In This Issue...
NIST Researchers Create 'Quantum Cats' Made of Light
Researchers at the National Institute of Standards and Technology (NIST) have created "quantum cats" made of photons (particles of light), boosting prospects for manipulating light in new ways to enhance precision measurements as well as computing and communications based on quantum physics.
The NIST experiments, described in a forthcoming paper,* repeatedly produced light pulses that each possessed two exactly opposite properties—specifically, opposite phases, as if the peaks of the light waves were superimposed on the troughs. Physicists call this an optical Schrödinger's cat. NIST's quantum cat is the first to be made by detecting three photons at once and is one of the largest and most well-defined cat states ever made from light. (Larger cat states have been created in different systems by other research groups, including one at NIST.)
A "cat state" is a curiosity of the quantum world, where particles can exist in "superpositions" of two opposite properties simultaneously. Cat state is a reference to German physicist Erwin Schrödinger's famed 1935 theoretical notion of a cat that is both alive and dead simultaneously.
"This is a new state of light, predicted in quantum optics for a long time," says NIST research associate Thomas Gerrits, lead author of the paper. "The technologies that enable us to get these really good results are ultrafast lasers, knowledge of the type of light needed to create the cat state, and photon detectors that can actually count individual photons."
The NIST team created their optical cat state by using an ultrafast laser pulse to excite special crystals to create a form of light known as a squeezed vacuum, which contains only even numbers of photons. A specific number of photons were subtracted from the squeezed vacuum using a device called a beam splitter. The photons were identified with a NIST sensor that efficiently detects and counts individual photons (see "NIST Detector Counts Photons With 99 Percent Efficiency," NIST Tech Beat, Apr. 13, 2010, at www.nist.gov/eeel/optoelectronics/detector_041310.cfm.) Depending on the number of subtracted photons, the remaining light is in a state that is a good approximation of a quantum cat says Gerrits—the best that can be achieved because nobody has been able to create a "real" one, by, for instance, the quantum equivalent to superimposing two weak laser beams with opposite phases.
NIST conducts research on novel states of light because they may enhance measurement techniques such as interferometry, used to measure distance based on the interference of two light beams. The research also may contribute to quantum computing—which may someday solve some problems that are intractable today—and quantum communications, the most secure method known for protecting the privacy of a communications channel. Larger quantum cats of light are needed for accurate information processing.
* T. Gerrits, S. Glancy, T. Clement , B. Calkins, A. Lita, A. Miller, A. Migdall, S.W. Nam, R. Mirin and E. Knill. Generation of optical coherent state superpositions by number-resolved photon subtraction from squeezed vacuum. Physical Review A. Forthcoming.
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Yikes! NIST Sensor Measures Yoctonewton Forces Fast
Physicists at the National Institute of Standards and Technology (NIST) have used a small crystal of ions (electrically charged atoms) to detect forces at the scale of yoctonewtons. Measurements of slight forces—one yoctonewton is equivalent to the weight of a single copper atom on Earth—can be useful in force microscopy, nanoscale science, and tests of fundamental physics theories.
A newton is already a small unit: roughly the force of Earth's gravity on a small apple. A yoctonewton is one septillionth of a newton (yocto means 23 zeros after the decimal place, or 0.000000000000000000000001).
Measurements of vanishingly small forces typically are made with tiny mechanical oscillators, which vibrate like guitar strings. The new NIST sensor, described in Nature Nanotechnology,* is even more exotic—a flat crystal of about 60 beryllium ions trapped inside a vacuum chamber by electromagnetic fields and cooled to 500 millionths of a degree above absolute zero with an ultraviolet laser. The apparatus was developed over the past 15 years for experiments related to ion plasmas and quantum computing. In this case, it was used to measure yoctonewton-scale forces from an applied electric field. In particular, the experiment showed that it was possible to measure about 390 yoctonewtons in just one second of measurement time, a rapid speed that indicates the technique's high sensitivity. Sensitivity is an asset for practical applications.
