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  • richardmitnick 1:13 pm on November 12, 2020 Permalink | Reply
    Tags: "Advanced Atomic Clock Makes a Better Dark Matter Detector", , , JILA [Joint Institute for Laboratory Astrophysics/UColorado/NIST], NIST,   

    From NIST: “Advanced Atomic Clock Makes a Better Dark Matter Detector” 


    From NIST

    November 12, 2020
    Laura Ost
    laura.ost@nist.gov
    (303) 497-4880

    1
    Credit: N. Hanacek/NIST.

    JILA [Joint Institute for Laboratory Astrophysics/UColorado/NIST] researchers have used a state-of-the-art atomic clock to narrow the search for elusive dark matter, an example of how continual improvements in clocks have value beyond timekeeping.

    Older atomic clocks operating at microwave frequencies have hunted for dark matter before, but this is the first time a newer clock, operating at higher optical frequencies, and an ultra-stable oscillator to ensure steady light waves have been harnessed to set more precise bounds on the search. The research is described in Physical Review Letters.

    Astrophysical observations show that dark matter makes up most of the “stuff” in the universe, but so far it has eluded capture. Researchers around the world have been looking for it in various forms. The JILA team focused on ultralight dark matter, which in theory has a teeny mass (much less than a single electron) and a humongous wavelength — how far a particle spreads in space — that could be as large as the size of dwarf galaxies. This type of dark matter would be bound by gravity to galaxies and thus to ordinary matter.

    Ultralight dark matter is expected to create tiny fluctuations in two fundamental physical “constants”: the electron’s mass, and the fine-structure constant. The JILA team used a strontium lattice clock and a hydrogen maser (a microwave version of a laser) to compare their well-known optical and microwave frequencies, respectively, to the frequency of light resonating in an ultra-stable cavity made from a single crystal of pure silicon. The resulting frequency ratios are sensitive to variations over time in both constants. The relative fluctuations of the ratios and constants can be used as sensors to connect cosmological models of dark matter to accepted physics theories.

    The JILA team established new limits on a floor for “normal” fluctuations, beyond which any unusual signals discovered later might be due to dark matter. The researchers constrained the coupling strength of ultralight dark matter to the electron mass and the fine-structure constant to be on the order of 10^-5 (1 in 100,000) or less, the most precise measurement ever of this value.

    JILA is jointly operated by the National Institute of Standards and Technology (NIST) and the University of Colorado Boulder.

    “Nobody actually knows at what sensitivity level you will start to see dark matter in laboratory measurements,” NIST/JILA Fellow Jun Ye said. “The problem is that physics as we know it is not quite complete at this point. We know something is missing, but we don’t quite know how to fix it yet.”

    “We know dark matter exists from astrophysical observations, but we don’t know how the dark matter connects to ordinary matter and the values we measure,” Ye added. “Experiments like ours allow us to test various theory models people put together to try to explore the nature of dark matter. By setting better and better bounds, we hope to rule out some incorrect theory models and eventually make a discovery in the future.”

    Scientists are not sure whether dark matter consists of particles or oscillating fields affecting local environments, Ye noted. The JILA experiments are intended to detect dark matter’s “pulling” effect on ordinary matter and electromagnetic fields, he said.

    Atomic clocks are prime probes for dark matter because they can detect changes in fundamental constants and are rapidly improving in precision, stability and reliability. The cavity’s stability was also a crucial factor in the new measurements. The resonant frequency of light in the cavity depends on the length of the cavity, which can be traced back to the Bohr radius (a physical constant equal to the distance between the nucleus and the electron in a hydrogen atom). The Bohr radius is also related to the values of the fine-structure constant and electron mass. Therefore, changes in the resonant frequency as compared to transition frequencies in atoms can indicate fluctuations in these constants caused by dark matter.

    Researchers collected data on the strontium/cavity frequency ratio for 12 days with the clock running 30% of the time, resulting in a data set 978,041 seconds long. The hydrogen maser data spanned 33 days with the maser running 94% of the time, resulting in a 2,826,942-second record. The hydrogen/cavity frequency ratio provided useful sensitivity to the electron mass, although the maser was less stable and produced noisier signals than the strontium clock.

    JILA researchers collected the dark matter search data during their recent demonstration of an improved time scale — a system that incorporates data from multiple atomic clocks to produce a single, highly accurate timekeeping signal for distribution. As the performance of atomic clocks, optical cavities and time scales improves in the future, the frequency ratios can be reexamined with ever-higher resolution, further extending the reach of dark matter searches.

    “Any time one is running an optical atomic time scale, there is a chance to set a new bound on or make a discovery of dark matter,” Ye said. “In the future, when we can put these new systems in orbit, it will be the biggest ‘telescope’ ever built for the search for dark matter.”

    See the full article here.

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    NIST Campus, Gaitherberg, MD, USA

    NIST Mission, Vision, Core Competencies, and Core Values

    NIST’s mission

    To promote U.S. innovation and industrial competitiveness by advancing measurement science, standards, and technology in ways that enhance economic security and improve our quality of life.
    NIST’s vision

    NIST will be the world’s leader in creating critical measurement solutions and promoting equitable standards. Our efforts stimulate innovation, foster industrial competitiveness, and improve the quality of life.
    NIST’s core competencies

    Measurement science
    Rigorous traceability
    Development and use of standards

    NIST’s core values

    NIST is an organization with strong values, reflected both in our history and our current work. NIST leadership and staff will uphold these values to ensure a high performing environment that is safe and respectful of all.

    Perseverance: We take the long view, planning the future with scientific knowledge and imagination to ensure continued impact and relevance for our stakeholders.
    Integrity: We are ethical, honest, independent, and provide an objective perspective.
    Inclusivity: We work collaboratively to harness the diversity of people and ideas, both inside and outside of NIST, to attain the best solutions to multidisciplinary challenges.
    Excellence: We apply rigor and critical thinking to achieve world-class results and continuous improvement in everything we do.

     
  • richardmitnick 10:44 am on October 25, 2020 Permalink | Reply
    Tags: "A Billion Tiny Pendulums Could Detect the Universe’s Missing Mass", , , , NIST,   

    From NIST: “A Billion Tiny Pendulums Could Detect the Universe’s Missing Mass” 


    From NIST

    October 13, 2020

    Media Contact
    Ben P. Stein
    benjamin.stein@nist.gov
    (301) 975-2763

    Technical Contact
    Daniel Carney

    1
    Credit: NIST.

    Researchers at the National Institute of Standards and Technology (NIST) and their colleagues have proposed a novel method for finding Dark Matter*, the cosmos’s mystery material that has eluded detection for decades. Dark matter makes up about 27% of the universe; ordinary matter, such as the stuff that builds stars and planets, accounts for just 5% of the cosmos. (A mysterious entity called dark energy, accounts for the other 68%.)

    According to cosmologists, all the visible material in the universe is merely floating in a vast sea of dark matter — particles that are invisible but nonetheless have mass and exert a gravitational force. Dark matter’s gravity would provide the missing glue that keeps galaxies from falling apart and account for how matter clumped together to form the universe’s rich galactic tapestry.

    The proposed experiment, in which a billion millimeter-sized pendulums would act as dark matter sensors, would be the first to hunt for dark matter solely through its gravitational interaction with visible matter. The experiment would be one of the few to search for dark matter particles with a mass as great as that of a grain of salt, a scale rarely explored and never studied by sensors capable of recording tiny gravitational forces.


