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  • richardmitnick 8:05 am on July 4, 2022 Permalink | Reply
    Tags: "Keeping the Energy in The Room", "MKIDs": Microwave Kinetic Inductance Detectors, A Cooper pair is able to move about without resistance., A thin layer of the metal indium-placed between the superconducting sensor and the substrate-drastically reduced the energy leaking out of the sensor., An MKID Exoplanet Camera can detect even faint signals., An MKID uses a superconductor in which electricity can flow with no resistance., , , CMOS sensors are semiconductors based on silicon., , In a superconductor all the electrons are paired up., In a superconductor two electrons will pair up-one spin up and one spin down-in a Cooper pair., , Right now scientists can only do spectroscopy for a tiny subset of exoplanets-those where the planet passes between its star and Earth., Scientists can use spectroscopy to identify the composition of objects both nearby and across the entire visible universe., Sensor Technology, superconductors, The gap energy in a superconductor is about 10000 times less than in semiconductors based on silicon., The indium essentially acted like a fence., The photo-electric effect CMOS sensor: a photon strikes the sensor knocking off an electron that can then be detected as a signal suitable for processing by a microprocessor., The scientists chose indium because it is also a superconductor at the temperatures at which the MKID will operate and adjacent superconductors tend to cooperate if they are thin., The technique cut down the wavelength measurement uncertainty from 10% to 5%., , This will all soon be possible with the capabilities of the next generation of 30-meter telescopes., With better MKIDs scientists can use light reflected off the surface of a planet rather than transmitted through its narrow atmosphere alone.   

    From The University of California-Santa Barbara: “Keeping the Energy in The Room” 

    UC Santa Barbara Name bloc

    From The University of California-Santa Barbara

    July 1, 2022

    Harrison Tasoff
    (805) 893-7220
    harrisontasoff@ucsb.edu

    Professor Ben Mazin talks superconductors, exoplanets and dance clubs as he explains advances in sensor technology.

    1
    The sensor mounted for use in an MKID Exoplanet Camera. Photo Credit: Ben Mazin.

    It may seem like technology advances year after year, as if by magic. But behind every incremental improvement and breakthrough revolution is a team of scientists and engineers hard at work.

    UC Santa Barbara Professor Ben Mazin is developing precision optical sensors for telescopes and observatories. In a paper published in Physical Review Letters, he and his team improved the spectra resolution of their superconducting sensor, a major step in their ultimate goal: analyzing the composition of exoplanets.

    “We were able to roughly double the spectral resolving power of our detectors,” said first author Nicholas Zobrist, a doctoral student in the Mazin Lab.

    “This is the largest energy resolution increase we’ve ever seen,” added Mazin. “It opens up a whole new pathway to science goals that we couldn’t achieve before.”

    The Mazin lab works with a type of sensor called an MKID. Most light detectors — like the CMOS sensor in a phone camera — are semiconductors based on silicon. These operate via the photo-electric effect: a photon strikes the sensor knocking off an electron that can then be detected as a signal suitable for processing by a microprocessor.

    An MKID uses a superconductor in which electricity can flow with no resistance. In addition to zero resistance, these materials have other useful properties. For instance, semiconductors have a gap energy that needs to be overcome to knock the electron out. The related gap energy in a superconductor is about 10,000 times less, so it can detect even faint signals.

    What’s more, a single photon can knock many electrons off of a superconductor, as opposed to only one in a semiconductor. By measuring the number of mobile electrons, an MKID can actually determine the energy (or wavelength) of the incoming light. “And the energy of the photon, or its spectra, tells us a lot about the physics of what emitted that photon,” Mazin said.

    Leaking energy

    The researchers had hit a limit as to how sensitive they could make these MKIDs. After much scrutiny, they discovered that energy was leaking from the superconductor into the sapphire crystal wafer that the device is made on. As a result, the signal appeared weaker than it truly was.

    In typical electronics, current is carried by mobile electrons. But these have a tendency to interact with their surroundings, scattering and losing energy in what’s known as resistance. In a superconductor two electrons will pair up — one spin up and one spin down — and this Cooper pair, as it’s called, is able to move about without resistance.

    “It’s like a couple at a club,” Mazin explained. “You’ve got two people who pair up, and then they can move together through the crowd without any resistance. Whereas a single person stops to talk to everybody along the way, slowing them down.”

    In a superconductor, all the electrons are paired up. “They’re all dancing together, moving around without interacting with other couples very much because they’re all gazing deeply into each other’s eyes.

    “A photon hitting the sensor is like someone coming in and spilling a drink on one of the partners,” he continued. “This breaks the couple up, causing one partner to stumble into other couples and create a disturbance.” This is the cascade of mobile electrons that the MKID measures.

    But sometimes this happens at the edge of the dancefloor. The offended party stumbles out of the club without knocking into anyone else. Great for the rest of the dancers, but not for the scientists. If this happens in the MKID, then the light signal will seem weaker than it actually was.

    Fencing them in

    Mazin, Zobrist and their co-authors discovered that a thin layer of the metal indium — placed between the superconducting sensor and the substrate — drastically reduced the energy leaking out of the sensor. The indium essentially acted like a fence around the dancefloor, keeping the jostled dancers in the room and interacting with the rest of the crowd.

    They chose indium because it is also a superconductor at the temperatures at which the MKID will operate, and adjacent superconductors tend to cooperate if they are thin. The metal did present a challenge to the team, though. Indium is softer than lead, so it has a tendency to clump up. That’s not great for making the thin, uniform layer the researchers needed.

