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  • richardmitnick 2:29 pm on April 1, 2020 Permalink | Reply
    Tags: "To Tune Up Your Quantum Computer Better Call an AI Mechanic", , NIST - National Institute of Standards and Technology   

    From NIST: “To Tune Up Your Quantum Computer, Better Call an AI Mechanic” 


    From NIST

    March 31, 2020

    Chad Boutin
    charles.boutin@nist.gov
    (301) 975-4261

    New paradigm for “auto-tuning” quantum bits could overcome major engineering hurdle.

    1
    Credit: B. Hayes/NIST
    This artist’s conception shows how the research team used artificial intelligence (AI) and other computational techniques to tune a quantum dot device for use as a qubit. The dot’s electrons are corralled by electrical gates, whose adjustable voltages raise and lower the “peaks” and “valleys” in the large circles. As the gates push the electrons around, sensitive measurement of the moving electrons creates telltale lines in the black and white images, which the AI uses to judge the state of the dot and then make successive adjustments to the gate voltages. Eventually the AI converts a single dot (leftmost large circle) to a double dot (rightmost), a process that takes tedious hours for a human operator.

    A high-end race car engine needs all its components tuned and working together precisely to deliver top-quality performance. The same can be said about the processor inside a quantum computer, whose delicate bits must be adjusted in just the right way before it can perform a calculation. Who’s the right mechanic for this quantum tuneup job? According to a team that includes scientists at the National Institute of Standards and Technology (NIST), it’s an artificial intelligence, that’s who.

    The team’s paper in the journal Physical Review Applied outlines a way to teach an AI to make an interconnected set of adjustments to tiny quantum dots, which are among the many promising devices for creating the quantum bits, or “qubits,” that would form the switches in a quantum computer’s processor.

    Precisely tweaking the dots is crucial for transforming them into properly functioning qubits, and until now the job had to be done painstakingly by human operators, requiring hours of work to create even a small handful of qubits for a single calculation.

    A practical quantum computer with many interacting qubits would require far more dots — and adjustments — than a human could manage, so the team’s accomplishment might bring quantum dot-based processing closer from the realm of theory to engineered reality.

    “Quantum computer theorists imagine what they could do with hundreds or thousands of qubits, but the elephant in the room is that we can actually make only a handful of them work at a time,” said Justyna Zwolak, a NIST mathematician. “Now we have a path forward to making this real.”

    A quantum dot typically contains electrons that are confined to a tight boxlike space in a semiconductor material. Forming the box’s walls are several metallic electrodes (so-called gates) above the semiconductor surface that have electric voltage applied to them, influencing the quantum dot’s position and number of electrons. Depending on their position relative to the dot, the gates control the electrons in different ways.

    To make the dots do what you want — act as one sort of qubit logic switch or another, for example — the gate voltages must be tuned to just the right values. This tuning is done manually, by measuring currents flowing through the quantum dot system, then changing the gate voltages a bit, then checking the current again. And the more dots (and gates) you involve, the harder it is to tune them all simultaneously so that you get qubits that work together properly.

    In short, this isn’t a gig that any human mechanic would feel bad about losing to a machine.

    “It’s usually a job done by a graduate student,” said graduate student Tom McJunkin of the University of Wisconsin-Madison’s physics department and a co-author on the paper. “I could tune one dot in a few hours, and two might take a day of twiddling knobs. I could do four, but not if I need to go home and sleep. As this field grows, we can’t spend weeks getting the system ready — we need to take the human out of the picture.”

    Pictures, though, are just what McJunkin was used to looking at while tuning the dots: The data he worked with came in the form of visual images, which the team realized that AI is good at recognizing. AI algorithms called convolutional neural networks have become the go-to technique for automated image classification, as long as they are exposed to lots of examples of what they need to recognize. So the team’s Sandesh Kalantre, under supervision from Jake Taylor at the Joint Quantum Institute, created a simulator that would generate thousands of images of quantum dot measurements they could feed to the AI as a training exercise.

    “We simulate the qubit setup we want and run it overnight, and in the morning we have all the data we need to train the AI to tune the system automatically,” Zwolak said. “And we designed it to be usable on any quantum dot-based system, not just our own.”

    The team started small, using a setup of two quantum dots, and they verified that within certain constraints their trained AI could auto-tune the system to the setup they desired. It wasn’t perfect — they identified several areas they need to work on to improve the approach’s reliability — and they can’t use it to tune thousands of interconnected quantum dots as yet. But even at this early stage its practical power is undeniable, allowing a skilled researcher to spend valuable time elsewhere.

    “It’s a way to use machine learning to save labor, and — eventually — to do something that human beings aren’t good at doing,” Zwolak said. “We can all recognize a three-dimensional cat, and that’s basically what a single dot with a few properly-tuned gates is. Lots of dots and gates are like a 10-dimensional cat. A human can’t even see a 10D cat. But we can train an AI to recognize one.”

    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 8:53 am on January 20, 2020 Permalink | Reply
    Tags: "Precise measurements find a crack in universal physics", "Van der Waals universality", , Efimov physics, Efimov trimers-Strong two-body interactions can mediate three-body attraction and form weakly bound three-body states., Efimov trimers-The researchers discovered Efimov trimers with sizes that are significantly larger than what the universal theory predicts., NIST - National Institute of Standards and Technology, , , Ultracold atomic systems   

    From NIST via phys.org: “Precise measurements find a crack in universal physics” 


    From NIST

    via


    phys.org

    January 15, 2020
    Ingrid Fadelli

    1
    A photo of the experimental setup used for performing precise studies of universal physics in an ultracold atomic sample. A myriad of elements (including lasers, optical components, magnetic field coils, and RF antennas) are used for capturing atoms from a hot (around 400 Kelvin) potassium vapor source (the chamber shown in top right), cooling the gas sample to ultracold temperatures (around 10^-8 Kelvin) in the ultrahigh vacuum chamber (top left), manipulating the quantum states, performing precision spectroscopy, and imaging of ultracold clouds. Figure credit: Roman Chapurin.

    The concept of universal physics is intriguing, as it enables researchers to relate physical phenomena in a variety of systems, irrespective of their varying characteristics and complexities. Ultracold atomic systems are often perceived as ideal platforms for exploring universal physics, owing to the precise control of experimental parameters (such as the interaction strength, temperature, density, quantum states, dimensionality, and the trapping potential) that might be harder to tune in more conventional systems. In fact, ultracold atomic systems have been used to better understand a myriad of complex physical behavior, including those topics in cosmology, particle, nuclear, molecular physics, and most notably, in condensed matter physics, where the complexities of many-body quantum phenomena are more difficult to investigate using more traditional approaches.