    Measuring the Mass of Dark Matter
    Dark matter, the hidden stuff of our universe, is notoriously difficult to detect. In search of direct evidence, NIST researchers have proposed using a 3D array of pendulums as force detectors, which could detect the gravitational influence of passing dark matter particles. When a dark matter particle is near a suspended pendulum, the pendulum should deflect slightly due to the attraction of both masses. However, this force is very small, and difficult to isolate from environmental noise that causes the pendulum to move. To better isolate the deflections from passing particles, NIST researchers propose using a pendulum array. Environmental noise affects each pendulum individually, causing them to move independently. However, particles passing through the array will produce correlated deflections of the pendulums. Because these movements are correlated, they can be isolated from the background noise, revealing how much force a particle delivers to each pendulum and the particle’s speed and direction, or velocity.

    Previous experiments have sought dark matter by looking for nongravitational signs of interactions between the invisible particles and certain kinds of ordinary matter. That’s been the case for searches for a hypothetical type of dark matter called the WIMP (weakly interacting massive particles), which was a leading candidate for the unseen material for more than two decades. Physicists looked for evidence that when WIMPs occasionally collide with chemical substances in a detector, they emit light or kick out electric charge.

    Researchers hunting for WIMPs in this way have either come up empty-handed or garnered inconclusive results; the particles are too light (theorized to range in mass between that of an electron and a proton) to detect through their gravitational tug.

    With the search for WIMPs seemingly on its last legs, researchers at NIST and their colleagues are now considering a more direct method to look for dark matter particles that have a heftier mass and therefore wield a gravitational force large enough to be detected.

    “Our proposal relies purely on the gravitational coupling, the only coupling we know for sure that exists between dark matter and ordinary luminous matter,” said study co-author Daniel Carney, a theoretical physicist jointly affiliated with NIST, the Joint Quantum Institute (JQI) and the Joint Center for Quantum Information and Computer Science (QuICS) at the University of Maryland in College Park, and the Fermi National Accelerator Laboratory.

    The researchers, who also include Jacob Taylor of NIST, JQI and QuICS; Sohitri Ghosh of JQI and QuICS; and Gordan Krnjaic of the Fermi National Accelerator Laboratory, calculate that their method can search for dark matter particles with a minimum mass about half that of a grain of salt, or about a billion billion times the mass of a proton. The scientists report their findings today in Physical Review D.

    Because the only unknown in the experiment is the mass of the dark matter particle, not how it couples to ordinary matter, “if someone builds the experiment we suggest, they either find dark matter or rule out all dark matter candidates over a wide range of possible masses,” said Carney. The experiment would be sensitive to particles ranging from about 1/5,000 of a milligram to a few milligrams.

    That mass scale is particularly interesting because it covers the so-called Planck mass, a quantity of mass determined solely by three fundamental constants of nature and equivalent to about 1/5,000 of a gram.

    Carney, Taylor and their colleagues propose two schemes for their gravitational dark matter experiment. Both involve tiny, millimeter-size mechanical devices acting as exquisitely sensitive gravitational detectors. The sensors would be cooled to temperatures just above absolute zero to minimize heat-related electrical noise and shielded from cosmic rays and other sources of radioactivity. In one scenario, a myriad of highly sensitive pendulums would each deflect slightly in response to the tug of a passing dark matter particle.

    Similar devices (with much larger dimensions) have already been employed in the recent Nobel-prize-winning detection of gravitational waves, ripples in the fabric of space-time predicted by Einstein’s theory of gravity. Carefully suspended mirrors, which act like pendulums, move less than the length of an atom in response to a passing gravitational wave.

    In another strategy, the researchers propose using spheres levitated by a magnetic field or beads levitated by laser light. In this scheme, the levitation is switched off as the experiment begins, so that the spheres or beads are in free fall. The gravity of a passing dark matter particle would ever so slightly disturb the path of the free-falling objects.

    “We are using the motion of objects as our signal,” said Taylor. “This is different from essentially every particle physics detector out there.”

    The researchers calculate that an array of about a billion tiny mechanical sensors distributed over a cubic meter is required to differentiate a true dark matter particle from an ordinary particle or spurious random electrical signals or “noise” triggering a false alarm in the sensors. Ordinary subatomic particles such as neutrons (interacting through a nongravitational force) would stop dead in a single detector. In contrast, scientists expect a dark matter particle, whizzing past the array like a miniature asteroid, would gravitationally jiggle every detector in its path, one after the other.

    Noise would cause individual detectors to move randomly and independently rather than sequentially, as a dark matter particle would. As a bonus, the coordinated motion of the billion detectors would reveal the direction the dark matter particle was headed as it zoomed through the array.

    To fabricate so many tiny sensors, the team suggests that researchers may want to borrow techniques that the smartphone and automotive industries already use to produce large numbers of mechanical detectors.

    Thanks to the sensitivity of the individual detectors, researchers employing the technology needn’t confine themselves to the dark side. A smaller-scale version of the same experiment could detect the weak forces from distant seismic waves as well as that from the passage of ordinary subatomic particles, such as neutrinos and single, low-energy photons (particles of light).

    The smaller-scale experiment could even hunt for dark matter particles — if they impart a large enough kick to the detectors through a nongravitational force, as some models predict, Carney said.

    “We are setting the ambitious target of building a gravitational dark matter detector, but the R&D needed to achieve that would open the door for many other detection and metrology measurements,” said Carney.

    *Dark Matter Background
    Fritz Zwicky discovered Dark Matter in the 1930s when observing the movement of the Coma Cluster., Vera Rubin a Woman in STEM denied the Nobel, did most of the work on Dark Matter.

    Fritz Zwicky from http:// palomarskies.blogspot.com.

    Coma cluster via NASA/ESA Hubble.

    In modern times, it was astronomer Fritz Zwicky, in the 1930s, who made the first observations of what we now call dark matter. His 1933 observations of the Coma Cluster of galaxies seemed to indicated it has a mass 500 times more than that previously calculated by Edwin Hubble. Furthermore, this extra mass seemed to be completely invisible. Although Zwicky’s observations were initially met with much skepticism, they were later confirmed by other groups of astronomers.

    Thirty years later, astronomer Vera Rubin provided a huge piece of evidence for the existence of dark matter. She discovered that the centers of galaxies rotate at the same speed as their extremities, whereas, of course, they should rotate faster. Think of a vinyl LP on a record deck: its center rotates faster than its edge. That’s what logic dictates we should see in galaxies too. But we do not. The only way to explain this is if the whole galaxy is only the center of some much larger structure, as if it is only the label on the LP so to speak, causing the galaxy to have a consistent rotation speed from center to edge.

    Vera Rubin, following Zwicky, postulated that the missing structure in galaxies is dark matter. Her ideas were met with much resistance from the astronomical community, but her observations have been confirmed and are seen today as pivotal proof of the existence of dark matter.

    Astronomer Vera Rubin at the Lowell Observatory in 1965, worked on Dark Matter (The Carnegie Institution for Science).


    Vera Rubin measuring spectra, worked on Dark Matter (Emilio Segre Visual Archives AIP SPL).


    Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970. https://home.dtm.ciw.edu.

    The Vera C. Rubin Observatory currently under construction on the El Peñón peak at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.

    LSST Data Journey, Illustration by Sandbox Studio, Chicago with Ana Kova.

    See the full article here.

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    NIST Campus, Gaitherberg, MD, USA

    NIST Mission, Vision, Core Competencies, and Core Values

    NIST’s mission

    To promote U.S. innovation and industrial competitiveness by advancing measurement science, standards, and technology in ways that enhance economic security and improve our quality of life.
    NIST’s vision

    NIST will be the world’s leader in creating critical measurement solutions and promoting equitable standards. Our efforts stimulate innovation, foster industrial competitiveness, and improve the quality of life.
    NIST’s core competencies

    Measurement science
    Rigorous traceability
    Development and use of standards

    NIST’s core values

    NIST is an organization with strong values, reflected both in our history and our current work. NIST leadership and staff will uphold these values to ensure a high performing environment that is safe and respectful of all.