    But their time and effort paid off. The technique cut down the wavelength measurement uncertainty from 10% to 5%, the study reports. For example, photons with a wavelength of 1,000 nanometers can now be measured to a precision of 50 nm with this system. “This has real implications for the science we can do,” Mazin said, “because we can better resolve the spectra of the objects that we’re looking at.”

    Different phenomena emit photons with specific spectra (or wavelengths), and different molecules absorb photons of different wavelengths. Using this light, scientists can use spectroscopy to identify the composition of objects both nearby and across the entire visible universe.

    Mazin is particularly interested in applying these detectors to exoplanet science. Right now scientists can only do spectroscopy for a tiny subset of exoplanets. The planet needs to pass between its star and Earth, and it must have a thick atmosphere so that enough light passes through it for researchers to work with. Still, the signal to noise ratio is abysmal, especially for rocky planets, Mazin said.

    With better MKIDs scientists can use light reflected off the surface of a planet rather than transmitted through its narrow atmosphere alone. This will soon be possible with the capabilities of the next generation of 30-meter telescopes.

    The Mazin group is also experimenting with a completely different approach to the energy-loss issue. Although the results from this paper are impressive, Mazin said he believes the indium technique could be obsolete if his team is successful with this new endeavor. Either way, he added, the scientists are rapidly closing in on their goals.

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    UC Santa Barbara Seal

    The University of California-Santa Barbara is a public land-grant research university in Santa Barbara, California, and one of the ten campuses of the University of California system. Tracing its roots back to 1891 as an independent teachers’ college, The University of California-Santa Barbara joined the University of California system in 1944, and is the third-oldest undergraduate campus in the system.

    The university is a comprehensive doctoral university and is organized into five colleges and schools offering 87 undergraduate degrees and 55 graduate degrees. It is classified among “R1: Doctoral Universities – Very high research activity”. According to the National Science Foundation, The University of California-Santa Barbara spent $235 million on research and development in fiscal year 2018, ranking it 100th in the nation. In his 2001 book The Public Ivies: America’s Flagship Public Universities, author Howard Greene labeled The University of California-Santa Barbara a “Public Ivy”.

    The University of California-Santa Barbara is a research university with 10 national research centers, including the Kavli Institute for Theoretical Physics and the Center for Control, Dynamical-Systems and Computation. Current University of California-Santa Barbara faculty includes six Nobel Prize laureates; one Fields Medalist; 39 members of the National Academy of Sciences; 27 members of the National Academy of Engineering; and 34 members of the American Academy of Arts and Sciences. The University of California-Santa Barbara was the No. 3 host on the ARPANET and was elected to the Association of American Universities in 1995. The faculty also includes two Academy and Emmy Award winners and recipients of a Millennium Technology Prize; an IEEE Medal of Honor; a National Medal of Technology and Innovation; and a Breakthrough Prize in Fundamental Physics.
    The University of California-Santa Barbara Gauchos compete in the Big West Conference of the NCAA Division I. The Gauchos have won NCAA national championships in men’s soccer and men’s water polo.

    History

    The University of California-Santa Barbara traces its origins back to the Anna Blake School, which was founded in 1891, and offered training in home economics and industrial arts. The Anna Blake School was taken over by the state in 1909 and became the Santa Barbara State Normal School which then became the Santa Barbara State College in 1921.

    In 1944, intense lobbying by an interest group in the City of Santa Barbara led by Thomas Storke and Pearl Chase persuaded the State Legislature, Gov. Earl Warren, and the Regents of the University of California to move the State College over to the more research-oriented University of California system. The State College system sued to stop the takeover but the governor did not support the suit. A state constitutional amendment was passed in 1946 to stop subsequent conversions of State Colleges to University of California campuses.

    From 1944 to 1958, the school was known as Santa Barbara College of the University of California, before taking on its current name. When the vacated Marine Corps training station in Goleta was purchased for the rapidly growing college Santa Barbara City College moved into the vacated State College buildings.

    Originally the regents envisioned a small several thousand–student liberal arts college a so-called “Williams College of the West”, at Santa Barbara. Chronologically, The University of California-Santa Barbara is the third general-education campus of the University of California, after The University of California-Berkeley and The University of California-Los Angeles (the only other state campus to have been acquired by the University of California system). The original campus the regents acquired in Santa Barbara was located on only 100 acres (40 ha) of largely unusable land on a seaside mesa. The availability of a 400-acre (160 ha) portion of the land used as Marine Corps Air Station Santa Barbara until 1946 on another seaside mesa in Goleta, which the regents could acquire for free from the federal government, led to that site becoming the Santa Barbara campus in 1949.

    Originally only 3000–3500 students were anticipated but the post-WWII baby boom led to the designation of general campus in 1958 along with a name change from “Santa Barbara College” to “University of California-Santa Barbara,” and the discontinuation of the industrial arts program for which the state college was famous. A chancellor- Samuel B. Gould- was appointed in 1959.

    In 1959 The University of California-Santa Barbara professor Douwe Stuurman hosted the English writer Aldous Huxley as the university’s first visiting professor. Huxley delivered a lectures series called The Human Situation.