    Understanding the applicability and the robustness of universal physics is thus of great interest. Researchers at the National Institute of Standards and Technology (NIST) and the University of Colorado Boulder have carried out a study, recently featured in Physical Review Letters, aimed at testing the limits to universality in an ultracold system.

    “Unlike in other physical systems, the beauty of ultracold systems is that at times we are able to scrap the importance of the periodic table and demonstrate the similar phenomenon with any chosen atomic species (be it potassium, rubidium, lithium, strontium, etc.),” Roman Chapurin, one of the researchers who carried out the study, told Phys.org. “Universal behavior is independent of the microscopic details. Understanding the limitations of universal phenomenon is of great interest.”

    Due to the few-body nature of interactions in most ultracold systems, researchers must attain a better knowledge of few-particle physics to better understand the complex many-body ultracold phenomena. The team at NIST and CU Boulder honed in on exploring the limits to universality in a few-body universal phenomenon called Efimov physics.

    Initially theorized in the context of nuclear physics, this exotic quantum phenomenon predicts that strong two-body interactions can mediate three-body attraction and form weakly bound three-body states called Efimov trimers. In fact, there are an infinite number of Efimov trimers, whose sizes and energies all relate to one another by a universal numerical factor.

    In addition to this universal scaling, researchers later noted that in atomic systems, all Efimov trimer sizes are the same (in rescaled units), irrespective of chosen atomic species or of the exact details in the underlying two-body interactions that mediate the three-body forces in Efimov physics. The latter universal aspect of Efimov physics is known as “van der Waals universality,” and was deemed true until the recent study.

    “The importance of universality in Efimov physics is that we are able to understand and predict the full few-body interaction picture up to arbitrary large length scales, given only broad knowledge of the two-body physics,” Chapurin said. “Our measurement shows that this is not always the case, demonstrating the first deviation from van der Waals universality and testing the limits of universal physics in a few-body system.”

    3
    A visualization of Efimov trimers, whose three-body attraction is mediated by the long-ranged two-body forces, represented by the golden color. Despite the complex details and individuality of particular atomic species, represented by different polyhedra at the cores, these trimers have similar shapes and sizes, depicting universality. The hint of a crack in the universal nature, as first observed by the researchers in the study, is depicted by subtle size difference of the trimer in the center. Figure credit: Steven Burrows, JILA.

    Chapurin and colleagues performed precise few-body measurements to determine the properties of Efimov trimers in an ultracold potassium gas. The high degree of control over experimental parameters, along with low statistical and systematic errors, allowed them to find the first compelling evidence of non-universal Efimov trimers. The researchers discovered Efimov trimers with sizes that are significantly larger than what the universal theory predicts.

    “Our measurements, with unprecedented precision, revealed a surprising result: the first definitive deviation from van der Waals universality,” Chapurin said. “We measured Efimov trimer sizes to be different from what universal theory predicts and different from all previous measurements in different atomic species.”

    To better understand their observations, the researchers developed a new three-body theoretical model. Their model suggests that in rare circumstances, the microscopic/fine details in the problem (in this case, the complex spin interactions) can drastically affect macroscopic observables such as the size of the Efimov trimers.

    “We found that a refined three-body model based on our precise measurements of two-body interactions, arguably the most accurate measurement of two-body physics in an ultracold system, can account for the observed nonuniversal result,” Chapurin explained. “In this rare occurrence, the fine and complex microscopic details of interactions crack the universal nature of Efimov physics.”

    Although experimental observations clearly point to a strong deviation from van der Waals universality, “not all that is universal is lost,” according to Jose D’Incao, also a researcher in the study. He added that: “one of the premises of universality still persist: by only knowing how two atoms interact, all low energy properties of Efimov triatomic systems can be derived, without the need to refer to the more traditional and complicated three-body chemical forces.”

    The study carried out by Chapurin and colleagues gathered new fascinating observations that could enhance the current understanding of universality in few-body physics. Although the researchers were able to provide a tentative explanation, many questions remain unanswered.

    For instance, while their paper offers insight for the observed deviation from universality of the first Efimov state, the effect of such complex microscopic physics on the consecutive Efimov states (in the infinite Efimov series) is still an open question. Studies of these weakly bound consecutive states require ever colder temperatures (less than one billionth of a degree above the absolute zero) that are best attained in a microgravity environment. The team, who is part of the larger JILA collaboration, hope to address this question by performing future experiments in the Cold Atom Laboratory on the International Space Station.

    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 10:58 am on September 27, 2018 Permalink | Reply
    Tags: , , , NIST - National Institute of Standards and Technology, Researchers can watch changes happen over time millisecond by millisecond, The instrument offers scientists the ability and even ten times smaller down to one nanometer, VSANS   

    From NIST: “New NIST Instrument Will Give Scientists a Window on Change at the Nanoscale” 


    From NIST

    September 26, 2018

    Chad Boutin
    charles.boutin@nist.gov
    (301) 975-4261

    1
    Introducing the new Very Small Angle Neutron Scattering (VSANS) instrument, which will help scientists at the NIST Center for Neutron Research (NCNR) explore objects at the size scale important for nanotechnology.

    It looks more like a long water main pipe than a microscope, but a new custom-built instrument at the National Institute of Standards and Technology (NIST) will give scientists new ability to glimpse moment-by-moment changes in materials on the crucial nanometer scale.

    The tool’s name is almost as lengthy as its 45-meter footprint—it’s called the Very Small Angle Neutron Scattering (VSANS) instrument. Culminating from several years of in-house engineering, VSANS fills a gap in vision that U.S. researchers have craved for at least a decade: the ability to spot nanometer-scale changes in materials that could improve the medicines in your cabinet, the chips in your computer and even the soap in your shower.

    The scale where “things happen” in those and other materials is right between 10 and 1,000 nanometers—the realm of nanotechnology. A view at this size scale means you can watch how chains of molecules assemble themselves into more complicated structures or observe how a promising new prototype electronic switch changes from one configuration to another. Understanding these changes is key to harnessing them.

    “It’s the most critical length scale for seeing the emergent properties of materials,” said NIST’s Dan Neumann, a physicist at the NIST Center for Neutron Research (NCNR). “You want to know why it works the way it does, so you can improve it.”

    The instrument offers scientists the ability to see at this scale, and even ten times smaller, down to one nanometer. Moreover, researchers can watch changes happen over time, millisecond by millisecond. Other instruments at the NCNR use a similar approach as VSANS for peeking inside solid objects, but they do not provide structural information over such a broad length scale, nor can they reveal dynamic changes.

