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  • 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.

    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 11:59 am on August 14, 2019 Permalink | Reply
    Tags: , , , NIST, Particle number concentrations   

    From NIST: “Solving the Big Problem of Measuring Tiny Nanoparticles” 


    From NIST

    August 14, 2019

    Alison Gillespie
    alison.gillespie@nist.gov
    (301) 975-2316

    1
    Scientists have long debated the most effective way to measure nanoparticles so that results can be shared across labs. NIST researchers have found that one approach — particle number concentrations — may be better than others for most applications. Credit: N. Hanacek/NIST

    Tiny nanoparticles play a gargantuan role in modern life, even if most consumers are unaware of their presence. They provide essential ingredients in sunscreen lotions, prevent athlete’s foot fungus in socks, and fight microbes on bandages. They enhance the colors of popular candies and keep the powdered sugar on doughnuts powdery. They are even used in advanced drugs that target specific types of cells in cancer treatments.

    When chemists analyze a sample, however, it is challenging to measure the sizes and quantities of these particles — which are often 100,000 times smaller than the thickness of a piece of paper. Technology offers many options for assessing nanoparticles, but experts have not reached a consensus on which technique is best.

    In a new paper from the National Institute of Standards and Technology (NIST) and collaborating institutions, researchers have concluded that measuring the range of sizes in nanoparticles — instead of just the average particle size — is optimal for most applications.

    “It seems like a simple choice,” said NIST’s Elijah Petersen, the lead author of the paper, which was published today in Environmental Science: Nano. “But it can have a big impact on the outcome of your assessment.”

    As with many measurement questions, precision is key. Exposure to a certain amount of some nanoparticles could have adverse effects. Pharmaceutical researchers often need exactitude to maximize a drug’s efficacy. And environmental scientists need to know, for example, how many nanoparticles of gold, silver or titanium could potentially cause a risk to organisms in soil or water.

    Using more nanoparticles than needed in a product because of inconsistent measurements could also waste money for manufacturers.

    Although they might sound ultramodern, nanoparticles are neither new nor based solely on high-tech manufacturing processes. A nanoparticle is really just a submicroscopic particle that measures less than 100 nanometers on at least one of its dimensions. It would be possible to place hundreds of thousands of them onto the head of a pin. They are exciting to researchers because many materials act differently at the nanometer scale than they do at larger scales, and nanoparticles can be made to do lots of useful things.

    Nanoparticles have been in use since the days of ancient Mesopotamia, when ceramic artists used extremely small bits of metal to decorate vases and other vessels. In fourth-century Rome, glass artisans ground metal into tiny particles to change the color of their wares under different lighting. These techniques were forgotten for a while but rediscovered in the 1600s by resourceful manufacturers for glassmaking again. Then, in the 1850s, scientist Michael Faraday extensively researched ways to use various kinds of wash mixes to change the performance of gold particles.

    Modern nanoparticle research advanced quickly in the mid-20th century due to technological innovations in optics. Being able to see the individual particles and study their behavior expanded the possibilities for experimentation. The largest advances came, however, after experimental nanotechnology took off in the 1990s. Suddenly, the behavior of single particles of gold and many other substances could be closely examined and manipulated. Discoveries about the ways that small amounts of a substance would reflect light, absorb light, or change in behavior were numerous, leading to the incorporation of nanoparticles into many more products.

    Debates have since followed about their measurement. When assessing the response of cells or organisms to nanoparticles, some researchers prefer measuring particle number concentrations (sometimes called PNCs by scientists). Many find PNCs challenging since extra formulas must be employed when determining the final measurement. Others prefer measuring mass or surface area concentrations.

    PNCs are often used for characterizing metals in chemistry. The situation for nanoparticles is inherently more complex, however, than it is for dissolved organic or inorganic substances because unlike dissolved chemicals, nanoparticles can come in a wide variety of sizes and sometimes stick together when added to testing materials.

    “If you have a dissolved chemical, it’s always going to have the same molecular formula, by definition,” Petersen says. “Nanoparticles don’t just have a certain number of atoms, however. Some will be 9 nanometers, some will be 11, some might be 18, and some might be 3.”

    The problem is that each of those particles may be fulfilling an important role. While a simple estimate of particle number is perfectly fine for some industrial applications, therapeutic applications require much more robust measurement. In the case of cancer therapies, for example, each particle, no matter how big or small, may be delivering a needed antidote. And just as with any other kind of dosage, nanoparticle dosage must be exact in order to be safe and effective.

    Using the range of particle sizes to calculate the PNC will often be the most helpful in most cases, said Petersen. The size distribution doesn’t use a mean or an average but notes the complete distribution of sizes of particles so that formulas can be used to effectively discover how many particles are in a sample.

