In This Issue...
X Marks the Spot: Ions Coldly Go Through NIST Trap Junction
Physicists at the National Institute of Standards and Technology (NIST) have demonstrated a new ion trap that enables ions to go through an intersection while keeping their cool. Ten million times cooler than in prior similar trips, in fact. The demonstration, described in a forthcoming paper in Physical Review Letters,* is a step toward scaling up trap technology to build a large-scale quantum computer using ions (electrically charged atoms), a potentially powerful machine that could perform certain calculations—such as breaking today’s best data encryption codes—much faster than today’s computers.
NIST’s new trap with a junction solves a key engineering issue for future possible ion-trap quantum computers: how to move ions in a particular quantum mechanical state back and forth between different locations for data storage or logic operations, without heating them up so much that they lose their fragile quantum properties, which are critical to information processing.
The new ion trap, a rectangle roughly 5 by 2 millimeters in outer dimensions, was constructed from laser-machined alumina, with a gold coating to form electrodes. It is more complex than previous NIST ion traps, with 46 electrodes supporting 18 ion trapping zones. Its unique feature is an X-shaped bridge connecting electrodes across a junction between zones. Junctions are required to allow ions to be grouped together efficiently for logic operations. As voltages are applied to different electrodes to move the ions, the electric fields restrain an ion as it moves between trapping zones. The fields created by the X-bridge are required for smooth transport through the junction and to keep ions from popping out at the junction.
NIST scientists transported single beryllium ions through the X-junction more than 1 million times while maintaining the properties critical to information processing with greater than 99.99 percent success. Pairs of ions were transported over 100,000 times. Ion transport through a junction has been reported once before, but the ions in the NIST trap received over 10 million times less heat than the earlier effort. The low heating, achieved through careful control and reductions in electrical noise, minimizes a major source of computation errors and processing slowdowns.
Over the past 15 years, NIST has demonstrated the basic building blocks for a computer based on ion traps, a promising design for a quantum computer. Now, the latest demonstration shows how information might be moved through a quantum processor rapidly and reliably enough for computing. It takes about 20 microseconds to move an ion across the junction and about 50 to 100 microseconds for transport between zones—times compatible with logic operations using ions. The trap design makes large-scale information processing possible while keeping the number of ions in each trap zone relatively small, such that individual ions can be manipulated without unwanted effects.
The work was funded in part by the Intelligence Advanced Research Projects Agency and Office of Naval Research.
* R.B. Blakestad, C. Ospelkaus, A.P. VanDevender, J.M. Amini, J. Britton, D. Leibfried, and D.J. Wineland. High fidelity transport of trapped-ion qubits through an X-junction trap array. Physical Review Letters. Forthcoming.
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Quantum Computers Will Require Complex Software to Manage Errors
Highlighting another challenge to the development of quantum computers, theorists at the National Institute of Standards and Technology (NIST) have shown* that a type of software operation, proposed as a solution to fundamental problems with the computers’ hardware, will not function as some designers had hoped.
Quantum computers—if they can ever be realized—will employ effects associated with atomic physics to solve otherwise intractable problems. But the NIST team has proved that the software in question, widely studied due to its simplicity and robustness to noise, is insufficient for performing arbitrary computations. This means that any software the computers use will have to employ far more complex and resource-intensive solutions to ensure the devices function effectively.
Unlike a conventional computer’s binary on-off switches, the building blocks of quantum computers, known as quantum bits, or “qubits,” have the mind-bending ability to exist in both “on” and “off” states simultaneously due to the so-called “superposition” principle of quantum physics. Once harnessed, the superposition principle should allow quantum computers to extract patterns from the possible outputs of a huge number of computations without actually performing all of them. This ability to extract overall patterns makes the devices potentially valuable for tasks such as codebreaking.
One issue, though, is that prototype quantum processors are prone to errors caused, for example, by noise from stray electric or magnetic fields. Conventional computers can guard against errors using techniques such as repetition, where the information in each bit is copied several times and the copies are checked against one another as the calculation proceeds. But this sort of redundancy is impossible in a quantum computer, where the laws of the quantum world forbid such information cloning.