    Part of the instrument’s appeal is its ability to explore biology. Among the most important targets for drugs is also one of the most difficult to study: membrane proteins. Lodged within the protective outer membrane of our cells, these complicated molecules resist study because they are difficult to crystallize (a strategy useful for analyzing most other proteins), but comprehending their behavior is crucial for drug design.

    “Using neutrons, we can see these proteins as they look in their natural state,” said Kenneth Rubinson, a guest researcher from Wright State University in Ohio who has been performing experiments at the NCNR for 15 years. “We hope VSANS will let us get this data faster so we can get better models of the structure.”

    VSANS also allows its users to explore objects at multiple length scales simultaneously, providing more perspective than either scale alone would offer. For example, one approach for delivering drugs effectively involves encapsulating them in nanometer-sized bubbles called micelles so that they remain in the bloodstream as they travel to their targets. Seeing how these micelles behave and connect with one another appeals to NIST’s Elizabeth Kelley, an instrument scientist at the NCNR.

    “With other instruments, it’s like making a movie where you can only see half the picture at once,” she said. “I’ve lost a lot of time trying to optimize the location we’re looking at so we don’t miss anything, but with VSANS you don’t have that problem. Seeing how these micelles interact over time can help us understand how a drug can get released, or how efficient you are at encapsulating it.”

    Micelles also form in everyday products like shampoo. Tweaking their behavior might make all of us happier once we’re out of the shower.

    “We don’t think about it, but shampoo is actually a complex fluid made of nanoparticles and polymers, and their basic physical properties ultimately affects, for example, how much a shampoo dries out your hair,” said John Riley, who is finishing a National Research Council postdoctoral fellowship at the NCNR. “We’re just looking at the micelles’ basic properties here, but the more you know about those properties, the more you can control what that fluid does.”

    With VSANS, researchers at the NCNR expect many new discoveries in the pipeline.

    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 2:00 pm on December 14, 2017 Permalink | Reply
    Tags: A nanofluidic staircase machined with subnanometer precision by a focused ion beam separates nanoparticles by size, , Atomic Blasting Creates New Devices to Measure Nanoparticles, Center for Nanoscale Science and Technology, , NIST - National Institute of Standards and Technology   

    From NIST: “Atomic Blasting Creates New Devices to Measure Nanoparticles” 


    NIST

    December 14, 2017

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

    1
    A nanofluidic staircase machined with subnanometer precision by a focused ion beam separates nanoparticles by size. The device is also a reference material to accurately measure nanoparticle size and compare it to optical brightness, which could aid in the quality control of consumer products. Credit: NIST

    Like sandblasting at the nanometer scale, focused beams of ions ablate hard materials to form intricate three-dimensional patterns. The beams can create tiny features in the lateral dimensions—length and width, but to create the next generation of nanometer-scale devices, the energetic ions must precisely control the features in the vertical dimension—depth. Now, researchers at the National Institute of Standards and Technology (NIST) have demonstrated that a standard ion-beam technique can be fine-tuned to make structures with depths controlled to within the diameter of a single silicon atom.

    Taking advantage of that newly demonstrated precision, the NIST team used this standard machining technique to fabricate devices that allow precise measurement of the size of nanoparticles in a liquid. The nanofluidic devices, which have the potential for mass production, could become a new laboratory standard for determining nanoparticle size. Such measurements could expedite quality control in industrial applications of nanoparticles.

    “We have tested and advanced what is possible to make and measure below one nanometer,” said NIST researcher Samuel Stavis. He and his colleagues from NIST and the Maryland NanoCenter at the University of Maryland in College Park reported their findings in a recent issue of Lab on a Chip.

    Although engineers have for years used ion beams to fix defects in integrated circuits and machine tiny parts in optical and mechanical systems, those applications did not require the depth control the team has now reported.

    To realize the full potential of the process, the team explored several ways of using a focused beam of gallium ions to mill the surfaces of silicon, silicon nitride and silicon dioxide—materials that are common for the fabrication of nanoscale devices used in electronics, optics and mechanics. The researchers used an atomic force microscope, which features a sensitive probe to measure the depth of the topography formed by the ion beam. Careful measurements were important to testing the limits of the ion-beam technique. The facilities at NIST enabled the team to undertake both tasks—precision fabrication and precision measurement.

    The team applied the new capability to improve the measurement of the size of nanoparticles. Using a gallium ion beam, the researchers machined staircase patterns in silicon dioxide and then enclosed them to control the flow of fluid at the nanoscale. In some devices, the researchers machined a staircase with a step size of 1.1 nanometers; they machined others with a step size of 0.6 nanometers—just a few atoms in depth.

    The steps of the staircase pattern precisely separated nanoparticles immersed in water according to their size. Nanoparticles flowed in to the deepest step at the bottom of the staircase, but only the smaller ones could ascend towards the shallowest step at the top; larger nanoparticles could not fit through and remain trapped at the bottom set of steps. Fluorescent dye within the nanoparticles enabled the team to record their location with an optical microscope and match that location to the known depth of the staircase.

    Comparing the nanoparticle sizes indicated by this method with the sizes measured using electron microscopy revealed a match that was accurate to within one nanometer. This good agreement of the different measurements suggests that the devices can serve not only as a particle separator but as a reference material for measuring the sizes of nanoparticles.

    Manufacturers who routinely perform quality control on nanoparticles—determining not only their average size, but how many of the nanoparticles are slightly smaller or larger than average from batch to batch—could benefit from the new technique. The newly fabricated devices, in combination with an inexpensive optical microscope to pinpoint the locations of nanoparticles, offer a potentially faster and more economical route than other measurement techniques, Stavis noted. The team is now investigating how the devices could serve as master molds for the mass production of inexpensive replicas.

    Because the nanoparticles were measured with an optical microscope, the NIST team could also explore the relationship between the size of nanoparticles and another key property—their brightness. Clarifying that relationship is important for understanding the properties of such nanoparticles as quantum dots for color displays, gold nanoparticles for biomedical sensors, and other nanoparticles for drug delivery.