    In the late ’60s and early ’70s The University of California-Santa Barbara became nationally known as a hotbed of anti–Vietnam War activity. A bombing at the school’s faculty club in 1969 killed the caretaker Dover Sharp. In the spring of 1970 multiple occasions of arson occurred including a burning of the Bank of America branch building in the student community of Isla Vista during which time one male student Kevin Moran was shot and killed by police. The University of California-Santa Barbara ‘s anti-Vietnam activity impelled then-Gov. Ronald Reagan to impose a curfew and order the National Guard to enforce it. Armed guardsmen were a common sight on campus and in Isla Vista during this time.

    In 1995 The University of California-Santa Barbara was elected to the Association of American Universities– an organization of leading research universities with a membership consisting of 59 universities in the United States (both public and private) and two universities in Canada.

    On May 23, 2014 a killing spree occurred in Isla Vista, California, a community in close proximity to the campus. All six people killed during the rampage were students at The University of California-Santa Barbara. The murderer was a former Santa Barbara City College student who lived in Isla Vista.

    Research activity

    According to the National Science Foundation, The University of California-Santa Barbara spent $236.5 million on research and development in fiscal 2013, ranking it 87th in the nation.

    From 2005 to 2009 UCSB was ranked fourth in terms of relative citation impact in the U.S. (behind Massachusetts Institute of Technology, California Institute of Technology, and Princeton University) according to Thomson Reuters.

    The University of California-Santa Barbara hosts 12 National Research Centers, including The Kavli Institute for Theoretical Physics, the National Center for Ecological Analysis and Synthesis, the Southern California Earthquake Center, the UCSB Center for Spatial Studies, an affiliate of the National Center for Geographic Information and Analysis, and the California Nanosystems Institute. Eight of these centers are supported by The National Science Foundation. UCSB is also home to Microsoft Station Q, a research group working on topological quantum computing where American mathematician and Fields Medalist Michael Freedman is the director.

    Research impact rankings

    The Times Higher Education World University Rankings ranked The University of California-Santa Barbara 48th worldwide for 2016–17, while the Academic Ranking of World Universities (ARWU) in 2016 ranked https://www.nsf.gov/ 42nd in the world; 28th in the nation; and in 2015 tied for 17th worldwide in engineering.

    In the United States National Research Council rankings of graduate programs, 10 University of California-Santa Barbara departments were ranked in the top ten in the country: Materials; Chemical Engineering; Computer Science; Electrical and Computer Engineering; Mechanical Engineering; Physics; Marine Science Institute; Geography; History; and Theater and Dance. Among U.S. university Materials Science and Engineering programs, The University of California-Santa Barbara was ranked first in each measure of a study by the National Research Council of the NAS.

    The Centre for Science and Technologies Studies at

     
  • richardmitnick 6:30 am on June 11, 2022 Permalink | Reply
    Tags: "LiFeAs", "MZM": Majorana-zero-mode lattice, "Scientists Observe Large-scale and Ordered and Tunable Majorana-zero-mode Lattice", A new pathway towards future topological quantum computation, , , , , superconductors,   

    From The Chinese Academy of Sciences [中国科学院](CN): “Scientists Observe Large-scale and Ordered and Tunable Majorana-zero-mode Lattice” 

    From The Chinese Academy of Sciences [中国科学院](CN)

    Jun 10, 2022
    GAO Hongjun
    Institute of Physics
    hjgao@iphy.ac.cn

    1
    Fig. 1. Characterization of biaxial CDW region. (Image by Institute of Physics)

    2
    Fig. 2. MZM in vortices. (Image by Institute of Physics)

    3
    Fig. 3. Majorana mechanism in “LiFeAs”. (Image by Institute of Physics)

    4
    Fig. 4. Tuning the MZM lattice with magnetic field. (Image by Institute of Physics)

    In a study published in Nature on June 8, a joint research team led by Prof. GAO Hongjun from the Institute of Physics of the Chinese Academy of Sciences (CAS) has reported observation of a large-scale, ordered and tunable Majorana-zero-mode (MZM) lattice in the iron-based superconductor “LiFeAs”, providing a new pathway towards future topological quantum computation.

    MZMs are zero-energy bound states confined in the topological defects of crystals, such as line defects and magnetic field-induced vortices. They are characterized by scanning tunnelling microscopy/spectroscopy (STM/S) as zero-bias conductance peaks. They obey non-Abelian statistics and are considered building blocks for future topological quantum computation.

    MZMs have been observed in several topologically nontrivial iron-based superconductors, such as Fe (Te0.55Se0.45), (Li0.84Fe0.16)OHFeSe, and CaKFe4As4. However, these materials suffer from issues with alloying-induced disorder, uncontrollable and disordered vortex lattices, and the low yield of topological vortices, all of which hinder their further study and application.

    In this study, the researchers observed the formation of an ordered and tunable MZM lattice in the naturally strained superconductor “LiFeAs”. Using STM/S equipped with magnetic fields, the researchers found that local strain naturally exists in “LiFeAs”. Biaxial charge density wave (CDW) stripes along the Fe-Fe and As-As directions are produced by the strain, with wave vectors of λ1~2.7 nm and λ2~24.3 nm. The CDW with wavevector λ2 shows strong modulation on the superconductivity of “LiFeAs”.

    Under a magnetic field perpendicular to the sample surface, the vortices emerge and are forced to align exclusively along the As-As CDW stripes, forming an ordered lattice. The reduced crystal symmetry leads to a drastic change in the topological band structures at the Fermi level, thus transforming the vortices into topological ones hosting MZMs and forming an ordered MZM lattice. Moreover, the MZM lattice density and geometry are tunable by an external magnetic field. The MZMs start to couple with each other under high magnetic fields.