    Perseverance: We take the long view, planning the future with scientific knowledge and imagination to ensure continued impact and relevance for our stakeholders.
    Integrity: We are ethical, honest, independent, and provide an objective perspective.
    Inclusivity: We work collaboratively to harness the diversity of people and ideas, both inside and outside of NIST, to attain the best solutions to multidisciplinary challenges.
    Excellence: We apply rigor and critical thinking to achieve world-class results and continuous improvement in everything we do.

     
  • richardmitnick 1:02 pm on September 16, 2020 Permalink | Reply
    Tags: "NIST Scientists Reveal the Power Behind the Curtain — With Neutrons", , Detecting electric fields in spaces that are unreachable by conventional probes, NIST, ,   

    From Sandia National Laboratories and NIST: “NIST Scientists Reveal the Power Behind the Curtain — With Neutrons” 

    From Sandia National Laboratories

    and


    National Institute of Standards and Technology

    1
    Neutrons (blue), which can penetrate solid objects (like a gray steel wall), have no electric charge. However, the magnetic spins of moving neutrons are affected by an electric field (green), experiencing a slight tweak to their spin direction as they pass through the field. This spin direction change (red angle) can be measured by polarimetry (using a neutron spin filter and solenoid, represented by the coil), offering a potential method for inspecting electrical devices that cannot be observed directly. Credit: N. Hanacek/NIST.

    In a potential step forward for imaging technology, scientists from the National Institute of Standards and Technology (NIST) and Sandia National Laboratories have developed a way to use neutrons to detect electric fields in spaces that are unreachable by conventional probes.

    Their nondestructive but penetrative method, described in the journal Physical Review Letters, could lead to sensing devices that can see through walls to detect the electric fields in electronic components — a clearly useful capability for security screening and other diagnostic applications.

    “This is the first time anyone has been able to image an electric field that has been physically isolated,” said Dan Hussey, a NIST physicist. “There could be something that you don’t want to disassemble but want to inspect. This approach might offer a way to see its electric fields even though barriers stand in the way.”

    The technique requires an intense beam of polarized neutrons, the particles that together with protons form the nuclei of all elements other than simple hydrogen. Neutrons possess the ability to penetrate dense materials, such as metals, which block the passage of other particles or types of radiation.

    Unlike charged particles, such as positively charged protons, neutrons possess no net electric charge. However, they do have a magnetic property called spin, which can be manipulated by a magnetic field. The neutron’s spin direction is affected by magnetism — something the research team used to their advantage.

    “The neutron is electrically neutral, and yet we’re using it to sense the electric field,” Hussey said.

    The idea originated with Sandia physicist Yuan-Yu Jau, who recently began a Laboratory Directed Research and Development (LDRD) project to detect electric fields in spaces unreachable by conventional probes. To realize it, Jau needed a good source of neutrons and capable detectors — needs that led him to the NIST Center for Neutron Research (NCNR).

    When a neutron passes through the electric field, it is equivalent to the electric field moving toward a stationary neutron; only the perspective, or frame of reference, is different. And when the source of an electric field moves, it generates a magnetic field.

    Even for the strong electric field employed in this demonstration experiment, the effective magnetic field was weak (about 50 times smaller than Earth’s magnetic field). Nevertheless, this weak magnetic field tilted the direction of the neutron’s magnetic spin slightly. In the experiments, the tilt angle was less than a degree, but using a sensitive polarimetry method developed by the team, a small rotation was measured with an accuracy of about one hundredth of a degree.

    To make this accurate measurement, Hussey and his NIST colleagues built on the NCNR’s established capabilities in polarimetry to develop a method that is about 100 times more sensitive than conventional polarimetry. Their method depends on the behavior of the neutrons’ spins as they pass into a type of electromagnet called a solenoid, used in conjunction with a polarized neutron spin filter. This device was developed for other purposes, but it proved ideal for this research.

    The conditions of the experiment might seem to undercut the practical value of the technique for use in the field, as the team required an inconveniently large reactor to generate the neutron beam. However, smaller, commercially available neutron generators do exist, suggesting that the method might one day be harnessed by portable equipment if it could generate a strong enough beam of neutrons.

    Hussey emphasized that the results demonstrate only that the concept is valid. “We didn’t leap ahead to trying to see inside metal objects, but that’s coming in the near future,” he said.

    However, the sensing technique could find more uses as researchers design experiments around it.

    “You might want to diagnose high-voltage electronics while they’re operating, or potentially study materials that have electric properties in sample environments,” Hussey said. “Now that the capability exists, perhaps other ideas will emerge.”

    See the full article here.

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    NIST Campus, Gaitherberg, MD, USA.

    NIST Mission, Vision, Core Competencies, and Core Values

    NIST’s mission

    To promote U.S. innovation and industrial competitiveness by advancing measurement science, standards, and technology in ways that enhance economic security and improve our quality of life.
    NIST’s vision

    NIST will be the world’s leader in creating critical measurement solutions and promoting equitable standards. Our efforts stimulate innovation, foster industrial competitiveness, and improve the quality of life.
    NIST’s core competencies

    Measurement science
    Rigorous traceability
    Development and use of standards

    NIST’s core values

    NIST is an organization with strong values, reflected both in our history and our current work. NIST leadership and staff will uphold these values to ensure a high performing environment that is safe and respectful of all.

    Perseverance: We take the long view, planning the future with scientific knowledge and imagination to ensure continued impact and relevance for our stakeholders.
    Integrity: We are ethical, honest, independent, and provide an objective perspective.
    Inclusivity: We work collaboratively to harness the diversity of people and ideas, both inside and outside of NIST, to attain the best solutions to multidisciplinary challenges.
    Excellence: We apply rigor and critical thinking to achieve world-class results and continuous improvement in everything we do.

    Sandia Campus.

    Sandia National Laboratory

    Sandia National Laboratories is a multiprogram laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration. With main facilities in Albuquerque, N.M., and Livermore, Calif., Sandia has major R&D responsibilities in national security, energy and environmental technologies, and economic competitiveness.



     
  • richardmitnick 9:07 am on August 18, 2020 Permalink | Reply
    Tags: AI Explainability, NIST   

    From NIST: “NIST Asks A.I. to Explain Itself” 


    From NIST

    August 18, 2020
    Chad Boutin
    charles.boutin@nist.gov
    (301) 975-4261

    Technical agency proposes four fundamental principles for judging how well AI decisions can be explained.


    Credit: B. Hayes/NIST

    It’s a question that many of us encounter in childhood: “Why did you do that?” As artificial intelligence (AI) begins making more consequential decisions that affect our lives, we also want these machines to be capable of answering that simple yet profound question. After all, why else would we trust AI’s decisions?

    This desire for satisfactory explanations has spurred scientists at the National Institute of Standards and Technology (NIST) to propose a set of principles by which we can judge how explainable AI’s decisions are. Their draft publication, Four Principles of Explainable Artificial Intelligence (Draft NISTIR 8312), is intended to stimulate a conversation about what we should expect of our decision-making devices.

    The report is part of a broader NIST effort to help develop trustworthy AI systems. NIST’s foundational research aims to build trust in these systems by understanding their theoretical capabilities and limitations and by improving their accuracy, reliability, security, robustness and explainability, which is the focus of this latest publication.

    The authors are requesting feedback on the draft from the public — and because the subject is a broad one, touching upon fields ranging from engineering and computer science to psychology and legal studies, they are hoping for a wide-ranging discussion.

    “AI is becoming involved in high-stakes decisions, and no one wants machines to make them without an understanding of why,” said NIST electronic engineer Jonathon Phillips, one of the report’s authors. “But an explanation that would satisfy an engineer might not work for someone with a different background. So, we want to refine the draft with a diversity of perspective and opinions.”

    An understanding of the reasons behind the output of an AI system can benefit everyone the output touches. If an AI contributes to a loan approval decision, for example, this understanding might help a software designer improve the system. But the applicant might want insight into the AI’s reasoning as well, either to understand why she was turned down, or, if she was approved, to help her continue acting in ways that maintain her good credit rating.