    The team detailed their process so that researchers at NIST can readily take advantage of and adapt the process for their own work. Several customers of NIST’s nanotechnology user facility, the Center for Nanoscale Science and Technology, where the work was conducted, have expressed interest in adapting the technology for measuring both the size and brightness of nanoparticles in these consumer products.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    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 11:01 am on November 6, 2017 Permalink | Reply
    Tags: An international task force of metrologists has updated the values of four fundamental constants—Planck’s constant (h) the elementary charge (e) Boltzmann’s constant (k); and Avagadro’s number, Nailing Down Four Fundamental Constants, NIST - National Institute of Standards and Technology, , The redefinition of these fundamental constants represents the latest step in a long slow march away from physical “artifact-based” SI standards and toward standards based on exact values of funda   

    From Optics & Photonics: “Nailing Down Four Fundamental Constants” 

    Optics & Photonics

    06 November 2017
    Stewart Wills

    1
    A NIST wallet card displays the fundamental constants and physical values that will define the revised system of SI units. [Image: Stoughton/NIST]

    An international task force of metrologists has updated the values of four fundamental constants—Planck’s constant (h), the elementary charge (e), Boltzmann’s constant (k); and Avagadro’s number, NA (Metrologia, doi: 10.1088/1681-7575/aa950a).

    The new values for these constants, which rest on an analysis of state-of-the-art measurements from a worldwide assemblage of metrology labs, won’t, alas, change the morning reading on your bathroom scale. But they’re a big deal for metrologists, as they set up a comprehensive reassessment of the International System of Units (SI), or metric system, slated for November 2018—when the metrology community is expected to redefine all seven basic SI units solely in terms of fundamental constants and invariant properties of atoms.

    Moving away from physical artifacts

    The redefinition of these fundamental constants represents the latest step in a long, slow march away from physical, “artifact-based” SI standards and toward standards based on exact values of fundamental constant. Perhaps the most celebrated physical standard was the platinum-iridium bar located in Paris that, for decades, denoted the precise dimensions of the basic SI unit of length, the meter.

    After a long process—during which the scientific community tried, and failed, to replace the bar with a universally accepted standard based a wavelength of light—the metrology community eventually simply turned the problem around. Metrologists defined a fundamental constant, the speed of light in vacuum (c), as an exact value (299,792,458 m/s) and used that fundamental constant to define the exact length of a meter. (For more on the standard-meter story, see “Mercury-198 and the Standard Meter,” OPN, September 2017.)

    Dethroning “Le Grand K”

    Metrologists would like to achieve a similar fundamental-constant-based standard for all seven basic SI units: the meter, the second, the mole, the ampere, the kelvin, the candela, and the kilogram. This would enable researchers worldwide to make authoritative measurements using precisely the same standard units anywhere on the planet, and on any scale of measurement.

    The kilogram constitutes a particular thorn in the metrology community’s side; it is the last remaining SI unit that still is defined by a physical artifact—“Le Grand K,” a platinum-iridium cylinder stored in France that has represented the standard kilogram since 1879. In principle, that means that local standards for the kilogram elsewhere in the world must be calibrated directly against that physical original.

    In other cases, standard SI units have been defined by theoretical ideals difficult to realize in practice. For example, temperature has been defined in terms of the triple point of pure water in a sealed glass cell—begging the question of how to make the water sufficiently pure, and of potential measurement inaccuracies as one gets farther and farther from the triple point.

    Hammering down uncertainties

    In principle, defining the SI measurements in terms of the exact value of fundamental constants avoids these local and practical difficulties—but it requires a highly precise, international consensus definition of the values of the constants themselves. The work of creating those consensus values for h, e, k, and NA falls to the Task Group on Fundamental Constants of the international Committee on Data for Science and Technology (CODATA), which periodically reviews fundamental-constant values based on the best available experimental evidence. The team proceeded by collecting measurements from multiple techniques and labs, and using a number of techniques to harmonize the data and minimize uncertainties.

    For the redefinition of Planck’s constant and Avogadro’s number, for example, the CODATA task group relied on a suite of measurements using a so-called Kibble balance and X-ray crystal-density measurements of a specific sphere of ultrapure silicon-28. As a result, the task group was able to hammer down uncertainties in these constants to just four parts per billion.

    Relevant to precise measurements

    The four new constant definitions join three other constants—the speed of light, the hyperfine transition frequency of cesium (ΔνCs), and the luminous efficacy constant (Kcd)—that have previously been exactly defined, and have been used to provide definitions of units such as the meter, the second and the candela. The new definition of Planck’s constant, which has units of kg-m2/s, will be used to provide a worldwide, invariant definition of the kilogram, replacing “Le Grand K”; the new standard Boltzmann’s constant will underlie a constant-based definition of the kelvin temperature unit, superseding the definition based on the triple point of water.

    The task group members stress that the changes to these constants will have little relevance day to day, in the lab or elsewhere. “The whole thing,” said Peter Mohr, a member of the task group who works at the U.S. National Institute of Standards and Technology, “is geared to not have any impact on the average person.” Yet it the shift will have considerable relevance to contemporary metrology researchers, whose work increasingly involves measurements at precisions undreamed of in earlier eras.

    For this reason, according to CODATA, while the shift to the full suite of SI units based on the new values of these fundamental constants will be decided in November 2018, its official rollout won’t come until 20 May 2019—“World Metrology Day”—to give the community time to adapt.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Optics & Photonics News (OPN) is The Optical Society’s monthly news magazine. It provides in-depth coverage of recent developments in the field of optics and offers busy professionals the tools they need to succeed in the optics industry, as well as informative pieces on a variety of topics such as science and society, education, technology and business. OPN strives to make the various facets of this diverse field accessible to researchers, engineers, businesspeople and students. Contributors include scientists and journalists who specialize in the field of optics. We welcome your submissions.

     
  • richardmitnick 8:13 am on October 23, 2017 Permalink | Reply
    Tags: Antennas, , “Specific radiation efficiency”, , , Nanotube fiber antennas as capable as copper, NIST - National Institute of Standards and Technology,   

    From Rice: “Nanotube fiber antennas as capable as copper” 

    Rice U bloc

    Rice University

    October 23, 2017
    Mike Williams

    1
    Rice University graduate student Amram Bengio sets up a nanotube fiber antenna for testing. Scientists at Rice and the National Institute of Standards and Technology have determined that nanotube fibers made at Rice can be as good as copper antennas but 20 times lighter. Photo by Jeff Fitlow

    Rice researchers show their flexible fibers work well but weigh much less

    Fibers made of carbon nanotubes configured as wireless antennas can be as good as copper antennas but 20 times lighter, according to Rice University researchers. The antennas may offer practical advantages for aerospace applications and wearable electronics where weight and flexibility are factors.

    The research appears in Applied Physics Letters.

    The discovery offers more potential applications for the strong, lightweight nanotube fibers developed by the Rice lab of chemist and chemical engineer Matteo Pasquali. The lab introduced the first practical method for making high-conductivity carbon nanotube fibers in 2013 and has since tested them for use as brain implants and in heart surgeries, among other applications.