    This observation of a large-scale, ordered and tunable MZM lattice in “LiFeAs” expands the MZM family found in iron-based superconductors, thus providing a promising platform for manipulating and braiding MZMs in the future, according to the researchers.

    These findings may shed light on the study of topological quantum computation using iron-based superconductors.

    This study was supported by the National Science Foundation of China, the Ministry of Science and Technology of China, and CAS.

    See the full article here.

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    The Chinese Academy of Sciences[中国科学院](CN) is the national academy for the natural sciences of the People’s Republic of China. It has historical origins in the Academia Sinica during the Republican era and was formerly also known by that name. Collectively known as the “Two Academies (两院)” along with the Chinese Academy of Engineering, it functions as the national scientific think tank and academic governing body, providing advisory and appraisal services on issues stemming from the national economy, social development, and science and technology progress. It is headquartered in Xicheng District, Beijing, with branch institutes all over mainland China. It has also created hundreds of commercial enterprises, Lenovo being one of the most famous.

    It is the world’s largest research organization, comprising around 60,000 researchers working in 114 institutes, and has been consistently ranked among the top research organizations around the world. It also holds the University of Science and Technology of China and the University of Chinese Academy of Sciences.

    The Chinese Academy of Sciences has been ranked the No. 1 research institute in the world by Nature Index since the list’s inception in 2016 by Nature Portfolio. It is the most productive institution publishing articles of sustainable development indexed in Web of Science from 1981 to 2018 among all universities and research institutions in the world.

    The Chinese Academy originated in the Academia Sinica founded, in 1928, by the Republic of China. After the Communist Party took control of mainland China in 1949, the residual of Academia Sinica was renamed Chinese Academy of Sciences (CAS), while others relocated to Taiwan.

    The Chinese Academy of Sciences has six academic divisions:

    Chemistry (化学部)
    Information Technological Sciences (信息技术科学部)
    Earth Sciences (地学部)
    Life Sciences and Medical Sciences (生命科学和医学学部)
    Mathematics and Physics (数学物理学部)
    Technological Sciences (技术科学部)

    The CAS has thirteen regional branches, in Beijing, Shenyang, Changchun, Shanghai, Nanjing, Wuhan, Guangzhou, Chengdu, Kunming, Xi’an, Lanzhou, Hefei and Xinjiang. It has over one hundred institutes and four universities (the University of Science and Technology of China at Hefei, Anhui, the University of the Chinese Academy of Sciences in Beijing, ShanghaiTech University, and Shenzhen Institute of Adavanced Technology). Backed by the institutes of CAS, UCAS is headquartered in Beijing, with graduate education bases in Shanghai, Chengdu, Wuhan, Guangzhou and Lanzhou, four Science Libraries of Chinese Academy of Sciences, three technology support centers and two news and publishing units. These CAS branches and offices are located in 20 provinces and municipalities throughout China. CAS has invested in or created over 430 science- and technology-based enterprises in eleven industries, including eight companies listed on stock exchanges.

    Being granted a Fellowship of the Academy represents the highest level of national honor for Chinese scientists. The CAS membership system includes Academicians (院士), Emeritus Academicians (荣誉院士) and Foreign Academicians (外籍院士).

    The Chinese Academy of Sciences was ranked #1 in the 2016, 2017, 2018, 2019, and 2020 Nature Index Annual Tables, which measure the largest contributors to papers published in 82 leading journals.