    But no matter which approach is used, researchers need to make note of it in their papers, for the sake of comparability with other studies. “Don’t assume that different approaches will give you the same result,” he said.

    Petersen adds that he and his colleagues were surprised by how much the coatings on nanoparticles could impact measurement. Some coatings, he noted, can have a positive electrical charge, causing clumping.

    Petersen worked in collaboration with researchers from federal laboratories in Switzerland, and with scientists from 3M who have previously made many nanoparticle measurements for use in industrial settings. Researchers from Switzerland, like those in much of the rest of Europe, are keen to learn more about measuring nanoparticles because PNCs are required in many regulatory situations. There hasn’t been much information on which techniques are best or more likely to yield the most precise results across many applications.

    “Until now we didn’t even know if we could find agreement among labs about particle number concentrations,” Petersen says. “They are complex. But now we are beginning to see it can be done.”

    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 3:32 pm on May 2, 2019 Permalink | Reply
    Tags: "Sculpting Super-Fast Light Pulses: NIST Nanopillars Shape Light Precisely for Practical Applications", , Essential for sending information through high-speed optical circuits and in probing atoms and molecules that vibrate thousands of trillions of times a second, NIST,   

    From NIST: “Sculpting Super-Fast Light Pulses: NIST Nanopillars Shape Light Precisely for Practical Applications” 


    From NIST

    May 02, 2019

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

    Imagine being able to shape a pulse of light in any conceivable manner—compressing it, stretching it, splitting it in two, changing its intensity or altering the direction of its electric field.

    Controlling the properties of ultrafast light pulses is essential for sending information through high-speed optical circuits and in probing atoms and molecules that vibrate thousands of trillions of times a second. But the standard method of pulse shaping—using devices known as spatial light modulators—is costly, bulky and lacks the fine control scientists increasingly need. In addition, these devices are typically based on liquid crystals that can be damaged by the very same pulses of high intensity laser light they were designed to shape.

    1
    Schematic shows a novel technique to reshape the properties of an ultrafast light pulse. An incoming pulse of light (left) is dispersed into its various constituent frequencies, or colors, and directed into a metasurface composed of millions of tiny silicon pillars and an integrated polarizer. The nanopillars are specifically designed to simultaneously and independently shape such properties of each frequency component as its amplitude, phase or polarization. The transmitted beam is then recombined to achieve a new shape-modified pulse (right). Credit: S. Kelley/NIST

    Now researchers at the National Institute of Standards and Technology (NIST) and the University of Maryland’s NanoCenter in College Park have developed a novel and compact method of sculpting light. They first deposited a layer of ultrathin silicon on glass, just a few hundred nanometers (billionths of a meter) thick, and then covered an array of millions of tiny squares of the silicon with a protective material. By etching away the silicon surrounding each square, the team created millions of tiny pillars, which played a key role in the light sculpting technique.

    The flat, ultrathin device is an example of a metasurface, which is used to change the properties of a light wave traveling through it. By carefully designing the shape, size, density and distribution of the nanopillars, multiple properties of each light pulse can now be tailored simultaneously and independently with nanoscale precision. These properties include the amplitude, phase and polarization of the wave.

    A light wave, a set of oscillating electric and magnetic fields oriented at right angles to each other, has peaks and troughs similar to an ocean wave. If you’re standing in the ocean, the frequency of the wave is how often the peaks or troughs travel past you, the amplitude is the height of the waves (trough to peak), and the phase is where you are relative to the peaks and troughs.

    “We figured out how to independently and simultaneously manipulate the phase and amplitude of each frequency component of an ultrafast laser pulse,” said Amit Agrawal, of NIST and the NanoCenter. “To achieve this, we used carefully designed sets of silicon nanopillars, one for each constituent color in the pulse, and an integrated polarizer fabricated on the back of the device.”

    When a light wave travels through a set of the silicon nanopillars, the wave slows down compared with its speed in air and its phase is delayed—the moment when the wave reaches its next peak is slightly later than the time at which the wave would have reached its next peak in air. The size of the nanopillars determines the amount by which the phase changes, whereas the orientation of the nanopillars changes the light wave’s polarization. When a device known as a polarizer is attached to the back of the silicon, the change in polarization can be translated to a corresponding change in amplitude.