    The research could help engineers who seek to streamline materials for airplanes and spacecraft where weight equals cost. Increased interest in wearables like wrist-worn health monitors and clothing with embedded electronics could benefit from strong, flexible and conductive fiber antennas that send and receive signals, Pasquali said.

    The Rice team and colleagues at the National Institute of Standards and Technology (NIST) developed a metric they called “specific radiation efficiency” to judge how well nanotube fibers radiated signals at the common wireless communication frequencies of 1 and 2.4 gigahertz and compared their results with standard copper antennas. They made thread comprising from eight to 128 fibers that are about as thin as a human hair and cut to the same length to test on a custom rig that made straightforward comparisons with copper practical.

    “Antennas typically have a specific shape, and you have to design them very carefully,” said Rice graduate student Amram Bengio, the paper’s lead author. “Once they’re in that shape, you want them to stay that way. So one of the first experimental challenges was getting our flexible material to stay put.”

    2
    Bengio prepares a sample nanotube fiber antenna for evaluation. The fibers had to be isolated in Styrofoam mounts to assure accurate comparisons with each other and with copper. Photo by Jeff Fitlow

    Contrary to earlier results by other labs (which used different carbon nanotube fiber sources), the Rice researchers found the fiber antennas matched copper for radiation efficiency at the same frequencies and diameters. Their results support theories that predicted the performance of nanotube antennas would scale with the density and conductivity of the fiber.

    “Not only did we find that we got the same performance as copper for the same diameter and cross-sectional area, but once we took the weight into account, we found we’re basically doing this for 1/20th the weight of copper wire,” Bengio said.

    “Applications for this material are a big selling point, but from a scientific perspective, at these frequencies carbon nanotube macro-materials behave like a typical conductor,” he said. Even fibers considered “moderately conductive” showed superior performance, he said.

    Although manufacturers could simply use thinner copper wires instead of the 30-gauge wires they currently use, those wires would be very fragile and difficult to handle, Pasquali said.

    “Amram showed that if you do three things right — make the right fibers, fabricate the antenna correctly and design the antenna according to telecommunication protocols — then you get antennas that work fine,” he said. “As you go to very thin antennas at high frequencies, you get less of a disadvantage compared with copper because copper becomes difficult to handle at thin gauges, whereas nanotubes, with their textile-like behavior, hold up pretty well.”

    Co-authors of the paper are, from Rice, graduate students Lauren Taylor and Peiyu Chen, alumnus Dmitri Tsentalovich and Aydin Babakhani, an associate professor of electrical and computer engineering, and, from NIST in Boulder, Colo., postdoctoral researcher Damir Senic, research engineer Christopher Holloway, physicist Christian Long, research scientists David Novotny and James Booth and physicist Nathan Orloff. Pasquali is a professor of chemical and biomolecular engineering, of materials science and nanoengineering and of chemistry.

    The U.S. Air Force supported the research.

    See the full article here .

    Please help promote STEM in your local schools.

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    Rice U campus

    In his 1912 inaugural address, Rice University president Edgar Odell Lovett set forth an ambitious vision for a great research university in Houston, Texas; one dedicated to excellence across the range of human endeavor. With this bold beginning in mind, and with Rice’s centennial approaching, it is time to ask again what we aspire to in a dynamic and shrinking world in which education and the production of knowledge will play an even greater role. What shall our vision be for Rice as we prepare for its second century, and how ought we to advance over the next decade?

    This was the fundamental question posed in the Call to Conversation, a document released to the Rice community in summer 2005. The Call to Conversation asked us to reexamine many aspects of our enterprise, from our fundamental mission and aspirations to the manner in which we define and achieve excellence. It identified the pressures of a constantly changing and increasingly competitive landscape; it asked us to assess honestly Rice’s comparative strengths and weaknesses; and it called on us to define strategic priorities for the future, an effort that will be a focus of the next phase of this process.

     
  • richardmitnick 9:10 pm on October 7, 2017 Permalink | Reply
    Tags: (3-D) quantum gas atomic clock, , , JILA physicists have created an entirely new design for an atomic clock, , NIST - National Institute of Standards and Technology, , Quantum gas,   

    From NIST: “JILA’s 3-D Quantum Gas Atomic Clock Offers New Dimensions in Measurement” 


    NIST

    October 05, 2017

    Laura Ost
    laura.ost@nist.gov
    (303) 497-4880

    1
    JILA

    4
    CU Boulder

    1
    JILA’s three-dimensional (3-D) quantum gas atomic clock consists of a grid of light formed by three pairs of laser beams. A stack of two tables is used to configure optical components around a vacuum chamber. Shown here is the upper table, where lenses and other optics are mounted. A blue laser beam excites a cube-shaped cloud of strontium atoms located behind the round window in the middle of the table. Strontium atoms fluorescence strongly when excited with blue light. Credit: G.E. Marti/JILA

    JILA physicists have created an entirely new design for an atomic clock, in which strontium atoms are packed into a tiny three-dimensional (3-D) cube at 1,000 times the density of previous one-dimensional (1-D) clocks. In doing so, they are the first to harness the ultra-controlled behavior of a so-called “quantum gas” to make a practical measurement device.

    With so many atoms completely immobilized in place, JILA’s cubic quantum gas clock sets a record for a value called “quality factor” and the resulting measurement precision. A large quality factor translates into a high level of synchronization between the atoms and the lasers used to probe them, and makes the clock’s “ticks” pure and stable for an unusually long time, thus achieving higher precision.

    Until now, each of the thousands of “ticking” atoms in advanced clocks behave and are measured largely independently. In contrast, the new cubic quantum gas clock uses a globally interacting collection of atoms to constrain collisions and improve measurements. The new approach promises to usher in an era of dramatically improved measurements and technologies across many areas based on controlled quantum systems.

    The new clock is described in the Oct. 6 issue of Science.

    “We are entering a really exciting time when we can quantum engineer a state of matter for a particular measurement purpose,” said physicist Jun Ye of the National Institute of Standards and Technology (NIST). Ye works at JILA, which is jointly operated by NIST and the University of Colorado Boulder.

    The clock’s centerpiece is an unusual state of matter called a degenerate Fermi gas (a quantum gas for Fermi particles), first created in 1999 by Ye’s late colleague Deborah Jin. All prior atomic clocks have used thermal gases. The use of a quantum gas enables all of the atoms’ properties to be quantized, or restricted to specific values, for the first time.