    Research institutes

    Beijing Branch
    University of the Chinese Academy of Sciences (UCAS)
    Academy of Mathematics and Systems Science
    Institute of Acoustics (IOA)
    Institute of Atmospheric Physics
    Institute of Botany, Chinese Academy of Sciences
    Institute of Physics (IOPCAS)
    Institute of Semiconductors
    Institute of Electrical Engineering (IEE)
    Institute of Information Engineering (IIE)
    Institute of Theoretical Physics
    Institute of High Energy Physics
    Institute of Biophysics
    Institute of Genetics and Developmental Biology
    Institute of Electronics
    National Astronomical Observatories
    Institute of Computing Technology
    Institute of Software
    Institute of Automation
    Beijing Institute of Genomics
    Institute of Geographic Sciences and Natural Resources
    Institute of Geology and Geophysics (IGG)
    Institute of Remote Sensing and Digital Earth
    Institute of Tibetan Plateau Research
    Institute of Vertebrate Paleontology and Paleoanthropology
    National Center for Nanoscience and Technology
    Institute of Policy and Management
    Institute of Psychology
    Institute of Zoology
    Changchun Branch
    Changchun Institute of Optics, Fine Mechanics and Physics
    Changchun Institute of Applied Chemistry
    Northeast Institute of Geography and Agroecology
    Changchun Observatory
    Chengdu Branch
    Institute of Mountain Hazards and Environment
    Chengdu Institute of Biology
    Institute of Optics and Electronics
    Chengdu Institute of Organic Chemistry
    Institute of Computer Application
    Chongqing Institute of Green and Intelligent Technology
    Guangzhou Branch
    South China Botanical Garden
    Shenzhen Institutes of Advanced Technology
    South China Sea Institute of Oceanology
    Guangzhou Institute of Energy Conversion
    Guangzhou Institute of Geochemistry
    Guangzhou Institute of Biomedicine and Health
    Guiyang Branch
    Institute of Geochemistry
    Hefei Branch
    Hefei Institutes of Physical Science
    University of Science and Technology of China
    Kunming Branch
    Kunming Institute of Botany
    Kunming Institute of Zoology
    Xishuangbanna Tropical Botanical Garden
    Institute of Geochemistry
    Yunnan Astronomical Observatory
    Lanzhou Branch
    Institute of Modern Physics
    Lanzhou Institute of Chemical Physics
    Lanzhou Institute of Geology
    Northwest Institute of Plateau Biology
    Northwest Institute of Eco-Environment and Resources
    Qinghai Institute of Salt Lakes Research
    Nanjing Branch
    Purple Mountain Observatory (Zijinshan Astronomical Observatory)
    Institute of Soil Science
    Nanjing Institute of Geology and Palaeontology
    Nanjing Institute of Geography and Limnology
    Nanjing Institute of Astronomical Optics and Technology
    Suzhou Institute of Nano-tech and Nano-bionics (SINANO)
    Suzhou Institute of Biomedical Engineering and Technology (SIBET)
    Nanjing Botanical Garden, Memorial Sun Yat-Sen (Institute of Botany, Jiangsu Province and Chinese Academy of Science)
    University of Chinese Academy of Sciences, Nanjing College
    Shanghai Branch
    Shanghai Astronomical Observatory
    Shanghai Institute of Microsystem and Information Technology
    Shanghai Institute of Technical Physics
    Shanghai Institute of Optics and Fine Mechanics
    Shanghai Institute of Ceramics
    Shanghai Institute of Organic Chemistry
    Shanghai Institute of Applied Physics
    Shanghai Institutes for Biological Sciences
    Shanghai Institute of Materia Medica
    Institut Pasteur of Shanghai
    Shanghai Advanced Research Institute, CAS
    Institute of Neuroscience (ION)
    ShanghaiTech University
    Shenyang Branch
    Institute of Metal Research
    Shenyang Institute of Automation
    Shenyang Institute of Applied Ecology, formerly the Institute of Forestry and Pedology
    Shenyang Institute of Computing Technology
    Dalian Institute of Chemical Physics
    Qingdao Institute of Oceanology
    Qingdao Institute of Bioenergy and Bioprocess Technology
    Yantai Institute of Coastal Zone Research
    Taiyuan Branch
    Shanxi Institute of Coal Chemistry (ICCCAS)
    Wuhan Branch
    Wuhan Institute of Rock and Soil Mechanics
    Wuhan Institute of Physics and Mathematics
    Wuhan Institute of Virology
    Institute of Geodesy and Geophysics
    Institute of Hydrobiology
    Wuhan Botanical Garden
    Xinjiang Branch
    Xinjiang Technical Institute of Physics and Chemistry
    Xinjiang Institute of Ecology and Geography
    Xi’an Branch
    Xi’an Institute of Optics and Precision Mechanics
    National Time Service Center
    Institute of Earth Environment

     
  • richardmitnick 2:48 pm on February 10, 2020 Permalink | Reply
    Tags: "Quantum technologies: New insights into superconducting processes", , Carsten Schuck's research group at Münster University has been working for several years on developing such single-photon detectors based on superconductors., Forschungszentrum Jülich, High temperature superconducting microbridge, , , superconductors, University of Münster   

    From University of Münster: “Quantum technologies: New insights into superconducting processes” 

    1

    From University of Münster

    10. February 2020

    1
    Measurement setup for the characterization of microbridges in a cryostat

    Physicists demonstrate energy quantization in high-temperature superconductors / Study in “Nature Communications”

    The development of a quantum computer that can solve problems, which classical computers can only solve with great effort or not at all – this is the goal currently being pursued by an ever-growing number of research teams worldwide. The reason: Quantum effects, which originate from the world of the smallest particles and structures, enable many new technological applications. So-called superconductors, which allow for processing information and signals according to the laws of quantum mechanics, are considered to be promising components for realizing quantum computers. A sticking point of superconducting nanostructures, however, is that they only function at very low temperatures and are therefore difficult to bring into practical applications.

    Researchers at the University of Münster and Forschungszentrum Jülich now, for the first time, demonstrated what is known as energy quantization in nanowires made of high-temperature superconductors – i. e. superconductors, in which the temperature is elevated below which quantum mechanical effects predominate. The superconducting nanowire then assumes only selected energy states that could be used to encode information. In the high-temperature superconductors, the researchers were also able to observe for the first time the absorption of a single photon, a light particle that serves to transmit information.

    “On the one hand, our results can contribute to the use of considerably simplified cooling technology in quantum technologies in the future, and on the other hand, they offer us completely new insights into the processes governing superconducting states and their dynamics, which are still not understood,” emphasizes study leader Jun. Prof. Carsten Schuck from the Institute of Physics at Münster University. The results may therefore be relevant for the development of new types of computer technology. The study has been published in the journal Nature Communications.

    Background and methods:

    2
    High temperature superconducting microbridge (pink) in gold contacts (yellow)
    © M. Lyatti et al./ Nature Communications

    The scientists used superconductors made of the elements yttrium, barium, copper oxide and oxygen, or YBCO for short, from which they fabricated a few nanometer thin wires. When these structures conduct electrical current physical dynamics called phase slips occur. In the case of YBCO nanowires fluctuations of the charge carrier density cause variations in the supercurrent. The researchers investigated the processes in the nanowires at temperatures below 20 Kelvin, which corresponds to minus 253 degrees Celsius. In combination with model calculations, they demonstrated a quantization of energy states in the nanowires. The temperature at which the wires entered the quantum state was found at 12 to 13 Kelvin – a temperature several hundred times higher than the temperature required for the materials normally used. This enabled the scientists to produce resonators, i.e. oscillating systems tuned to specific frequencies, with much longer lifetimes and to maintain the quantum mechanical states for longer. This is a prerequisite for the long-term development of ever larger quantum computers.