The previous force measurement record with this level of sensitivity was achieved by another NIST physicist who measured forces 1,000 times larger, or 500 zeptonewtons (0.0000000000000000005 newtons) in one second of measurement time using a mechanical oscillator.** Previous NIST research indicated that a single trapped ion could sense forces at yoctonewton scales but did not make calibrated measurements. ***
The ion sensor described in Nature Nanotechnology works by examining how an applied force affects ion motion, based on changes in laser light reflected off the ions. A small oscillating electric field applied to the crystal causes the ions to rock back and forth; as the ions rock, the intensity of the reflected laser light wobbles in sync with the ion motion. A change in the amount of reflected laser light due to the force is detectable, providing a measure of the ions' induced motion using a principle similar to the one at work in a police officer's radar gun. The technique is highly sensitive because of the low mass of the ions, strong response of charged particles to external electric fields, and ability to detect nanometer-scale changes in ion motion.
The research was funded in part by the Defense Advanced Research Projects Agency. The first author, M.J. Biercuk, did the work as a post-doctoral researcher at NIST and is now at the University Sydney in Australia. Co-author H. Uys did the work as a NIST guest researcher and has since returned to the Council for Scientific and Industrial Research, Pretoria, South Africa.
* M.J. Biercuk, H. Uys, J.P. Britton, A.P. VanDevender and J. J. Bollinger. Ultrasensitive force and displacement detection using trapped ions. Nature Nanotechnology. Posted online Aug. 22, 2010.
** J.D. Teufel, T. Donner, M.A. Castellanos-Beltran, J.W. Harlow and K.W. Lehnert. Nanomechanical motion measured with an imprecision below that at the standard quantum limit. Nature Nanotechnology 4, 820–823.
*** See TechBeat article "NIST Develops Novel Ion Trap for Sensing Force and Light," NIST Tech Beat, June 30, 2009, at www.nist.gov/public_affairs/techbeat/tb2009_0630.htm#trap.
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Glasperlenspiel: NIST Scientists Propose New Test for Gravity
A new experiment proposed* by physicists at the National Institute of Standards and Technology (NIST) may allow researchers to test the effects of gravity with unprecedented precision at very short distances—a scale at which exotic new details of gravity's behavior may be detectable.
Of the four fundamental forces that govern interactions in the universe, gravity may be the most familiar, but ironically it is the least understood by physicists. While gravity's influence is well-documented on bodies separated by astronomical or human-scale distances, it has been largely untested at very close scales—on the order of a few millionths of a meter—where electromagnetic forces often dominate. This lack of data has sparked years of scientific debate.
"There are lots of competing theories about whether gravity behaves differently at such close range," says NIST physicist Andrew Geraci, "But it's quite difficult to bring two objects that close together and still measure their motion relative to each other very precisely."
In an attempt to sidestep the problem, Geraci and his co-authors have envisioned an experiment that would suspend a small glass bead in a laser beam "bottle," allowing it to move back and forth within the bottle. Because there would be very little friction, the motion of the bead would be exquisitely sensitive to the forces around it, including the gravity of a heavy object placed nearby.
According to the research team, the proposed experiment would permit the testing of gravity's effects on particles separated by 1/1,000 the diameter of a human hair, which could ultimately allow Newton's law to be tested with a sensitivity 100,000 times better than existing experiments.
Actually realizing the scheme—detailed in a new paper in Physical Review Letters—could take a few years, co-author Scott Papp says, in part because of trouble with friction, the old nemesis of short-distance gravity research. Previous experiments have placed a small object (like this experiment's glass bead) onto a spring or short stick, which have created much more friction than laser suspension would introduce, but the NIST team's idea comes with its own issues.
"Everything creates some sort of friction," Geraci says. "We have to make the laser beams really quiet, for one thing, and then also eliminate all the background gas in the chamber. And there will undoubtedly be other sources of friction we have not yet considered."
For now, Geraci says, the important thing is to get the idea in front of the scientific community.
"Progress in the scientific community comes not just from individual experiments, but from new ideas," he says. "The recognition that this system can lead to very precise force measurements could lead to other useful experiments and instruments."