    “The most important potential of the 3-D quantum gas clock is the ability to scale up the atom numbers, which will lead to a huge gain in stability,” Ye said. “Also, we could reach the ideal condition of running the clock with its full coherence time, which refers to how long a series of ticks can remain stable. The ability to scale up both the atom number and coherence time will make this new-generation clock qualitatively different from the previous generation.”

    Until now, atomic clocks have treated each atom as a separate quantum particle, and interactions among the atoms posed measurement problems. But an engineered and controlled collection, a “quantum many-body system,” arranges all its atoms in a particular pattern, or correlation, to create the lowest overall energy state. The atoms then avoid each other, regardless of how many atoms are added to the clock. The gas of atoms effectively turns itself into an insulator, which blocks interactions between constituents.

    The result is an atomic clock that can outperform all predecessors. For example, stability can be thought of as how precisely the duration of each tick matches every other tick, which is directly linked to the clock’s measurement precision. Compared with Ye’s previous 1-D clocks, the new 3-D quantum gas clock can reach the same level of precision more than 20 times faster due to the large number of atoms and longer coherence times.

    The experimental data show the 3-D quantum gas clock achieved a precision of just 3.5 parts error in 10 quintillion (1 followed by 19 zeros) in about 2 hours, making it the first atomic clock to ever reach that threshold (19 zeros). “This represents a significant improvement over any previous demonstrations,” Ye said.

    The older, 1-D version of the JILA clock was, until now, the world’s most precise clock. This clock holds strontium atoms in a linear array of pancake-shaped traps formed by laser beams, called an optical lattice. The new 3-D quantum gas clock uses additional lasers to trap atoms along three axes so that the atoms are held in a cubic arrangement. This clock can maintain stable ticks for nearly 10 seconds with 10,000 strontium atoms trapped at a density above 10 trillion atoms per cubic centimeter. In the future, the clock may be able to probe millions of atoms for more than 100 seconds at a time.

    Optical lattice clocks, despite their high levels of performance in 1-D, have to deal with a tradeoff. Clock stability could be improved further by increasing the number of atoms, but a higher density of atoms also encourages collisions, shifting the frequencies at which the atoms tick and reducing clock accuracy. Coherence times are also limited by collisions. This is where the benefits of the many-body correlation can help.

    The 3-D lattice design—imagine a large egg carton—eliminates that tradeoff by holding the atoms in place. The atoms are fermions, a class of particles that cannot be in the same quantum state and location at once. For a Fermi quantum gas under this clock’s operating conditions, quantum mechanics favors a configuration where each individual lattice site is occupied by only one atom, which prevents the frequency shifts induced by atomic interactions in the 1-D version of the clock.

    JILA researchers used an ultra-stable laser to achieve a record level of synchronization between the atoms and lasers, reaching a record-high quality factor of 5.2 quadrillion (5.2 followed by 15 zeros). Quality factor refers to how long an oscillation or waveform can persist without dissipating. The researchers found that atom collisions were reduced such that their contribution to frequency shifts in the clock was much less than in previous experiments.

    “This new strontium clock using a quantum gas is an early and astounding success in the practical application of the ‘new quantum revolution,’ sometimes called ‘quantum 2.0’,” said Thomas O’Brian, chief of the NIST Quantum Physics Division and Ye’s supervisor. “This approach holds enormous promise for NIST and JILA to harness quantum correlations for a broad range of measurements and new technologies, far beyond timing.”

    Depending on measurement goals and applications, JILA researchers can optimize the clock’s parameters such as operational temperature (10 to 50 nanokelvins), atom number (10,000 to 100,000), and physical size of the cube (20 to 60 micrometers, or millionths of a meter).

    Atomic clocks have long been advancing the frontier of measurement science, not only in timekeeping and navigation but also in definitions of other measurement units and other areas of research such as in tabletop searches for the missing “dark matter” in the universe.

    The National Bureau of Standards, now NIST, invented the first atomic clock in 1948.

    3
    Dr. Harold Lyons (right), inventor of the ammonia absorption cell atomic clock, observes, while Dr. Edward U. Condon, the director of the National Bureau of Standards, examines a model of the ammonia molecule (1949).

    The work is supported by NIST, the Defense Advanced Research Projects Agency and the National Science Foundation.

    See the full article here.

    Please help promote STEM in your local schools.

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    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 4:40 pm on June 7, 2017 Permalink | Reply
    Tags: , , MEMS technologies, MEMS-based three-axis accelerometers, NIST - National Institute of Standards and Technology   

    From NIST: “Intrinsic Properties: The Secret Lives of Accelerometers” 

    NIST

    May 30, 2017

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

    Technical Contact
    Michael Gaitan
    michael.gaitan@nist.gov
    (301) 975-2070

    Accelerometers — devices that measure change in velocity — are built into automobiles, airplanes, cell phones, pacemakers, and scores of other products. They warn of potentially destructive vibration in industrial equipment, buildings, and bridges; register seismic shocks; and guide missiles to their targets.

    Increasingly, they are miniaturized using microelectromechanical systems (MEMS) technologies with component dimensions on the order of micrometers, and simultaneously register acceleration in all three axes of three-dimensional space. Because errors are additive when calculating velocity from acceleration, even minor errors in output can have very serious consequences.

    Yet when three-axis sensitivities and cross-axis sensitivities of a digital three-axis* device are tested at different calibration laboratories, the measurements can vary substantially depending on factors that can be difficult to determine, but often arise from errors with alignment of the test equipment, the internal alignment of the accelerometers in the device, or both.

    Now NIST scientists have devised a methodology designed to reduce or eliminate those differences by characterizing intrinsic properties of an accelerometer – those that are unique to it irrespective of the way it is mounted or tested — thus making possible accurate interlaboratory comparisons.

    “Determination of intrinsic properties is part of NIST’s larger effort to help industry develop standard testing protocols for the new MEMS-based device technologies, which do not exist at present,” says Michael Gaitan of NIST’s Physical Measurement Laboratory, which is working in partnership with the MEMS and Sensors Industry Group (MSIG) and the Institute of Electrical and Electronics Engineers. “Testing was reported by MSIG to be as much as half the cost of manufacturing for these sorts of devices. Manufacturers can’t reduce the cost of physical fabrication very much. But they can find savings in the way they package, test, and calibrate the devices.”

    When MEMS-based, three-axis accelerometers are tested, they are typically mounted on a gimbal system and rotated about three axes — x, y, and z — with measurements taken in different orientations. The measurements are formatted in a three-by-three grid, called a “cross-sensitivity matrix,” used by manufacturers to evaluate device performance. It specifies the relation between the acceleration response along the gimbal axes to the response along the axes of the device under test (DUT).