    Absorption of a single photon in high-temperature superconductors

    Further important components for the development of quantum technologies, but potentially also for medical diagnostics, are detectors that can register even single-photons. Carsten Schuck’s research group at Münster University has been working for several years on developing such single-photon detectors based on superconductors. What already works well at low temperatures, scientists all over the world have been trying to achieve with high-temperature superconductors for more than a decade. In the YBCO nanowires used for the study, this attempt has now succeeded for the first time. “Our new findings pave the way for new experimentally verifiable theoretical descriptions and technological developments,” says co-author Martin Wolff from the Schuck research group.

    Participating institutions and funding:

    The superconducting films produced at Forschungszentrum Jülich were nanostructured in Jülich and at the University of Münster, where also the experimental characterization was carried out. The study received financial support from the Ministry of Economics, Innovation, Digitization and Energy of the State of North Rhine-Westphalia and the Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons (ER-C) of the Forschungszentrum Jülich.

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    Sitz der WWU
    Foto: MünsterView/Tronquet

    The University of Münster (German: Westfälische Wilhelms-Universität Münster, WWU) is a public university located in the city of Münster, North Rhine-Westphalia in Germany.

    With more than 43,000 students and over 120 fields of study in 15 departments, it is Germany’s fifth largest university and one of the foremost centers of German intellectual life. The university offers a wide range of subjects across the sciences, social sciences and the humanities. Several courses are also taught in English, including PhD programmes as well as postgraduate courses in geoinformatics, geospational technologies or information systems.

    Professors and former students have won ten Leibniz Prizes, the most prestigious as well as the best-funded prize in Europe, and one Fields Medal. The WWU has also been successful in the German government’s Excellence Initiative.

     
  • richardmitnick 9:21 am on September 3, 2019 Permalink | Reply
    Tags: , , , Scientists have calculated that a hydrogen-rich compound could conduct electricity without resistance at temperatures up to about 200° Celsius., superconductors, The newly predicted superconductor — a compound of hydrogen; magnesium; and lithium — comes with its own complications however., The proposed superconductor must be squeezed to extremely high pressure nearly 2.5 million times the pressure of Earth’s atmosphere.   

    From Science News: “A predicted superconductor might work at a record-breaking 200° Celsius” 

    From Science News

    August 30, 2019
    Emily Conover

    1
    A theoretical type of superconductor, made of atoms of lithium (illustrated in green), magnesium (blue) and hydrogen (red), could function even at temperatures above the boiling point of water, scientists say. H. Liu

    The hydrogen-rich material would still need to be squeezed to extremely high pressures.

    Scientists have calculated that a hydrogen-rich compound could conduct electricity without resistance [Physical Review Letters] at temperatures up to about 200° Celsius — well above the 100° C boiling point of water. If that prediction is confirmed experimentally, the material would stand in stark contrast to all other known superconductors, which must be cooled below room temperature to work (SN: 12/15/15).

    The newly predicted superconductor — a compound of hydrogen, magnesium and lithium — comes with its own complications, however. It must be squeezed to extremely high pressure, nearly 2.5 million times the pressure of Earth’s atmosphere, physicist Hanyu Liu and colleagues, of Jilin University in Changchun, China, report in the Aug. 30 Physical Review Letters [link above].

    Scientists previously have used similar techniques to predict that a pressurized compound of lanthanum and hydrogen would be superconducting at higher temperatures than any yet known. That prediction seems likely to be correct: In 2018, physicist Russell Hemley and colleagues reported signs that the compound is superconducting up to a record-breaking −13° C (SN: 9/10/18).

    If the new calculation is confirmed, the purported superconductor would smash Hemley and colleagues’ temperature record. “This is an important prediction using a level of theory that has proven quite accurate,” says Hemley, of the University of Illinois at Chicago, who was not involved in the research.

    See the full article here .


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  • richardmitnick 6:09 pm on March 4, 2019 Permalink | Reply
    Tags: “What is interesting” says first author Tatsuya Kaneko a postdoctoral researcher at the RIKEN Cluster for Pioneering Research “is that our calculations showed that this takes place based on the , But for the present study the researchers used non-equilibrium dynamics to analyze the effect of pulses of light on a Mott insulator and found that the effect would in fact happen in the real world, , , Scientists from the RIKEN Cluster for Pioneering Research have shown that pulses of light could be used to turn these materials beyond simple conductors to superconductors—materials that conduct ele, superconductors, Thirty years ago the mathematical physicist Chen-Ning Yang originally proposed the idea of eta-pairing but because it was a purely mathematical concept it was understood as a virtual phenomenon that w, This process would happen through an unconventional type of superconductivity known as “eta pairing”, Under normal electron band theory they ought to conduct electricity but they do not due to interactions among their electrons, What remains is to perform actual experiments with Mott insulators to verify that this process actually takes place   

    From RIKEN: “Light pulses provide a new route to enhance superconductivity” 

    RIKEN bloc

    From RIKEN

    March 4, 2019

    Chief Scientist
    Seiji Yunoki
    Computational Condensed Matter Physics Laboratory
    Chief Scientist Laboratories

    Jens Wilkinson
    RIKEN International Affairs Division
    Tel: +81-(0)48-462-1225 / Fax: +81-(0)48-463-3687
    Email: pr@riken.jp

    1
    Schematic of eta-pairing

    Materials known as Mott insulators are odd things. Under normal electron band theory they ought to conduct electricity, but they do not, due to interactions among their electrons. But now, scientists from the RIKEN Cluster for Pioneering Research have shown that pulses of light could be used to turn these materials beyond simple conductors to superconductors—materials that conduct electricity without energy loss. This process would happen through an unconventional type of superconductivity known as “eta pairing.”