* A.A. Geraci, S.B. Papp and J. Kitching. Short-range force detection using optically cooled levitated microspheres. Physical Review Letters, Aug. 30, 2010 (online). 105, 101101 (2010) DOI: 10.1103/PhysRevLett.105.101101
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Micro Rheometer is Latest Lab On a Chip Device
Researchers at the National Institute of Standards and Technology (NIST) have demonstrated a microminiaturized device that can make complex viscosity measurements—critical data for a wide variety of fields dealing with things that have to flow—on sample sizes as small as a few nanoliters. Currently a table-top prototype, the NIST rheometer could be a particularly valuable tool for biotechnologists studying minute quantities of complex materials that must function in confined spaces.
Viscosity, elasticity and how materials flow when subject to a force is the subject of rheology, and the measurements tell a lot about a complicated material like a gel. Is it more like a liquid or a solid? By how much and under what conditions? The popular toy Silly Putty™ is a classic example of complex viscoelasticity, bouncing better than a rubber ball under a sharp, sudden force but slumping into a puddle when left alone.
One common way to make dynamic rheology measurements (how behavior changes with the speed or frequency of the applied force) is with a sizeable lab instrument that traps a test sample between a fixed plate and one that moves, and measures how much the thin layer of test material resists being deformed. Typical sample sizes are around a couple of milliliters, which doesn't sound like much, but, says polymer scientist Gordon Christopher, for some researchers it's a whole bunch.
"A lot of people in the biosciences are making very complex designer fluids based on proteins where you might make only 10 milliliters at a time. Polypeptide hydrogels for drug delivery or tissue replacement, for example," Christopher explains. "Their flow behaviors are very complicated and you really need to understand them, but in a traditional rheometer your sample for a single test is a large percentage of what you just spent two months making."
Inspired by a talk by a NIST scientist working on the design of novel nano positioning microelectromechanical systems (MEMS), team leader Kalman Migler and his colleagues began a collaboration to build a MEMS device that duplicated a classic sliding-plate dynamic rheometer—but in a space about one-twentieth the size of a postage stamp. The sample size of the MEMS rheometer is about 5 nanoliters. "With our device, if you gave me a milliliter of sample, I could give you back hundreds of tests," Christopher says.
Equally as important, he says, the MEMS rheometer inherently tests materials when they are confined in a very small space. For many biological applications where the material is meant to be used in a confined region like a blood vessel or the interior of a cell—or must be injected through a thin needle—understanding the flow characteristics of small amounts in a small space is more important than knowing how it behaves in bulk.
NIST's early prototype MEMS rheometers include only the core sliding plate mechanism on the MEMS chip, and rely on a microscope and high-speed cameras for the actual measurements. In a more polished version, according to the research team, the necessary sensors could be included on the chip and the entire instrument reduced to a handheld device for, e.g., quality control measurements on a plant floor. The NIST MEMS dynamic rheometer is described in a new paper in Lab on a Chip.*
* G.F. Christopher, J.M. Yoo, N. Dagalakis, S.D. Hudson and K.B. Migler. Development of aMEMS based dynamic rheometer. Lab Chip, 2010, Advance Article. DOI: 10.1039/C005065B.
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The Perfect Nanocube: Precise Control of Size, Shape, and Composition
With growing interest in using nanoparticles for everything from antibacterial socks to medical imaging to electronic devices, the need to understand the environmental, health and safety risks of these particles also grows. Researchers at the National Institute of Standards and Technology (NIST) have developed a simple process for producing nanocrystals that will enable studies of certain physical and chemical properties that affect how nanoparticles interact with the world around them.
Because nanoparticles behave differently from bulk samples of the same material, new tests to understand how they affect biological systems must be developed. Toxicologists determine the hazards posed by nanoparticles by introducing them to a biological system and monitoring the effects, but they currently lack a set of control particles whose size, shape and composition have been carefully produced and characterized.