    According to the authors, the four principles for explainable AI are:

    -AI systems should deliver accompanying evidence or reasons for all their outputs.
    -Systems should provide explanations that are meaningful or understandable to individual users.
    -The explanation correctly reflects the system’s process for generating the output.
    -The system only operates under conditions for which it was designed or when the system reaches a sufficient confidence in its output. (The idea is that if a system has insufficient confidence in its decision, it should not supply a decision to the user.)

    While these principles are straightforward enough on the surface, Phillips said that individual users often have varied criteria for judging an AI’s success at meeting them. For instance, the second principle — how meaningful the explanation is — can imply different things to different people, depending on their role and connection to the job the AI is doing.

    “Think about Kirk and Spock and how each one talks,” Phillips said, referencing the Star Trek characters. “A doctor using an AI to help diagnose disease may only need Spock’s explanation of why the machine recommends a particular treatment, while the patient might be OK with less technical detail but want Kirk’s background on how it relates to his life.”

    Phillips and his co-authors align their concepts of explainable AI to relevant previous work in artificial intelligence, but they also compare the demands for explainability we place on our machines to those we place on our fellow humans. Do we measure up to the standards we are asking of AI? After exploring how human decisions hold up in light of the report’s four principles, the authors conclude that — spoiler alert — we don’t.

    “Human-produced explanations for our own choices and conclusions are largely unreliable,” they write, citing several examples. “Without conscious awareness, people incorporate irrelevant information into a variety of decisions from personality trait judgments to jury decisions.”

    However, our awareness of this apparent double standard could eventually help us better understand our own decisions and create a safer, more transparent world.

    “As we make advances in explainable AI, we may find that certain parts of AI systems are better able to meet societal expectations and goals than humans are,” said Phillips, whose past research indicates that collaborations between humans and AI can produce greater accuracy than either one working alone. “Understanding the explainability of both the AI system and the human opens the door to pursue implementations that incorporate the strengths of each.”

    For the moment, Phillips said, the authors hope the comments they receive advance the conversation.

    “I don’t think we know yet what the right benchmarks are for explainability,” he said. “At the end of the day we’re not trying to answer all these questions. We’re trying to flesh out the field so that discussions can be fruitful.”

    NIST is accepting comments on the draft until October 15, 2020; for more details, visit NIST’s webpage on AI explainability.

    See the full article here.

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    NIST Campus, Gaitherberg, MD, USA

    NIST Mission, Vision, Core Competencies, and Core Values

    NIST’s mission

    To promote U.S. innovation and industrial competitiveness by advancing measurement science, standards, and technology in ways that enhance economic security and improve our quality of life.
    NIST’s vision

    NIST will be the world’s leader in creating critical measurement solutions and promoting equitable standards. Our efforts stimulate innovation, foster industrial competitiveness, and improve the quality of life.
    NIST’s core competencies

    Measurement science
    Rigorous traceability
    Development and use of standards

    NIST’s core values

    NIST is an organization with strong values, reflected both in our history and our current work. NIST leadership and staff will uphold these values to ensure a high performing environment that is safe and respectful of all.

    Perseverance: We take the long view, planning the future with scientific knowledge and imagination to ensure continued impact and relevance for our stakeholders.
    Integrity: We are ethical, honest, independent, and provide an objective perspective.
    Inclusivity: We work collaboratively to harness the diversity of people and ideas, both inside and outside of NIST, to attain the best solutions to multidisciplinary challenges.
    Excellence: We apply rigor and critical thinking to achieve world-class results and continuous improvement in everything we do.

     
  • richardmitnick 4:17 pm on August 14, 2020 Permalink | Reply
    Tags: "A Light Bright and Tiny: NIST Scientists Build a Better Nanoscale LED", , , NIST, , The new device shows an increase in brightness of 100 to 1000 times over conventional tiny submicron-sized LED designs., Their tiny LED had actually become a tiny laser.   

    From NIST- “A Light Bright and Tiny: NIST Scientists Build a Better Nanoscale LED” 


    From NIST

    August 14, 2020
    Chad Boutin
    charles.boutin@nist.gov
    (301) 975-4261

    1
    Credit: B. Nikoobakht, N. Hanacek/NIST.

    A new design for light-emitting diodes (LEDs) developed by a team including scientists at the National Institute of Standards and Technology (NIST) may hold the key to overcoming a long-standing limitation in the light sources’ efficiency. The concept, demonstrated with microscopic LEDs in the lab, achieves a dramatic increase in brightness as well as the ability to create laser light — all characteristics that could make it valuable in a range of large-scale and miniaturized applications.

    The team, which also includes scientists from the University of Maryland, Rensselaer Polytechnic Institute and the IBM Thomas J. Watson Research Center, detailed its work in a paper published today in the peer-reviewed journal Science Advances. Their device shows an increase in brightness of 100 to 1,000 times over conventional tiny, submicron-sized LED designs.

    “It’s a new architecture for making LEDs,” said NIST’s Babak Nikoobakht, who conceived the new design. “We use the same materials as in conventional LEDs. The difference in ours is their shape.”

    LEDs have existed for decades, but the development of bright LEDs won a Nobel prize and ushered in a new era of lighting. However, even modern LEDs have a limitation that frustrates their designers. Up to a point, feeding an LED more electricity makes it shine more brightly, but soon the brightness drops off, making the LED highly inefficient. Called “efficiency droop” by the industry, the issue stands in the way of LEDs being used in a number of promising applications, from communications technology to killing viruses.

    While their novel LED design overcomes efficiency droop, the researchers did not initially set out to solve this problem. Their main goal was to create a microscopic LED for use in very small applications, such as the lab-on-a-chip technology that scientists at NIST and elsewhere are pursuing.

    The team experimented with a whole new design for the part of the LED that shines: Unlike the flat, planar design used in conventional LEDs, the researchers built a light source out of long, thin zinc oxide strands they refer to as fins. (Long and thin are relative terms: Each fin is only about 5 micrometers in length, stretching about a tenth of the way across an average human hair’s breadth.) Their fin array looks like a tiny comb that can extend to areas as large as 1 centimeter or more.

    “We saw an opportunity in fins, as I thought their elongated shape and large side facets might be able to receive more electrical current,” Nikoobakht said. “At first we just wanted to measure how much the new design could take. We started increasing the current and figured we’d drive it until it burned out, but it just kept getting brighter.”

    Their novel design shone brilliantly in wavelengths straddling the border between violet and ultraviolet, generating about 100 to 1,000 times as much power as typical tiny LEDs do. Nikoobakht characterizes the result as a significant fundamental discovery.

    “A typical LED of less than a square micrometer in area shines with about 22 nanowatts of power, but this one can produce up to 20 microwatts,” he said. “It suggests the design can overcome efficiency droop in LEDs for making brighter light sources.”

    “It’s one of the most efficient solutions I have seen,” said Grigory Simin, a professor of electrical engineering at the University of South Carolina who was not involved in the project. “The community has been working for years to improve LED efficiency, and other approaches often have technical issues when applied to submicrometer wavelength LEDs. This approach does the job well.”

    The team made another surprising discovery as they increased the current. While the LED shone in a range of wavelengths at first, its comparatively broad emission eventually narrowed to two wavelengths of intense violet color. The explanation grew clear: Their tiny LED had become a tiny laser.

    “Converting an LED into a laser takes a large effort. It usually requires coupling a LED to a resonance cavity that lets the light bounce around to make a laser,” Nikoobakht said. “It appears that the fin design can do the whole job on its own, without needing to add another cavity.”

    A tiny laser would be critical for chip-scale applications not only for chemical sensing, but also in next-generation hand-held communications products, high-definition displays and disinfection.