    Using numerical simulations, the researchers found that this unconventional type of conductivity, which is believed to take place under non-equilibrium conditions in strongly correlated materials such as high-Tc cuprates and iron-pnictides, arises due to a phenomenon known as eta pairing. This is different form the superconductivity observed in the same strongly correlated materials under equilibrium conditions, and is thought to involve repulsive interactions between certain electrons within the structure. It is also different from traditional superconductivity, where the phenomenon arises due to interactions between electrons and vibrations of the crystal structure, inducing mutual interactions between electrons through vibrations and thus overcoming the repulsion between the electrons.

    Thirty years ago, the mathematical physicist Chen-Ning Yang originally proposed the idea of eta-pairing, but because it was a purely mathematical concept, it was understood as a virtual phenomenon that would not take place in the real world. But for the present study, the researchers used non-equilibrium dynamics to analyze the effect of pulses of light on a Mott insulator, and found that the effect would in fact happen in the real world. “What is interesting,” says first author Tatsuya Kaneko, a postdoctoral researcher at the RIKEN Cluster for Pioneering Research, “is that our calculations showed that this takes place based on the beautiful mathematical structure that Yang and his followers formulated so many years ago.”

    According to Seiji Yunoki, who led the research team, “This work provides new insights not only into the phenomenon of non-equilibrium dynamics, but also could lead to the development of new high-temperature superconductors, which could be useful in applications. What remains is to perform actual experiments with Mott insulators to verify that this process actually takes place.”

    The research was published in Physical Review Letters.

    See the full article here .


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    RIKEN is Japan’s largest comprehensive research institution renowned for high-quality research in a diverse range of scientific disciplines. Founded in 1917 as a private research foundation in Tokyo, RIKEN has grown rapidly in size and scope, today encompassing a network of world-class research centers and institutes across Japan.

     
  • richardmitnick 11:04 am on January 2, 2019 Permalink | Reply
    Tags: , , , , Physicists record “lifetime” of graphene qubits, , , superconductors   

    From MIT News: “Physicists record ‘lifetime’ of graphene qubits” 

    MIT News
    MIT Widget

    From MIT News

    December 31, 2018
    Rob Matheson

    1
    Researchers from MIT and elsewhere have recorded the “temporal coherence” of a graphene qubit — how long it maintains a special state that lets it represent two logical states simultaneously — marking a critical step forward for practical quantum computing. Stock image

    First measurement of its kind could provide stepping stone to practical quantum computing.

    Researchers from MIT and elsewhere have recorded, for the first time, the “temporal coherence” of a graphene qubit — meaning how long it can maintain a special state that allows it to represent two logical states simultaneously. The demonstration, which used a new kind of graphene-based qubit, represents a critical step forward for practical quantum computing, the researchers say.

    Superconducting quantum bits (simply, qubits) are artificial atoms that use various methods to produce bits of quantum information, the fundamental component of quantum computers. Similar to traditional binary circuits in computers, qubits can maintain one of two states corresponding to the classic binary bits, a 0 or 1. But these qubits can also be a superposition of both states simultaneously, which could allow quantum computers to solve complex problems that are practically impossible for traditional computers.

    The amount of time that these qubits stay in this superposition state is referred to as their “coherence time.” The longer the coherence time, the greater the ability for the qubit to compute complex problems.

    Recently, researchers have been incorporating graphene-based materials into superconducting quantum computing devices, which promise faster, more efficient computing, among other perks. Until now, however, there’s been no recorded coherence for these advanced qubits, so there’s no knowing if they’re feasible for practical quantum computing.

    In a paper published today in Nature Nanotechnology, the researchers demonstrate, for the first time, a coherent qubit made from graphene and exotic materials. These materials enable the qubit to change states through voltage, much like transistors in today’s traditional computer chips — and unlike most other types of superconducting qubits. Moreover, the researchers put a number to that coherence, clocking it at 55 nanoseconds, before the qubit returns to its ground state.

    The work combined expertise from co-authors William D. Oliver, a physics professor of the practice and Lincoln Laboratory Fellow whose work focuses on quantum computing systems, and Pablo Jarillo-Herrero, the Cecil and Ida Green Professor of Physics at MIT who researches innovations in graphene.

    “Our motivation is to use the unique properties of graphene to improve the performance of superconducting qubits,” says first author Joel I-Jan Wang, a postdoc in Oliver’s group in the Research Laboratory of Electronics (RLE) at MIT. “In this work, we show for the first time that a superconducting qubit made from graphene is temporally quantum coherent, a key requisite for building more sophisticated quantum circuits. Ours is the first device to show a measurable coherence time — a primary metric of a qubit — that’s long enough for humans to control.”

