this area, sparking new theoretical studies focusing on the primordial origin of black holes.

"Juan, Vincent and I had been investigating the formation of primordial black holes in the early universe," Ezquiaga said. "Our key contribution was realizing that when quantum fluctuations are dominating the dynamics of cosmic inflation, this leads to a spectrum of density fluctuations that is non-Gaussian, with heavy exponential tails. In other words, quantum diffusion makes it easier to generate large fluctuations that would collapse into a primordial black hole."

After studying primordial black holes in the early universe, Ezquiaga and his colleagues Vincent Vennin and Juan Garcia-Bellido started wondering whether the same mechanism underpinning their formation, namely an enhanced non-Gaussian tail in the distribution of primordial perturbations, could also lead to the formation of other very large cosmological structures. In their recent work, they specifically explored the possibility that this mechanism affects the collapse of larger objects such as dark matter halos, which will later host galaxies and groups of galaxies.

"The formation of larger objects early on in the history of the universe could help alleviate some tensions between observations and our standard cosmological model," Ezquiaga explained. "For example, under standard assumptions, massive clusters like El Gordo may look like outlier, while quantum diffusion make them natural."

As part of their recent study, Ezquiaga and his colleagues computed the halo mass function and cluster abundance as a function of redshift in the presence of heavy exponential tails. This allowed them to determine whether quantum diffusion could increase the number of large galaxy clusters, depleting dark matter halos.

"Because gravity is always attractive, inhomogeneities will only grow as overdensities will attract mass for their surroundings and under densities will become emptier," Ezquiaga said. "The question is whether inhomogeneities in the early universe are large and frequent enough to lead to the gravitational collapse necessary to explain the observed structures in the cosmos. Given an initial distribution of perturbations one only needs to press 'play' and let the system evolve gravitationally, In our case, we had a previous understanding of the distribution of initial perturbations when including quantum diffusion, so our job in this work was to parametrize in a suitable way this spectrum and analyze the results for the number of massive clusters as a function of redshift."

The researchers' paper suggests that quantum fluctuations in the early universe might not only underly the formation of average-sized galaxies and primordial black holes, but also that of massive galaxy clusters, like the fascinating "El Gordo" and Pandora clusters. This would mean that current observations of galaxy clusters could be explained using existing theories, without the need to incorporate new physics in the standard model.

"The other very exciting outcome of our work is that it predicts unique signatures that could be tested in the near future," Ezquiaga said. "In particular, we demonstrate that quantum diffusion not only makes heavy clusters easier to form early on, but also that the amount of substructure should be lower than expected."

The simultaneous enhancement of massive cosmological structures and the depletion of substructures (i.e., halos) is not predicted by other theoretical models. Nonetheless, this potential theoretical explanation for the formation of large galaxy clusters appears to be aligned with recent cosmological observations and could also potentially solve other shortcomings of the standard model.

In their next studies, Ezquiaga and his colleagues would like to paint a more complete picture of the structures in the universe and their formation. This could ultimately also help to fully probe the predictions of quantum diffusion.

"Next for us is fully testing the predictions of this model against observations," Ezquiaga added. "Luckily, there are many new observations that we can use. In particular, the very recent observations of James Webb Space Telescope seem to indicate that there are many more massive galaxies at high redshift, somethings naturally aligning with our predictions, but we are waiting for astronomers to fully understand their systematics and confirm this 'unexpected' population. The other observations that might be interesting for us are number counts of dwarf galaxies with galaxy surveys like the Dark Energy Survey and constraints on subhalos from strong lensing."

More information: Jose Mara Ezquiaga et al, Massive Galaxy Clusters Like El Gordo Hint at Primordial Quantum Diffusion, Physical Review Letters (2023). DOI: 10.1103/PhysRevLett.130.121003

Journal information: Physical Review Letters

2023 Science X Network

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Next Generation miniMOT Platform Unveiled for Quantum Physics Research and Education – Yahoo Finance

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Infleqtion has collaborated with undergraduate educators to develop experiments that can be integrated into traditional physics curricula. As atomic physicists, they understand the importance of incorporating physical experimentation based on quantum physics into physics education. This is crucial as quantum technologies, such as quantum information processing, Positioning, Navigation and Time-keeping (PNT), gravimetry, and magnetometry, have become increasingly important for industry and governments around the world. To take advantage of the opportunities that the quantum world will offer, it is critical to develop a workforce with the necessary skill sets.

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Next Generation miniMOT Platform Unveiled for Quantum Physics Research and Education - Yahoo Finance