    2
    MEMS-based, three-axis accelerometers. http://wikid.io.tudelft.nl/WikID/index.php/MEMS-based_accelerometers

    That process, however, assumes that the DUT’s three axes are perfectly orthogonal – at right angles to each other – and that the device has been mounted in perfect alignment with the gimbal axes, which are themselves perfectly aligned. And in the case of testing accelerometer packages after they have been integrated into products, such as smart phones, it assumes that the package was installed in exact alignment with the axes of the phone case. But none of those conditions is guaranteed, and slight deviations in any of the variables can explain why measurements of the same test unit made at different laboratories produce different values.

    “So instead of using the cross-sensitivity matrix alone,” Gaitan says, “we’re defining the device as having intrinsic properties in which the axes of the device are not assumed to be completely orthogonal. There might be some variation in their alignment.”

    In NIST’s measurement protocol, the DUT is mounted on the position and rate table which very accurately rotates the device in specific gradations through 360 degrees on each of the gimbal’s three axes while measuring the device response at each interval. The protocol reveals the DUT’s internal axis alignment, the magnitude of response of each axis in different orientations, and its “signal offset” – the constant amount by which measured readings differ from the “true” value.

    With that information, a central standards laboratory such as NIST could fully characterize the intrinsic properties of one or more DUTs and distribute the devices to other labs, which would use them to compare results and determine, for example, whether readings were skewed because of instrument-related measurement errors.

    Earlier this year, NIST acquired a new position and rate table large enough to permit measurements on entire products that have accelerometers installed. “Our initial gimbal system was a smaller instrument that was useful for making static measurements,” Gaitan says.

    “But now we can make dynamic measurements on objects as large as a cell phone. We can set it to steady-state rotation like a record player, and we can accelerate the rotation rate. That will enable us to make measurements above the 1g acceleration of gravity and measure acceleration by rotation.”

    • Although it is called a “three-axis accelerometer,” the device in fact contains three separate accelerometers, each of which measures velocity change along one axis. Those signals are merged to register movement in three dimensions.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    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 4:06 pm on May 30, 2017 Permalink | Reply
    Tags: Berry phase, Mysterious quantum behavior, NIST - National Institute of Standards and Technology, Quantum properties, Researchers Develop Magnetic Switch to Turn On and Off a Strange Quantum Property   

    From NIST: “Researchers Develop Magnetic Switch to Turn On and Off a Strange Quantum Property” 

    NIST

    May 25, 2017

    Jennifer Huergo
    jennifer.huergo@nist.gov
    (301) 975-6343

    1
    These images show the orbital paths of electrons trapped within a circular region within graphene. In the classical orbit (top image), an electron that travels in a complete circuit has the same physical state as when it started on the path. However, when an applied magnetic field reaches a critical value, (bottom image), an electron completing a circuit has a different physical state its original one. The change is called a Berry phase, and the magnetic field acts as a switch to turn the Berry phase on. The result is that the electron is raised to a higher energy level. Credit: Christopher Gutiérrez, Daniel Walkup/NIST

    When a ballerina pirouettes, twirling a full revolution, she looks just as she did when she started. But for electrons and other subatomic particles, which follow the rules of quantum theory, that’s not necessarily so. When an electron moves around a closed path, ending up where it began, its physical state may or may not be the same as when it left.

    Now, there is a way to control the outcome, thanks to an international research group led by scientists at the National Institute of Standards and Technology (NIST). The team has developed the first switch that turns on and off this mysterious quantum behavior. The discovery promises to provide new insight into the fundamentals of quantum theory and may lead to new quantum electronic devices.

    To study this quantum property, NIST physicist and fellow Joseph A. Stroscio and his colleagues studied electrons corralled in special orbits within a nanometer-sized region of graphene—an ultrastrong, single layer of tightly packed carbon atoms. The corralled electrons orbit the center of the graphene sample just as electrons orbit the center of an atom. The orbiting electrons ordinarily retain the same exact physical properties after traveling a complete circuit in the graphene. But when an applied magnetic field reaches a critical value, it acts as a switch, altering the shape of the orbits and causing the electrons to possess different physical properties after completing a full circuit.

    The researchers report their findings in the May 26, 2017 issue of Science.

    The newly developed quantum switch relies on a geometric property called the Berry phase, named after English physicist Sir Michael Berry who developed the theory of this quantum phenomenon in 1983. The Berry phase is associated with the wave function of a particle, which in quantum theory describes a particle’s physical state. The wave function—think of an ocean wave—has both an amplitude (the height of the wave) and a phase—the location of a peak or trough relative to the start of the wave cycle.

    When an electron makes a complete circuit around a closed loop so that it returns to its initial location, the phase of its wave function may shift instead of returning to its original value. This phase shift, the Berry phase, is a kind of memory of a quantum system’s travel and does not depend on time, only on the geometry of the system—the shape of the path. Moreover, the shift has observable consequences in a wide range of quantum systems.

    Although the Berry phase is a purely quantum phenomenon, it has an analog in non-quantum systems. Consider the motion of a Foucault pendulum, which was used to demonstrate Earth’s rotation in the 19th century. The suspended pendulum simply swings back and forth in the same vertical plane, but appears to slowly rotate during each swing—a kind of phase shift—due to the rotation of Earth beneath it.

    Since the mid-1980s, experiments have shown that several types of quantum systems have a Berry phase associated with them. But until the current study, no one had constructed a switch that could turn the Berry phase on and off at will. The switch developed by the team, controlled by a tiny change in an applied magnetic field, gives electrons a sudden and large increase in energy.

    Several members of the current research team—based at the Massachusetts Institute of Technology and Harvard University—developed the theory for the Berry phase switch.

    To study the Berry phase and create the switch, NIST team member Fereshte Ghahari built a high-quality graphene device to study the energy levels and the Berry phase of electrons corralled within the graphene.

    First, the team confined the electrons to occupy certain orbits and energy levels. To keep the electrons penned in, team member Daniel Walkup created a quantum version of an electric fence by using ionized impurities in the insulating layer beneath the graphene. This enabled a scanning tunneling microscope at NIST’s nanotechnology user facility, the Center for Nanoscale Science and Technology, to probe the quantum energy levels and Berry phase of the confined electrons.

    The team then applied a weak magnetic field directed into the graphene sheet. For electrons moving in the clockwise direction, the magnetic field created tighter, more compact orbits. But for electrons moving in counterclockwise orbits, the magnetic field had the opposite effect, pulling the electrons into wider orbits. At a critical magnetic field strength, the field acted as a Berry phase switch. It twisted the counterclockwise orbits of the electrons, causing the charged particles to execute clockwise pirouettes near the boundary of the electric fence.