    There are 14 other co-authors, including Daniel Rodan-Legrain, a graduate student in Jarillo-Herrero’s group who contributed equally to the work with Wang; MIT researchers from RLE, the Department of Physics, the Department of Electrical Engineering and Computer Science, and Lincoln Laboratory; and researchers from the Laboratory of Irradiated Solids at the École Polytechnique and the Advanced Materials Laboratory of the National Institute for Materials Science.

    A pristine graphene sandwich

    Superconducting qubits rely on a structure known as a “Josephson junction,” where an insulator (usually an oxide) is sandwiched between two superconducting materials (usually aluminum). In traditional tunable qubit designs, a current loop creates a small magnetic field that causes electrons to hop back and forth between the superconducting materials, causing the qubit to switch states.

    But this flowing current consumes a lot of energy and causes other issues. Recently, a few research groups have replaced the insulator with graphene, an atom-thick layer of carbon that’s inexpensive to mass produce and has unique properties that might enable faster, more efficient computation.

    To fabricate their qubit, the researchers turned to a class of materials, called van der Waals materials — atomic-thin materials that can be stacked like Legos on top of one another, with little to no resistance or damage. These materials can be stacked in specific ways to create various electronic systems. Despite their near-flawless surface quality, only a few research groups have ever applied van der Waals materials to quantum circuits, and none have previously been shown to exhibit temporal coherence.

    For their Josephson junction, the researchers sandwiched a sheet of graphene in between the two layers of a van der Waals insulator called hexagonal boron nitride (hBN). Importantly, graphene takes on the superconductivity of the superconducting materials it touches. The selected van der Waals materials can be made to usher electrons around using voltage, instead of the traditional current-based magnetic field. Therefore, so can the graphene — and so can the entire qubit.

    When voltage gets applied to the qubit, electrons bounce back and forth between two superconducting leads connected by graphene, changing the qubit from ground (0) to excited or superposition state (1). The bottom hBN layer serves as a substrate to host the graphene. The top hBN layer encapsulates the graphene, protecting it from any contamination. Because the materials are so pristine, the traveling electrons never interact with defects. This represents the ideal “ballistic transport” for qubits, where a majority of electrons move from one superconducting lead to another without scattering with impurities, making a quick, precise change of states.

    How voltage helps

    The work can help tackle the qubit “scaling problem,” Wang says. Currently, only about 1,000 qubits can fit on a single chip. Having qubits controlled by voltage will be especially important as millions of qubits start being crammed on a single chip. “Without voltage control, you’ll also need thousands or millions of current loops too, and that takes up a lot of space and leads to energy dissipation,” he says.

    Additionally, voltage control means greater efficiency and a more localized, precise targeting of individual qubits on a chip, without “cross talk.” That happens when a little bit of the magnetic field created by the current interferes with a qubit it’s not targeting, causing computation problems.

    For now, the researchers’ qubit has a brief lifetime. For reference, conventional superconducting qubits that hold promise for practical application have documented coherence times of a few tens of microseconds, a few hundred times greater than the researchers’ qubit.

    But the researchers are already addressing several issues that cause this short lifetime, most of which require structural modifications. They’re also using their new coherence-probing method to further investigate how electrons move ballistically around the qubits, with aims of extending the coherence of qubits in general.

    See the full article here .


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  • richardmitnick 3:09 pm on January 16, 2014 Permalink | Reply
    Tags: , , , , superconductors   

    From Berkeley Lab: “Natural 3D Counterpart to Graphene Discovered” 


    Berkeley Lab

    Researchers at Berkeley Lab’s Advanced Light Source Find New Form of Quantum Matter

    January 16, 2014
    Lynn Yarris (510) 486-5375 lcyarris@lbl.gov

    The discovery of what is essentially a 3D version of graphene – the 2D sheets of carbon through which electrons race at many times the speed at which they move through silicon – promises exciting new things to come for the high-tech industry, including much faster transistors and far more compact hard drives. A collaboration of researchers at the U.S Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) has discovered that sodium bismuthate can exist as a form of quantum matter called a three-dimensional topological Dirac semi-metal (3DTDS). This is the first experimental confirmation of 3D Dirac fermions in the interior or bulk of a material, a novel state that was only recently proposed by theorists.

    graph
    A topological Dirac semi-metal state is realized at the critical point in the phase transition from a normal insulator to a topological insulator. The + and – signs denote the even and odd parity of the energy bands.

    “A 3DTDS is a natural three-dimensional counterpart to graphene with similar or even better electron mobility and velocity,” says Yulin Chen, a physicist with Berkeley Lab’s Advanced Light Source (ALS) when he initiated the study that led to this discovery, and now with the University of Oxford. “Because of its 3D Dirac fermions in the bulk, a 3DTDS also features intriguing non-saturating linear magnetoresistance that can be orders of magnitude higher than the materials now used in hard drives, and it opens the door to more efficient optical sensors.”

    Chen is the corresponding author of a paper in Science reporting the discovery. The paper is titled Discovery of a Three-dimensional Topological Dirac Semimetal, Na3Bi. Co-authors were Zhongkai Liu, Bo Zhou, Yi Zhang, Zhijun Wang, Hongming Weng, Dharmalingam Prabhakaran, Sung-Kwan Mo, Zhi-Xun Shen, Zhong Fang, Xi Dai and Zahid Hussain.

    See the full article and all of the excitment here.

    A U.S. Department of Energy National Laboratory Operated by the University of California

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