    2

    A more detailed schematic of the pulse shaping setup. An incoming pulse of light (left) diffracts off a grating, which disperses the pulse into its various frequencies, or colors. A parabolic mirror then redirects the dispersed light into a silicon surface etched with millions of tiny pillars. The nanopillars are specifically designed to simultaneously and independently shape such properties of each frequency component as its amplitude, phase or polarization. A second parabolic mirror and diffraction grating then recombines the separated components into a newly formed pulse (right). Credit: T. Xu/Nanjing University

    Altering the phase, amplitude or polarization of a light wave in a highly controlled manner can be used to encode information. The rapid, finely tuned changes can also be used to study and change the outcome of chemical or biological processes. For instance, alterations in an incoming light pulse could increase or decrease the product of a chemical reaction. In these ways, the nanopillar method promises to open new vistas in the study of ultrafast phenomenon and high-speed communication.

    Agrawal, along with Henri Lezec of NIST and their collaborators, describe the findings online today in the journal Science.

    “We wanted to extend the impact of metasurfaces beyond their typical application—changing the shape of an optical wavefront spatially—and use them instead to change how the light pulse varies in time,” said Lezec.

    A typical ultrafast laser light pulse lasts for only a few femtoseconds, or one thousandth of a trillionth of a second, too short for any device to shape the light at one particular instant. Instead, Agrawal, Lezec and their colleagues devised a strategy to shape the individual frequency components or colors that make up the pulse by first separating the light into those components with an optical device called a diffraction grating.

    Each color has a different intensity or amplitude—similar to the way a musical overtone is composed of many individual notes that have different volumes. When directed into the nanopillar-etched silicon surface, different frequency components struck different sets of nanopillars. Each set of nanopillars was tailored to alter the phase, intensity or electric field orientation (polarization) of components in a particular way. A second diffraction grating then recombined all the components to create the newly shaped pulse.

    The researchers designed their nanopillar system to work with ultrafast light pulses (10 femtoseconds or less, equivalent to one hundredth of a trillionth of a second) composed of a broad range of frequency components that span wavelengths from 700 nanometers (visible red light) to 900 nanometers (near-infrared). By simultaneously and independently altering the amplitude and phase of these frequency components, the scientists demonstrated that their method could compress, split and distort pulses in a controllable manner.

    Further refinements in the device will give scientists additional control over the time evolution of light pulses and may enable researchers to shape in exquisite detail individual lines in a frequency comb, a precise tool for measuring the frequencies of light used in such devices as atomic clocks and for identifying planets around distant stars.

    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 March 22, 2019 Permalink | Reply
    Tags: , , NIST, Ultraviolet light-emitting diodes   

    From NIST: “NIST Researchers Boost Intensity of Nanowire LEDs” 


    From NIST

    March 21, 2019

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

    1
    Model of nanowire-based light-emitting diode showing that adding a bit of aluminum to the shell layer (black) directs all recombination of electrons and holes (spaces for electrons) into the nanowire core (multicolored region), producing intense light. Credit: NIST

    Nanowire gurus at the National Institute of Standards and Technology (NIST) have made ultraviolet light-emitting diodes (LEDs) that, thanks to a special type of shell, produce five times higher light intensity than do comparable LEDs based on a simpler shell design.

    Ultraviolet LEDs are used in a growing number of applications such as polymer curing, water purification and medical disinfection. Micro-LEDs are also of interest for visual displays. NIST staff are experimenting with nanowire-based LEDs for scanning-probe tips intended for electronics and biology applications.

    The new, brighter LEDs are an outcome of NIST’s expertise in making high-quality gallium nitride (GaN) nanowires. Lately, researchers have been experimenting with nanowire cores made of silicon-doped GaN, which has extra electrons, surrounded by shells made of magnesium-doped GaN, which has a surplus of “holes” for missing electrons. When an electron and a hole combine, energy is released as light, a process known as electroluminescence.

    The NIST group previously demonstrated GaN LEDs that produced light attributed to electrons injected into the shell layer to recombine with holes. The new LEDs have a tiny bit of aluminum added to the shell layer, which reduces losses from electron overflow and light reabsorption.

    As described in the journal Nanotechnology, the brighter LEDs are fabricated from nanowires with a so-called “p-i-n” structure, a tri-layer design that injects electrons and holes into the nanowire. The addition of aluminum to the shell helps confine electrons to the nanowire core, boosting the electroluminescence fivefold.

    “The role of the aluminum is to introduce an asymmetry in the electrical current that prevents electrons from flowing into the shell layer, which would reduce efficiency, and instead confines electrons and holes to the nanowire core,” first author Matt Brubaker said.

    The nanowire test structures were about 440 nanometers (nm) long with a shell thickness of about 40 nm. The final LEDs, including the shells, were almost 10 times larger. Researchers found that the amount of aluminum incorporated into fabricated structures depends on nanowire diameter.

    Group leader Kris Bertness said at least two companies are developing micro-LEDs based on nanowires, and NIST has a Cooperative Research and Development Agreement with one of them to develop dopant and structural characterization methods. The researchers have had preliminary discussions with scanning-probe companies about using NIST LEDs in their probe tips, and NIST plans to demonstrate prototype LED tools soon.