    Ordinarily, these pirouettes would have little consequence. However, said team member Christopher Gutiérrez, “the electrons in graphene possess a special Berry phase, which switches on when these magnetically induced pirouettes are triggered.”

    When the Berry phase is switched on, orbiting electrons abruptly jump to a higher energy level. The quantum switch provides a rich scientific tool box that will help scientists exploit ideas for new quantum devices, which have no analog in conventional semiconductor systems, said Stroscio.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    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 8:43 pm on May 21, 2017 Permalink | Reply
    Tags: , , , , , , NanoFab, NIST - National Institute of Standards and Technology,   

    From NIST: “Nanocollaboration Leads to Big Things” 

    NIST

    May 12, 2017 [Nothing like being timely getting into social media.]

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

    1
    Entrance to NIST’s Advanced Measurement Laboratory in Gaithersburg, Maryland. Credit: Photo Courtesy HDR Architecture, Inc./Steve Hall Copyright Hedrich Blessing

    Roche Sequencing Solutions engineer Juraj Topolancik was looking for a way to decode DNA from cancer patients in a matter of minutes.

    Rajesh Krishnamurthy, a researcher with the startup company 3i Diagnostics, needed help in fabricating a key component of a device that rapidly identifies infection-causing bacteria.

    Ranbir Singh, an engineer with GeneSiC Semiconductor Inc., in Dulles, Virginia, sought to construct and analyze a semiconductor chip that transmits voltages large enough to power electric cars and spacecraft.

    These researchers all credit the NanoFab, located at the Center for Nanoscale Science and Technology (CNST) on the Gaithersburg, Maryland campus of the National Institute of Standards and Technology (NIST). The NanoFab provides cutting-edge nanotechnology capabilities for NIST scientists that is also accessible to outside users, with supplying the state-of-art tools, know-how and dependability to realize their goals.


    Learn more about the CNST NanoFab, where scientists from government, academia and industry can use commercial, state-of-the-art tools at economical rates, and get help from dedicated, full-time technical support staff. Voices: David Baldwin (Great Ball of Light, Inc.), Elisa Williams (Scientific & Biomedical Microsystems), George Coles (Johns Hopkins Applied Physics Laboratory) and William Osborn (NIST).

    When Krishnamurthy, whose company is based in Germantown, Maryland, needed an infrared filter for the bacteria-identifying chip, proximity was but one factor in reaching out to the NanoFab.

    “Even more important was the level of expertise you have here,” he says. “The attention to detail and the trust we have in the staff is so important—we didn’t have to worry if they would do a good job, which gives us tremendous peace of mind,” Krishnamurthy notes.

    The NanoFab also aided his project in another, unexpected way. Krishnamurthy had initially thought that the design for his company’s device would require a costly, highly customized silicon chip. But in reviewing design plans with engineers at the NanoFab, “they came up with a very creative way” to use a more standard, less expensive silicon wafer that would achieve the same goals, he notes.

    “The impact in the short term is that we didn’t have to pay as much [to build and test] the device at the NanoFab, which matters quite a bit because we’re a start-up company,” says Krishnamurthy. “In the long run, this will be a huge factor in [enabling us to mass produce] the device, keeping our costs low because, thanks to the input from the NanoFab, the source material is not a custom material.”

    Singh came to the NanoFab with a different mission. His company is developing a gallium nitride semiconductor device durable enough to transmit hundreds to thousands of volts without deteriorating. He relies on the NanoFab’s metal deposition tools and high-resolution lithography instruments to finish building and assess the properties of the device.

    2
    Semiconductor device, fabricated with the help of the NanoFab, designed to transmit high voltages.
    Credit: GeneSiC Semiconductor Inc.

    “Not only is there a wide diversity of tools, but within each task there are multiple technologies,” Singh adds.

    For instance, he notes, technologies offered at the NanoFab for depositing exquisitely thin and highly uniform layers of metal—which Singh found crucial for making reliable electrical contacts—include both evaporation and sputtering, he says.

    The wide range of metals available for deposition at the NanoFab, uncommon at other nanotech facilities, was another draw.

    “We needed different metals compared to those commonly used on silicon wafers and the NanoFab provided those materials,” notes Singh.

    Topolancik, the Roche Sequencing Solutions engineer, needed high precision etching and deposition tools to fabricate a device that may ultimately improve cancer treatment. His company‘s plan to rapidly sequence DNA from cancer patients could quickly determine if potential anti-cancer drugs and those already in use are producing the genetic mutations necessary to fight cancer.

    “We want to know if the drug is working, and if not, to stop using it and change the treatment,” says Topolancik.

    In the standard method to sequence the double-stranded DNA molecule, a strand is peeled off and resynthesized, base by base, with each base—cytosine, adenine, guanine and thymine—tagged with a different fluorescent label.

    “It’s a very accurate but slow method,” says Topolancik.

    Instead of peeling apart the molecule, Topolancik is devising a method to read DNA directly, a much faster process. Borrowing a technique from the magnetic recording industry, he sandwiches the DNA between two electrodes separated by a gap just nanometers in width.

    3

    Illustration of experiment to directly identify the base pairs of a DNA strand (denoted by A, C, T, G in graph). Tunneling current flows through DNA placed between two closely spaced electrodes. Different bases allow different amounts of current to flow, revealing the components of the DNA molecule.
    Credit: J. Topolancik/Roche Sequencing Solutions

    According to quantum theory, if the gap is small enough, electrons will spontaneously “tunnel” from one electrode to the other. In Topolancik’s setup, the tunneling electrons must pass through the DNA in order to reach the other electrode.

    The strength of the tunneling current identifies the bases of the DNA trapped between the electrodes. It’s an extremely rapid process, but for the technique to work reliably, the electrodes and the gap between them must be fabricated with extraordinarily high precision.

    That’s where the NanoFab comes in. To deposit layers of different metals just nanometers in thickness on a wafer, Topolancik relies on the NanoFab’s ion beam deposition tool. And to etch a pattern in those ultrathin, supersmooth layers without disturbing them—a final step in fabricating the electrodes—requires the NanoFab’s ion etching instrument.

    “These are specialty tools that are not usually accessible in academic facilities, but here [at the NanoFab] you have full, 24/7 access to them,” says Topolancik. “And if a tool goes down, it gets fixed right away,” he adds. “People here care about you, they want you to succeed because that’s the mission of the NanoFab.” As a result, he notes, “I can get done here in two weeks what would take half a year any place else.”


    Take a 360-degree walking tour of the CNST NanoFab in this video!

    See the full article here.

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    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.
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