In a recent paper published in Angewandte Chemie,* NIST scientists describe a one-step process that allows them to control the size, shape and composition of gold-copper alloy nanocrystals to create perfect-edged nanocubes as small as 3.4 nanometers—just half the thickness of a cell wall and on the same size range as DNA.
The researchers combined and heated gold and copper precursors with other chemicals to produce highly crystalline, homogeneous, perfect nanocubes with abundant yield. To study the formation process, they removed samples at 1 hour, 1.5 hours, 5 hours, and 24 hours and found that just five hours were needed to produce perfectly cubic nanoparticles of uniform size. By adjusting the ratios of the chemicals in the original solution and the reaction time, they were able to precisely control the size, shape and composition of the nanocubes. This process is unique in allowing control of the ratio of copper to gold atoms within the nanocube to either 3:1 or 1:3.
"It's a simple process, and to the best of our knowledge is the first to use synthetic chemistry, or 'bottom up' technology, to produce gold-containing nanocubes below 5 nanometers. Anything less than 10 nanometers has been extremely challenging due to the mobile behavior of the gold atoms," says NIST physicist Angela R. Hight Walker, who wrote the paper with Yonglin Liu, a guest researcher at NIST.
The NIST-developed process for creating such nanocubes will allow toxicologists to systematically alter one of the nanocubes' characteristics and observe how the change affects the biological response, if at all.
This synthesis and the resulting high-quality nanocubes may have other applications in areas such as solar energy, says Liu. "Typically, we cannot make big batches of high-quality samples for testing; now we can."
The perfect-edged nanocubes are unique from other nanocubes in the literature, says Hight Walker. The sharp edges, as opposed to truncated or rounded edges, will enable different, more reactive chemistry that could be beneficial in applications such as catalysis—in which the nanocubes would be used to initiate or enhance a chemical reaction.
*Y. Liu and A.R. Hight Walker. Monodisperse gold-copper bimetallic nanocubes: facile one-step synthesis with controllable size and composition. Angewandte Chemie. Posted online Aug. 16, 2010.
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Manufacturing Extension Partnership Awards Grant to Support Green Building Technologies
The National Institute of Standards and Technology (NIST) Hollings Manufacturing Extension Partnership (MEP) has awarded a grant of $1.5 million over 3 years to the Delaware Valley Industrial Resources Center (DVIRC) and the New Jersey Manufacturing Extension Partnership (NJMEP), the MEP affiliate centers in Philadelphia and New Jersey, to encourage expanded manufacturing of energy-efficient building technologies.
The grant complements a larger U.S. Department of Energy project announced on August 24, 2010, that provides up to $122 million to the Pennsylvania State University for an Energy Innovation Hub. To be located at the Philadelphia Navy Yard Clean Energy campus, the Hub will focus on developing energy-efficient building designs that will save energy, cut pollution, and position the United States as a leader in this industry.
According to MEP, this project represents the first time that federal, state, and local public and private resources will be pooled to create a formal applied research/manufacturing cluster that spans from the lab bench, through production to implementation.
“Expanding the capabilities of U.S. manufacturers to respond to the market opportunities resulting from the development of new energy-efficient building technologies is key to ensuring the linkage between R&D and commercial application,” says Roger Kilmer, director of the NIST MEP.
DVIRC and NJMEPs role will be to connect manufacturers, specifically small and mid-size enterprises (SMEs) to the project at all levels, including R&D, design and testing of new products, materials, technologies, and systems, and, more importantly, commercializing those opportunities for business growth and job creation.
The Energy Innovation Hub will pursue a research, development and demonstration (RD&D) program targeting technologies for single buildings and district-wide systems. These new building systems and components will need to be manufactured, presenting a unique opportunity for businesses in the area to get in on the ground floor.
The DVIRC in collaboration with its sister-center, the NJMEP, will leverage their knowledge of and relationships with regional companies to identify technologies such as sensors, new building materials, and computer simulation tools developed by the Energy Innovation Hub, and translate them into components they can license, develop and manufacture.