    The NIST team holds U.S. Patent 8,484,756 on an instrument that combines microwave scanning probe microscopy with an LED for nondestructive, contactless testing of material quality for important semiconductor nanostructures such as transistor channels and individual grains in solar cells. The probe could also be used for biological research on protein unfolding and cell structure.

    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 12:44 pm on November 29, 2018 Permalink | Reply
    Tags: , , NIST   

    From NIST: “NIST Atomic Clocks Now Keep Time Well Enough to Improve Models of Earth” 


    From NIST

    November 28, 2018

    Experimental atomic clocks at the National Institute of Standards and Technology (NIST) have achieved three new performance records, now ticking precisely enough to not only improve timekeeping and navigation, but also detect faint signals from gravity, the early universe and perhaps even dark matter.

    The clocks each trap a thousand ytterbium atoms in optical lattices, grids made of laser beams. The atoms tick by vibrating or switching between two energy levels. By comparing two independent clocks, NIST physicists achieved record performance in three important measures: systematic uncertainty, stability and reproducibility.

    2

    NIST physicist Andrew Ludlow and colleagues achieved new atomic clock performance records in a comparison of two ytterbium optical lattice clocks. Laser systems used in both clocks are visible in the foreground, and the main apparatus for one of the clocks is located behind Ludlow.
    Credit: Burrus/NIST

    Published online today in the journal Nature, the new NIST clock records are:

    Systematic uncertainty: How well the clock represents the natural vibrations, or frequency, of the atoms. NIST researchers found that each clock ticked at a rate matching the natural frequency to within a possible error of just 1.4 parts in 1018—about one billionth of a billionth.
    Stability: How much the clock’s frequency changes over a specified time interval, measured to a level of 3.2 parts in 1019 (or 0.00000000000000000032) over a day.
    Reproducibility: How closely the two clocks tick at the same frequency, shown by 10 comparisons of the clock pair, yielding a frequency difference below the 10-18 level (again, less than one billionth of a billionth).

    “Systematic uncertainty, stability, and reproducibility can be considered the ‘royal flush’ of performance for these clocks,” project leader Andrew Ludlow said. “The agreement of the two clocks at this unprecedented level, which we call reproducibility, is perhaps the single most important result, because it essentially requires and substantiates the other two results.”

    “This is especially true because the demonstrated reproducibility shows that the clocks’ total error drops below our general ability to account for gravity’s effect on time here on Earth. Hence, as we envision clocks like these being used around the country or world, their relative performance would be, for the first time, limited by Earth’s gravitational effects.”

    Einstein’s theory of relativity predicts that an atomic clock’s ticking, that is, the frequency of the atoms’ vibrations, is reduced—shifted toward the red end of the electromagnetic spectrum—when observed in stronger gravity. That is, time passes more slowly at lower elevations.

    While these so-called redshifts degrade a clock’s timekeeping, this same sensitivity can be turned on its head to exquisitely measure gravity. Super-sensitive clocks can map the gravitational distortion of space-time more precisely than ever. Applications include relativistic geodesy, which measures the Earth’s gravitational shape, and detecting signals from the early universe such as gravitational waves and perhaps even as-yet-unexplained dark matter.

    NIST’s ytterbium clocks now exceed the conventional capability to measure the geoid, or the shape of the Earth based on tidal gauge surveys of sea level. Comparisons of such clocks located far apart such as on different continents could resolve geodetic measurements to within 1 centimeter, better than the current state of the art of several centimeters.

    In the past decade of new clock performance records announced by NIST and other labs around the world, this latest paper showcases reproducibility at a high level, the researchers say. Furthermore, the comparison of two clocks is the traditional method of evaluating performance.

    Among the improvements in NIST’s latest ytterbium clocks was the inclusion of thermal and electric shielding, which surround the atoms to protect them from stray electric fields and enable researchers to better characterize and correct for frequency shifts caused by heat radiation.

    The ytterbium atom is among potential candidates for the future redefinition of the second—the international unit of time—in terms of optical frequencies. NIST’s new clock records meet one of the international redefinition roadmap’s requirements, a 100-fold improvement in validated accuracy over the best clocks based on the current standard, the cesium atom, which vibrates at lower microwave frequencies.

    NIST is building a portable ytterbium lattice clock with state-of-the-art performance that could be transported to other labs around the world for clock comparisons and to other locations to explore relativistic geodesy techniques.

    The work is supported by NIST, the National Aeronautics and Space Administration and the Defense Advanced Research Projects Agency.

    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.

     
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