    “It’s got a lot of potential for being an important building block,” Nikoobakht said. “While this isn’t the smallest laser people have made, it’s a very bright one. The absence of efficiency droop could make it useful.”

    The research was supported in part by the U.S. Army Cooperative Research Agreement.

    See the full article here.

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    NIST Campus, Gaitherberg, MD, USA

    NIST Mission, Vision, Core Competencies, and Core Values

    NIST’s mission

    To promote U.S. innovation and industrial competitiveness by advancing measurement science, standards, and technology in ways that enhance economic security and improve our quality of life.
    NIST’s vision

    NIST will be the world’s leader in creating critical measurement solutions and promoting equitable standards. Our efforts stimulate innovation, foster industrial competitiveness, and improve the quality of life.
    NIST’s core competencies

    Measurement science
    Rigorous traceability
    Development and use of standards

    NIST’s core values

    NIST is an organization with strong values, reflected both in our history and our current work. NIST leadership and staff will uphold these values to ensure a high performing environment that is safe and respectful of all.

    Perseverance: We take the long view, planning the future with scientific knowledge and imagination to ensure continued impact and relevance for our stakeholders.
    Integrity: We are ethical, honest, independent, and provide an objective perspective.
    Inclusivity: We work collaboratively to harness the diversity of people and ideas, both inside and outside of NIST, to attain the best solutions to multidisciplinary challenges.
    Excellence: We apply rigor and critical thinking to achieve world-class results and continuous improvement in everything we do.

     
  • richardmitnick 11:13 am on June 22, 2020 Permalink | Reply
    Tags: "Comb on a Chip: New Design for ‘Optical Ruler’ Could Revolutionize Clocks; Telescopes; Telecommunications", , NIST, Optical microresonator,   

    From NIST and UCSB: “Comb on a Chip: New Design for ‘Optical Ruler’ Could Revolutionize Clocks, Telescopes, Telecommunications” 

    UC Santa Barbara Name bloc
    UC Santa Barbara


    From NIST

    June 22, 2020
    Media Contact

    Ben P. Stein
    benjamin.stein@nist.gov

    (301) 975-2763

    Technical Contact

    Gregory Moille
    gregory.moille@nist.gov

    (301) 975-8413

    1
    Credit: NIST

    Just as a meter stick with hundreds of tick marks can be used to measure distances with great precision, a device known as a laser frequency comb, with its hundreds of evenly spaced, sharply defined frequencies, can be used to measure the colors of light waves with great precision.

    Small enough to fit on a chip, miniature versions of these combs — so named because their set of uniformly spaced frequencies resembles the teeth of a comb — are making possible a new generation of atomic clocks, a great increase in the number of signals traveling through optical fibers, and the ability to discern tiny frequency shifts in starlight that hint at the presence of unseen planets. The newest version of these chip-based “microcombs,” created by researchers at the National Institute of Standards and Technology (NIST) and the University of California at Santa Barbara (UCSB), is poised to further advance time and frequency measurements by improving and extending the capabilities of these tiny devices.

    At the heart of these frequency microcombs lies an optical microresonator, a ring-shaped device about the width of a human hair in which light from an external laser races around thousands of times until it builds up high intensity. Microcombs, often made of glass or silicon nitride, typically require an amplifier for the external laser light, which can make the comb complex, cumbersome and costly to produce.

    The NIST scientists and their UCSB collaborators have demonstrated that microcombs created from the semiconductor aluminum gallium arsenide have two essential properties that make them especially promising. The new combs operate at such low power that they do not need an amplifier, and they can be manipulated to produce an extraordinarily steady set of frequencies — exactly what is needed to use the microchip comb as a sensitive tool for measuring frequencies with extraordinary precision. (The research is part of the NIST on a Chip program.)

    The newly developed microcomb technology can help enable engineers and scientists to make precision optical frequency measurements outside the laboratory, said NIST scientist Gregory Moille. In addition, the microcomb can be mass-produced through nanofabrication techniques similar to the ones already used to manufacture microelectronics.

    The researchers at UCSB led earlier efforts in examining microresonators composed of aluminum gallium arsenide. The frequency combs made from these microresonators require only one-hundredth the power of devices fabricated from other materials. However, the scientists had been unable to demonstrate a key property — that a discrete set of unwavering, or highly stable, frequencies could be generated from a microresonator made of this semiconductor.

    The NIST team tackled the problem by placing the microresonator within a customized cryogenic apparatus that allowed the researchers to probe the device at temperatures as low as 4 degrees above absolute zero. The low-temperature experiment revealed that the interaction between the heat generated by the laser light and the light circulating in the microresonator was the one and only obstacle preventing the device from generating the highly stable frequencies needed for successful operation.

    At low temperatures, the team demonstrated that it could reach the so-called soliton regime — where individual pulses of light that never change their shape, frequency or speed circulate within the microresonator. The researchers describe their work in the June issue of Laser and Photonics Reviews.

    With such solitons, all teeth of the frequency comb are in phase with each other, so that they can be used as a ruler to measure the frequencies employed in optical clocks, frequency synthesis, or laser-based distance measurements.

    Although some recently developed cryogenic systems are small enough that they could be used with the new microcomb outside the laboratory, the ultimate goal is to operate the device at room temperature. The new findings show that scientists will either have to quench or entirely avoid excess heating to achieve room-temperature operation.

    See the full article here.

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    NIST Campus, Gaitherberg, MD, USA

    NIST Mission, Vision, Core Competencies, and Core Values

    NIST’s mission

    To promote U.S. innovation and industrial competitiveness by advancing measurement science, standards, and technology in ways that enhance economic security and improve our quality of life.
    NIST’s vision

    NIST will be the world’s leader in creating critical measurement solutions and promoting equitable standards. Our efforts stimulate innovation, foster industrial competitiveness, and improve the quality of life.
    NIST’s core competencies

    Measurement science
    Rigorous traceability
    Development and use of standards

    NIST’s core values

    NIST is an organization with strong values, reflected both in our history and our current work. NIST leadership and staff will uphold these values to ensure a high performing environment that is safe and respectful of all.

    Perseverance: We take the long view, planning the future with scientific knowledge and imagination to ensure continued impact and relevance for our stakeholders.
    Integrity: We are ethical, honest, independent, and provide an objective perspective.
    Inclusivity: We work collaboratively to harness the diversity of people and ideas, both inside and outside of NIST, to attain the best solutions to multidisciplinary challenges.
    Excellence: We apply rigor and critical thinking to achieve world-class results and continuous improvement in everything we do.

     
  • richardmitnick 10:12 am on June 2, 2020 Permalink | Reply
    Tags: "Ebb and Flow: Creating Quantum Dots Automatically With AI", A precise control of quantum dots allows researchers to shuttle electrons around and modify their state; and in doing so perform information processing tasks., , , , It is particularly exciting to be involved in a research project aimed at development of fully autonomous tuning software., NIST, , , , Taking sensitive measurements to make sure that the dots have formed; that the number of electrons is just right; and that the dots can interact with one another., To transform quantum dot devices into functioning qubits in a research lab someone: usually a graduate student or postdoc has to carefully adjust voltages on all those gates .   

    From NIST: “Ebb and Flow: Creating Quantum Dots Automatically With AI” 


    From NIST

    June 2, 2020
    Justyna Zwolak

    1
    Credit: N. Hanacek/J. Zwolak/NIST

    Even though research on artificial intelligence (AI) goes back to the 1960s, it wasn’t until the past decade that AI really became an integral part of our lives. From automatically recognizing faces in our photo library to predicting traffic congestion and finding the fastest routes to our destination, AI is everywhere. It is also revolutionizing how research and science are being done, from data mining to drug discovery.

    What makes AI particularly attractive and at the same time really powerful is that it not only automates many laborious tasks — this in principle could be done with a well-written script — but learns how to do them from data alone, without ever being explicitly programmed to solve the problem at hand. This is known as training the AI.