“Our region is home to a significant asset and essential resource to innovate new products and technologies,” says Joe Houldin, CEO of DVIRC. “SME manufacturers are true innovators and contribute substantial value to the region’s economic prosperity, and will play a vital role in taking energy research and applied technology to market.”
“We hope that this effort will be a model for public-private collaborative partnerships across the nation,” says Aimee Dobrzeniecki, deputy director of the NIST MEP.
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Annual IT Security Automation Conference Runs Sept. 27-29
The Sixth Annual IT Security Automation Conference, co-hosted by the National Institute of Standards and Technology (NIST), focuses on applying and integrating emerging cyber security automation technologies and software assurance into a wide range of application areas such as cloud computing, health care information technology and compliance. The conference will be held Sept. 27-29, 2010, at the Baltimore Convention Center.
Keynote speakers include White House Cybersecurity Coordinator Howard Schmidt and Intel Senior Fellow Stephen S. Pawlowski, chief technology officer for the Intel Architecture Group and general manager for Central Architecture and Planning for Intel Corp. Security automation embraces a variety of computing tools based on standards and specifications to reduce the complexity and time necessary to manage vulnerabilities, measure security, and ensure compliance.
This year’s conference will focus on specific open standards and new security technologies as they apply to several high-interest areas, including:
NIST, the Department of Homeland Security (DHS), the National Security Agency (NSA) and the Defense Information Systems Agency (DISA) co-host this annual event. The four agencies are actively involved in automating computer security.
The IT Security Automation Conference is geared toward public and private-sector executives, security managers and staff, information technology (IT) professionals and developers of products and services with a common understanding for using specific open standards and new security technologies.
A trade show runs concurrently with the conference and includes more than 30 vendors demonstrating available security automation packages. More information, including registration, is available at http://www.nist.gov/itl/csd/2010-scap-conference.cfm. Reporters interested in attending should contact Evelyn Brown, (301) 975-5661.
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New Material May Reveal Inner Workings of Hi-temp Superconductors
Measurements taken* at the National Institute of Standards and Technology (NIST) may help physicists develop a clearer understanding of high-temperature superconductors, whose behavior remains in many ways mysterious decades after their discovery. A new copper-based compound exhibits properties never before seen in a superconductor and could be a step toward solving part of the mystery.
Copper-based high-temperature superconductors are created by taking a nonconducting material called a Mott insulator and either adding or removing some electrons from its crystal structure. As the quantity of electrons is raised or lowered, the material undergoes a gradual transformation to one that, at certain temperatures, conducts electricity utterly without resistance. Until now, all materials that fit the bill could only be pushed toward superconductivity either by adding or removing electrons—but not both.
However, the new material tested at the NIST Center for Neutron Research (NCNR) is the first one ever found that exhibits properties of both of these regimes. A team of researchers from Osaka University, the University of Virginia, the Japanese Central Research Institute of Electric Power Industry, Tohoku University and the NIST NCNR used neutron diffraction to explore the novel material, known only by its chemical formula of YLBLCO.
The material can only be made to superconduct by removing electrons. But if electrons are added, it also exhibits some properties only seen in those materials that superconduct with an electron surplus—hinting that scientists may now be able to study the relationship between the two ways of creating superconductors, an opportunity that was unavailable before this “ambipolar” material was found.
The results are described in detail in a “News and Views” article in the August, 2010, issue of Nature Physics, “Doped Mott insulators: Breaking through to the other side.”**
* K. Segawa , M. Kofu, S.-H. Lee, I. Tsukada. H. Hiraka, M. Fujita, S. Chang, K. Yamada and Y. Ando. Zero-Doping State and Electron-Hole Asymmetry in an Ambipolar Cuprate. Nature Physics, August 2010, pp. 579-583, DOI 10.1038/NPHYS1717.
** J. Orenstein and A. Vishwanath. Doped Mott insulators: Breaking through to the other side. Nature Physics, V. 6, August, 2010. DOI:10.1038/nphys1751.
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NIST Ultraviolet Source Helps NASA Spacecraft Measure the Origins of Space Weather
With a brilliant, finely tuned spark of ultraviolet (UV) light, a physicist at the National Institute of Standards and Technology (NIST) helped NASA scientists successfully position a crucial UV sensor inside a space-borne instrument to observe a “hidden” layer of the Sun where violent space weather can originate.
Dark spots on the Sun release particles and electromagnetic fields into space. As these particles and fields pass through the Sun’s “transition region,” 5,000 kilometers above the surface, they can gather considerable steam, resulting in violent episodes of “space weather” that can damage Earth-orbiting satellites and disrupt electronic communications.
The powerful magnetic fields in the transition region can be studied indirectly, by observing the UV light emanating from that region. The fields slightly shift the colors (wavelengths) of UV light released by charged atoms (ions) in their vicinity. Measuring how much these wavelengths shift can yield information on the magnetic field’s strength.
The catch is you can’t do it from Earth, where the atmosphere absorbs the UV light, so a team at NASA Marshall Space Flight Center in Huntsville, Ala., constructed a rocket-borne instrument, known as the Solar Ultraviolet Magnetograph Investigation (SUMI), designed to take pictures of these magnetic fields from space.
SUMI observes shifts in the well-known wavelengths of UV light emitted by magnesium and carbon ions caught in the magnetic fields of the transition region. The instrument’s optics break down the incoming UV light into a spectrum of individual wavelengths and fans them out, much as a prism fans out white light into a rainbow. The trick is in knowing precisely which wavelength falls where in the instrument and adjusting it so that the desired wavelengths land on the instrument’s detectors.
“The problem is that SUMI’s detectors are small, so they don’t capture a wide range of wavelengths,” says NIST physicist Joseph Reader. “The issue becomes how to align the complicated optics in the instrument so that the magnesium and carbon lines are recorded on its detectors. The solution is to get a light source that can produce these same lines in the laboratory,” he says, and use them to properly adjust the instrument's sensors.
Readily available lamps can simulate the UV light from the singly ionized magnesium, but generating the UV light from triply ionized carbon (carbon with three electrons removed) is difficult. Enter NIST’s unique “sliding spark source.” It consists of a pair of graphite electrodes with a quartz surface in between. A spark from these electrodes glides along the quartz surface, controllably producing the desired wavelengths of UV light from ionized carbon. Inside a clean room in Huntsville, UV radiation from the spark source entered SUMI, enabling its sensors to be accurately positioned before deployment.
On July 30, 2010, SUMI was successfully launched from White Sands, N.M. It rocketed 320 km in space and observed sunspot 11092 for about 6 minutes before parachuting back to earth. The Huntsville team is analyzing the data it obtained.
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Washington Metro Region Nanotechnology Partnership Forum at NIST
On Sept. 13, 2010, the National Institute of Standards and Technology (NIST), the Federal Laboratory Consortium, the Maryland Technology Development Corporation (TEDCO) and the Montgomery County Department of Economic Development will co-sponsor a nanotechnology forum on NIST’s Gaithersburg, Md., campus. Participating organizations also will include the Food and Drug Administration, the National Institutes of Health, NASA, Cytimmune Sciences, MITRE, The Johns Hopkins University and Lockheed Martin.
Attendees will have the opportunity to meet researchers from federal agencies and laboratories, academia and private-sector firms looking for potential partners in nanotechnology and learn about the unique resources available in the Washington metro region. Presentations and poster sessions will include biomedical nanotechnology applications, advanced materials and manufacturing, and nanoelectronics. Other topics will include commercializing emerging technologies and how to connect with regional resources such as federal labs, universities and private sector firms. In addition, a panel discussion will take place featuring members of the nanotechnology industry.
The registration deadline for U.S. citizens has been extended until noon, Wednesday, Sept. 8, 2010. A registration fee of $20 includes refreshments and lunch. Non-U.S. citizens who wish to attend should contact Cathy Cohn, firstname.lastname@example.org, (301) 975-6691.
For other inquiries, contact John Emond, email@example.com, (202) 358-1686.
To register and view the agenda, go to http://www.eventbrite.com/event/734215057.
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