    Think of tagging pictures: I thought it was really neat when my first “smart” photo album app not only highlighted faces of my friends and family members in pictures, but — after I tagged a couple of pictures with names — started suggesting (surprisingly accurately) when those people were in a new picture, even if their pose and facial expression were quite different from the already tagged pictures. At some point, my app even gave me the option to scan through all my pictures and tag all those people I had already identified. And did so really fast, considering the tens of thousands of pictures I had on my computer at that point! Now, whenever I take new pictures, my photo app matches any people in them to the people I have already tagged. And all I had to do was give the app just a couple of shots of each person to learn from: AI did the rest.

    In my research, I use an AI-powered face-recognition-like approach to classify “faces” of quantum dot devices for use as so-called qubits, the building blocks of a quantum computer’s processor. While in classical computers, information and processes are coded as strings of 0 (no signal in the circuit) and 1 (signal is on), quantum computers use 0, 1 and everything in between. This is achieved by replacing the classical 0-1 bits with quantum bits, aka qubits. There are certain mathematical problems, such as the factorization of numbers, in which quantum computers are expected to outperform classical ones.

    Controlling the Flow

    2
    Credit: N. Hanacek/J. Zwolak/NIST

    Quantum dots are one of the possible realizations of qubits. How do quantum dots work? Let’s conduct the following thought experiment: Suppose there are three locks on the Hudson River. Since the Hudson River can flow in both directions depending on the tide, by carefully adjusting the height of the locks we should be able to — at least in principle — control how much water flows between the reservoirs and chambers, and how much water gets trapped in the two chambers between the locks.

    For example, if all three locks were simultaneously brought up higher than the water level, there would be no water flow and the water levels in the two chambers should be approximately the same. If during the outgoing tide locks A and B were set high, and lock C brought down, we would lower the water level trapped in chamber BC below that in chamber AB. Conversely, if during the incoming tide we would lower lock A, the water levels would be reversed, i.e., the level of water trapped in chamber AB would be lower than in chamber BC. By playing with the heights of the locks we could achieve all possible combinations of the relative depths of chambers AB and BC (ignoring for a moment the actual effect of such locks on the changing tidal currents).

    This is quite like how quantum dots work, except that what flows is electric current, what is being trapped are individual electrons, and what is being raised and lowered is voltage applied to metallic gates imprinted above the electronic channels. A precise control of quantum dots allows researchers to shuttle electrons around and modify their state, and in doing so perform information processing tasks.

    Toward the Quantum Revolution

    Now, to transform quantum dot devices into functioning qubits in a research lab, someone, usually a graduate student or postdoc, has to carefully adjust voltages on all those gates and then take sensitive measurements to make sure that the dots have formed, that the number of electrons is just right, and that the dots can interact with one another. This requires the researcher to measure the current flowing through the device for a set of parameters, recognize what state the device is in from that measurement, change the gate voltages a bit, and then check the current again, repeating the process until the desired state is achieved. And the more dots (and gates) involved, the harder it is to tune all of them to work together properly.

    In fact, full automation of this process is one of the main obstacles to widespread use of semiconductor-based qubits. Even with semi-scripted tuning protocols, a lot of decisions about the proper parameters range are still made by the researcher. At the same time, as one of my colleagues, Jake Taylor, put it well, legions of graduate students applying “trial-and-error” approaches cannot be the ultimate answer for deploying quantum technologies. To enable the quantum revolution, we need to find a way to take the human out of the picture.

    This is the goal of our work. Using the mathematics of pattern recognition and classical optimization, we are developing an auto-tuning protocol that doesn’t require a human to navigate between quantum dot states in real time. The AI in our protocol works like the face recognition app on a phone — whenever a new measurement is taken, it analyzes it and returns a prediction of the most likely state of the device. That information is then fed into an optimization routine that, based on what has been seen so far, suggests how the voltages should be adjusted for the next measurement and— with each iteration — tries to get closer and closer to the desired state, tuning the quantum dot device in the process.

    To train the AI, one of my colleagues, Sandesh Kalantre of the University of Maryland, has developed a model that generates large sets of images of simulated measurements, just like the ones we see in the lab. This was an extremely important step, as a large volume of data is necessary to train the AI.

    In light of the recent advances in building larger quantum dot arrays, it is particularly exciting to be involved in a research project aimed at development of fully autonomous tuning software. However, even though the numerous attempts to automate the various steps of the tuning process — using a combination of image processing, pattern matching, and machine learning — bring us much closer to this goal than ever before, full automation is yet to be achieved. Still, our work is not only paving a path forward for experiments with a larger number of quantum dots, but will also allow us to allocate more precious time — and graduate students — to do more stimulating research.

    See the full article here.

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    NIST Campus, Gaitherberg, MD, USA

    NIST Mission, Vision, Core Competencies, and Core Values

    NIST’s mission

    To promote U.S. innovation and industrial competitiveness by advancing measurement science, standards, and technology in ways that enhance economic security and improve our quality of life.
    NIST’s vision

    NIST will be the world’s leader in creating critical measurement solutions and promoting equitable standards. Our efforts stimulate innovation, foster industrial competitiveness, and improve the quality of life.
    NIST’s core competencies

    Measurement science
    Rigorous traceability
    Development and use of standards

    NIST’s core values

    NIST is an organization with strong values, reflected both in our history and our current work. NIST leadership and staff will uphold these values to ensure a high performing environment that is safe and respectful of all.

    Perseverance: We take the long view, planning the future with scientific knowledge and imagination to ensure continued impact and relevance for our stakeholders.
    Integrity: We are ethical, honest, independent, and provide an objective perspective.
    Inclusivity: We work collaboratively to harness the diversity of people and ideas, both inside and outside of NIST, to attain the best solutions to multidisciplinary challenges.
    Excellence: We apply rigor and critical thinking to achieve world-class results and continuous improvement in everything we do.

     
  • richardmitnick 12:47 pm on May 11, 2020 Permalink | Reply
    Tags: "NIST Scientists Create New Recipe for Single-Atom Transistors", NIST, ,   

    From NIST: “NIST Scientists Create New Recipe for Single-Atom Transistors” 


    From NIST

    May 11, 2020

    Media Contact
    Ben P. Stein
    benjamin.stein@nist.gov
    (301) 975-2763

    Technical Contact
    Richard M. Silver
    richard.silver@nist.gov
    (301) 975-5609

    1
    Credit: S. Kelley/NIST

    Once unimaginable, transistors consisting only of several-atom clusters or even single atoms promise to become the building blocks of a new generation of computers with unparalleled memory and processing power. But to realize the full potential of these tiny transistors — miniature electrical on-off switches — researchers must find a way to make many copies of these notoriously difficult-to-fabricate components.

    Now, researchers at the National Institute of Standards and Technology (NIST) and their colleagues at the University of Maryland have developed a step-by-step recipe to produce the atomic-scale devices. Using these instructions, the NIST-led team has become only the second in the world to construct a single-atom transistor and the first to fabricate a series of single electron transistors with atom-scale control over the devices’ geometry.

    The scientists demonstrated that they could precisely adjust the rate at which individual electrons flow through a physical gap or electrical barrier in their transistor — even though classical physics would forbid the electrons from doing so because they lack enough energy. That strictly quantum phenomenon, known as quantum tunneling, only becomes important when gaps are extremely tiny, such as in the miniature transistors. Precise control over quantum tunneling is key because it enables the transistors to become “entangled” or interlinked in a way only possible through quantum mechanics and opens new possibilities for creating quantum bits (qubits) that could be used in quantum computing.

    To fabricate single-atom and few-atom transistors, the team relied on a known technique in which a silicon chip is covered with a layer of hydrogen atoms, which readily bind to silicon. The fine tip of a scanning tunneling microscope then removed hydrogen atoms at selected sites. The remaining hydrogen acted as a barrier so that when the team directed phosphine gas (PH3) at the silicon surface, individual PH3 molecules attached only to the locations where the hydrogen had been removed (see animation). The researchers then heated the silicon surface. The heat ejected hydrogen atoms from the PH3 and caused the phosphorus atom that was left behind to embed itself in the surface. With additional processing, bound phosphorous atoms created the foundation of a series of highly stable single- or few-atom devices that have the potential to serve as qubits.

    Two of the steps in the method devised by the NIST teams — sealing the phosphorus atoms with protective layers of silicon and then making electrical contact with the embedded atoms — appear to have been essential to reliably fabricate many copies of atomically precise devices, NIST researcher Richard Silver said.

    In the past, researchers have typically applied heat as all the silicon layers are grown, in order to remove defects and ensure that the silicon has the pure crystalline structure required to integrate the single-atom devices with conventional silicon-chip electrical components. But the NIST scientists found that such heating could dislodge the bound phosphorus atoms and potentially disrupt the structure of the atomic-scale devices. Instead, the team deposited the first several silicon layers at room temperature, allowing the phosphorus atoms to stay put. Only when subsequent layers were deposited did the team apply heat.

    “We believe our method of applying the layers provides more stable and precise atomic-scale devices,“ said Silver. Having even a single atom out of place can alter the conductivity and other properties of electrical components that feature single or small clusters of atoms.

    The team also developed a novel technique for the crucial step of making electrical contact with the buried atoms so that they can operate as part of a circuit. The NIST scientists gently heated a layer of palladium metal applied to specific regions on the silicon surface that resided directly above selected components of the silicon-embedded device. The heated palladium reacted with the silicon to form an electrically conducting alloy called palladium silicide, which naturally penetrated through the silicon and made contact with the phosphorus atoms.

    In a recent edition of Advanced Functional Materials, Silver and his colleagues, who include Xiqiao Wang, Jonathan Wyrick, Michael Stewart Jr. and Curt Richter, emphasized that their contact method has a nearly 100% success rate. That’s a key achievement, noted Wyrick. “You can have the best single-atom-transistor device in the world, but if you can’t make contact with it, it’s useless,” he said.

    Fabricating single-atom transistors “is a difficult and complicated process that maybe everyone has to cut their teeth on, but we’ve laid out the steps so that other teams don’t have to proceed by trial and error,” said Richter.

    In related work published today in Communications Physics, Silver and his colleagues demonstrated that they could precisely control the rate at which individual electrons tunnel through atomically precise tunnel barriers in single-electron transistors. The NIST researchers and their colleagues fabricated a series of single-electron transistors identical in every way except for differences in the size of the tunneling gap. Measurements of current flow indicated that by increasing or decreasing the gap between transistor components by less than a nanometer (billionth of a meter), the team could precisely control the flow of a single electron through the transistor in a predictable manner.

    “Because quantum tunneling is so fundamental to any quantum device, including the construction of qubits, the ability to control the flow of one electron at a time is a significant achievement,” Wyrick said. In addition, as engineers pack more and more circuitry on a tiny computer chip and the gap between components continues to shrink, understanding and controlling the effects of quantum tunneling will become even more critical, Richter said.

    See the full article here.

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    NIST Campus, Gaitherberg, MD, USA

    NIST Mission, Vision, Core Competencies, and Core Values

    NIST’s mission

    To promote U.S. innovation and industrial competitiveness by advancing measurement science, standards, and technology in ways that enhance economic security and improve our quality of life.
    NIST’s vision

    NIST will be the world’s leader in creating critical measurement solutions and promoting equitable standards. Our efforts stimulate innovation, foster industrial competitiveness, and improve the quality of life.
    NIST’s core competencies

    Measurement science
    Rigorous traceability
    Development and use of standards

    NIST’s core values

    NIST is an organization with strong values, reflected both in our history and our current work. NIST leadership and staff will uphold these values to ensure a high performing environment that is safe and respectful of all.

    Perseverance: We take the long view, planning the future with scientific knowledge and imagination to ensure continued impact and relevance for our stakeholders.
    Integrity: We are ethical, honest, independent, and provide an objective perspective.
    Inclusivity: We work collaboratively to harness the diversity of people and ideas, both inside and outside of NIST, to attain the best solutions to multidisciplinary challenges.
    Excellence: We apply rigor and critical thinking to achieve world-class results and continuous improvement in everything we do.

     
  • richardmitnick 11:42 am on February 24, 2020 Permalink | Reply
    Tags: "A Simple Retrofit Transforms Ordinary Electron Microscopes Into High-Speed Atom-Scale Cameras", , , NIST   

    From NIST: “A Simple Retrofit Transforms Ordinary Electron Microscopes Into High-Speed Atom-Scale Cameras” 


    From NIST

    February 24, 2020

    Ben P. Stein
    benjamin.stein@nist.gov
    (301) 975-2763

    Patented “beam chopper” provides cost-effective way to investigate super-fast processes important for tomorrow’s technology.

    1
    Credit: N. Hanacek/NIST

    Researchers at the National Institute of Standards and Technology (NIST) and their collaborators have developed a way to retrofit the transmission electron microscope — a long-standing scientific workhorse for making crisp microscopic images — so that it can also create high-quality movies of super-fast processes at the atomic and molecular scale. Compatible with electron microscopes old and new, the retrofit promises to enable fresh insights into everything from microscopic machines to next-generation computer chips and biological tissue by making this moviemaking capability more widely available to laboratories everywhere.

    “We want to be able to look at things in materials science that happen really quickly,” said NIST scientist June Lau. She reports the first proof-of-concept operation of this retrofitted design with her colleagues in the journal Review of Scientific Instruments. The team designed the retrofit to be a cost-effective add-on to existing instruments. “It’s expected to be a fraction of the cost of a new electron microscope,” she said.

    A nearly 100-year-old invention, the electron microscope remains an essential tool in many scientific laboratories. A popular version is known as the transmission electron microscope (TEM), which fires electrons through a target sample to produce an image. Modern versions of the microscope can magnify objects by as much as 50 million times. Electron microscopes have helped to determine the structure of viruses, test the operation of computer circuits, and reveal the effectiveness of new drugs.

    “Electron microscopes can look at very tiny things on the atomic scale,” Lau said. “They are great. But historically, they look at things that are fixed in time. They’re not good at viewing moving targets,” she said.

    In the last 15 years, laser-assisted electron microscopes made videos possible, but such systems have been complex and expensive. While these setups can capture events that last from nanoseconds (billionths of a second) to femtoseconds (quadrillionths of a second), a laboratory must often buy a newer microscope to accommodate this capability as well as a specialized laser, with a total investment that can run into the millions of dollars. A lab also needs in-house laser-physics expertise to help set up and operate such a system.

    “Frankly, not everyone has that capacity,” Lau said.

    In contrast, the retrofit enables TEMs of any age to make high-quality movies on the scale of picoseconds (trillionths of a second) by using a relatively simple “beam chopper.” In principle, the beam chopper can be used in any manufacturer’s TEM. To install it, NIST researchers open the microscope column directly under the electron source, insert the beam chopper and close up the microscope again. Lau and her colleagues have successfully retrofitted three TEMs of different capabilities and vintage.

    Like a stroboscope, this beam chopper releases precisely timed pulses of electrons that can capture frames of important repeating or cyclic processes.

    “Imagine a Ferris wheel, which moves in a cyclical and repeatable way,” Lau said. “If we’re recording it with a pinhole camera, it will look blurry. But we want to see individual cars. I can put a shutter in front of the pinhole camera so that the shutter speed matches the movement of the wheel. We can time the shutter to open whenever a designated car goes to the top. In this way I can make a stack of images that shows each car at the top of the Ferris wheel,” she said.

    Like the light shutter, the beam chopper interrupts a continuous electron beam. But unlike the shutter, which has an aperture that opens and closes, this beam aperture stays open all the time, eliminating the need for a complex mechanical part.

    Instead, the beam chopper generates a radio frequency (RF) electromagnetic wave in the direction of the electron beam. The wave causes the traveling electrons to behave “like corks bobbing up and down on the surface of a water wave,” Lau said.

    Riding this wave, the electrons follow an undulating path as they approach the aperture. Most electrons are blocked except for the ones that are perfectly aligned with the aperture. The frequency of the RF wave is tunable, so that electrons hit the sample anywhere from 40 million to 12 billion times per second. As a result, researchers can capture important processes in the sample at time intervals from about a nanosecond to 10 picoseconds.

    In this way, the NIST-retrofitted microscope can capture atom-scale details of the back-and-forth movements in tiny machines such as microelectromechanical systems (MEMS) and nanoelectromechanical systems (NEMS). It can potentially study the regularly repeating signals in antennas used for high-speed communications and probe the movement of electric currents in next-generation computer processors.

    In one demo, the researchers wanted to prove that a retrofitted microscope functioned as it did before the retrofit. They imaged gold nanoparticles in both the traditional “continuous” mode and the pulsed beam mode. The images in the pulsed mode had comparable clarity and resolution to the still images.

    “We designed it so it should be the same,” Lau said.

    2
    A transmission electron microscope (TEM) image of gold (Au) nanoparticles magnified 200,000 times with a continuous electron beam (left) and a pulsed beam (right). The scale is 5 nanometers (nm).

    The beam chopper can also do double duty, pumping RF energy into the material sample and then taking pictures of the results. The researchers demonstrated this ability by injecting microwaves (a form of radio wave) into a metallic, comb-shaped MEMS device. The microwaves create electric fields within the MEMS device and cause the incoming pulses of electrons to deflect. These electron deflections enable researchers to build movies of the microwaves propagating through the MEMS comb.

    Lau and her colleagues hope their invention can soon make new scientific discoveries. For example, it could investigate the behavior of quickly changing magnetic fields in molecular-scale memory devices that promise to store more information than before.

    The researchers spent six years inventing and developing their beam chopper and have received several patents and an R&D 100 Award for their work. Co-authors in the work included Brookhaven National Laboratory in Upton, New York, and Euclid Techlabs in Bolingbrook, Illinois.

    One of the things that makes Lau most proud is that their design can breathe new life into any TEM, including the 25-year-old unit that performed the latest demonstration. The design gives labs everywhere the potential to use their microscopes to capture important fast-moving processes in tomorrow’s materials.

    “Democratizing science was the whole motivation,” Lau said.

    See the full article here.

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    NIST Campus, Gaitherberg, MD, USA

    NIST Mission, Vision, Core Competencies, and Core Values

    NIST’s mission

    To promote U.S. innovation and industrial competitiveness by advancing measurement science, standards, and technology in ways that enhance economic security and improve our quality of life.
    NIST’s vision

    NIST will be the world’s leader in creating critical measurement solutions and promoting equitable standards. Our efforts stimulate innovation, foster industrial competitiveness, and improve the quality of life.
    NIST’s core competencies

    Measurement science
    Rigorous traceability
    Development and use of standards

    NIST’s core values

    NIST is an organization with strong values, reflected both in our history and our current work. NIST leadership and staff will uphold these values to ensure a high performing environment that is safe and respectful of all.

    Perseverance: We take the long view, planning the future with scientific knowledge and imagination to ensure continued impact and relevance for our stakeholders.
    Integrity: We are ethical, honest, independent, and provide an objective perspective.
    Inclusivity: We work collaboratively to harness the diversity of people and ideas, both inside and outside of NIST, to attain the best solutions to multidisciplinary challenges.
    Excellence: We apply rigor and critical thinking to achieve world-class results and continuous improvement in everything we do.

     
  • richardmitnick 9:54 am on November 19, 2019 Permalink | Reply
    Tags: "NIST’s Light-Sensing Camera May Help Detect Extraterrestrial Life, , , NIST,   

    From NIST: “NIST’s Light-Sensing Camera May Help Detect Extraterrestrial Life, Dark Matter” 


    From NIST

    November 19, 2019
    Laura Ost
    laura.ost@nist.gov
    (303) 497-4880

    1
    Credit: V. Verma/NIST

    Researchers at the National Institute of Standards and Technology (NIST) have made one of the highest-performance cameras ever composed of sensors that count single photons, or particles of light.

    With more than 1,000 sensors, or pixels, NIST’s camera may be useful in future space-based telescopes searching for chemical signs of life on other planets, and in new instruments designed to search for the elusive “dark matter” believed to constitute most of the “stuff” in the universe.

    Described in Optics Express, the camera consists of sensors made from superconducting nanowires, which can detect single photons. They are among the best photon counters in terms of speed, efficiency, and range of color sensitivity. A NIST team used these detectors to demonstrate Einstein’s “spooky action at a distance,” for example.

    The nanowire detectors also have the lowest dark count rates of any type of photon sensor, meaning they don’t count false signals caused by noise rather than photons. This feature is especially useful for dark-matter searches and space-based astronomy. But cameras with more pixels and larger physical dimensions than previously available are required for these applications, and they also need to detect light at the far end of the infrared band, with longer wavelengths than currently practical.

    NIST’s camera is small in physical size, a square measuring 1.6 millimeters on a side, but packed with 1,024 sensors (32 columns by 32 rows) to make high-resolution images. The main challenge was to find a way to collate and obtain results from so many detectors without overheating. The researchers extended a “readout” architecture they previously demonstrated with a smaller camera of 64 sensors that adds up data from the rows and columns, a step toward meeting the requirements of the National Aeronautics and Space Administration (NASA).

    “My primary motivation for making the camera is NASA’s Origins Space Telescope project, which is looking into using these arrays for analyzing the chemical composition of planets orbiting stars outside of our solar system,” NIST electronics engineer Varun Verma said. Each chemical element in the planet’s atmosphere would absorb a unique set of colors, he pointed out.

    “The idea is to look at the absorption spectra of light passing through the edge of an exoplanet’s atmosphere as it transits in front of its parent star,” Verma explained. “The absorption signatures tell you about the elements in the atmosphere, particularly those that might give rise to life, such as water, oxygen and carbon dioxide. The signatures for these elements are in the mid- to far-infrared spectrum, and large-area single-photon counting detector arrays don’t yet exist for that region of the spectrum, so we received a small amount of funding from NASA to see if we could help solve that problem.”

    Verma and colleagues achieved high fabrication success, with 99.5% of the sensors working properly. But detector efficiency at the desired wavelength is low. Boosting efficiency is the next challenge. The researchers also hope to make even bigger cameras, perhaps with a million sensors.

    Other applications are also possible. For example, the NIST cameras may help find dark matter. Researchers around the world have been unable to find so-called weakly interacting massive particles (WIMPs) and are considering looking for dark matter with lower energy and mass. Superconducting nanowire detectors offer promise for counting emissions of rare, low-energy dark matter and discriminating real signals from background noise.

    The new camera was made in a complicated process at NIST’s Microfabrication Facility in Boulder, Colorado. The detectors are fabricated on silicon wafers diced into chips. The nanowires, made of an alloy of tungsten and silicon, are about 3.5 millimeters long, 180 nanometers (nm) wide and 3 nm thick. The wiring is made of superconducting niobium.

    The camera performance was measured by the Jet Propulsion Laboratory (JPL) at the California Institute of Technology in Pasadena, California. JPL has the necessary electronics due to its work on deep space optical communications.

    The work was supported by NASA and the Defense Advanced Research Projects Agency.

    See the full article here.

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