To improve the efficiency of error correction, researchers are designing quantum computing architectures so as to limit the spread of errors. One of the simplest and most effective ways of ensuring this is by creating software that never permits qubits to interact if their errors might compound one another. Quantum software operations with this property are called “transversal encoded quantum gates.” NIST information theorist Bryan Eastin describes these gates as a solution both simple to employ and resistant to the noise of error-prone quantum processors. But the NIST team has proved mathematically that transversal gates cannot be used exclusively, meaning that more complex solutions for error management and correction must be employed.
Eastin says their result does not represent a setback to quantum computer development because researchers, unable to figure out how to employ transversal gates universally, have already developed other techniques for dealing with errors. “The findings could actually help move designers on to greener pastures,” he says. “There are some avenues of exploration that are less tempting now.”
* B. Eastin and E. Knill. Restrictions on transversal quantum gate sets. Physical Review Letters, 102, 110502, March 20, 2009.
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Nano Changes Rise to Macro Importance in a Key Electronics Material
By combining the results of a number of powerful techniques for studying material structure at the nanoscale, a team of researchers from the National Institute of Standards and Technology (NIST), working with colleagues in other federal labs and abroad, believe they have settled a long-standing debate over the source of the unique electronic properties of a material with potentially great importance for wireless communications.
The new study* of silver niobate not only opens the door to engineering improved electronic components for smaller, higher performance wireless devices, but also serves as an example of understanding how subtle nanoscale features of a material can give rise to major changes in its physical properties.
Silver niobate is a ceramic dielectric, a class of materials used to make capacitors, filters and other basic components of wireless communications equipment and other high-frequency electronic devices. A useful dielectric needs to have a large dielectric constant—roughly, a measure of the material’s ability to hold an electric charge—that is stable in the operating temperature range. The material also should have low dielectric losses—which means that it does not waste energy as heat and preserves much of its intended signal strength. In the important gigahertz range of the radio spectrum—used for a wide variety of wireless applications—silver niobate-based ceramics are the only materials known that combine a high, temperature-stable dielectric constant with sufficiently low dielectric losses.
It’s been known for some time that silver niobate’s unique dielectric properties are temperature dependent—the dielectric constant peaks in a broad range near room temperature in these ceramics, which makes them suitable for practical applications. Earlier studies were unable to identify the structural basis of the unusual dielectric response because no accompanying changes in the overall crystal structure could be observed. “The crystal symmetry doesn’t seem to change at those temperatures,” explains NIST materials scientist Igor Levin, “but that’s because people were using standard techniques that tell you the average structure. The important changes happen at the nanoscale and are lost in averages.”
Only in recent years, says Levin, have the specialized instruments and analytic techniques been available to probe nanoscale structural changes in crystals. Even so, he says, “these subtle deviations from the average are so small that any single measurement gives only partial information on the structure. You need to combine several complementary techniques that look at different angles of the problem.” Working at different facilities** the team combined results from several high-resolution probes using X-rays, neutrons and electrons—tools that are sensitive to both the local and average crystal structure— to understand silver niobate’s dielectric properties. The results revealed an intricate interplay between the oxygen atoms, arranged in an octahedral pattern that defines the compound’s crystal structure, and the niobium atoms at the centers of the octahedra.
At high temperatures, the niobium atoms are slightly displaced, but their average position remains in the center—so the shift isn’t seen in averaging measurements. As the compound cools, the oxygen atoms cooperate by moving a little, causing the octahedral structure to rotate slightly. This movement generates strain which “locks” the niobium atoms into off-centered positions—but not completely. The resulting partial disorder of the niobium atoms gives rise to the dielectric properties. The results, the researchers say, point to potential avenues for engineering similar properties in other compounds.
The work was supported in part by the U.S. Department of Energy and the U.K. Science and Technology Facilities Council.
* I. Levin, V. Krayzman, J.C. Woicik, J. Karapetrova, T. Proffen, M.G. Tucker and I.M. Reaney. Structural changes underlying the diffuse dielectric response in AgNbO3. Phys. Rev. B 79, 104113, posted online March 26, 2009.
** The study required measurements at the Advanced Photon Source at Argonne National Laboratory, the Lujan Neutron Center at Los Alamos National Laboratory and the ISIS Pulsed Neutron and Muon Source at Rutherford Appleton Laboratory (United Kingdom). In addition to NIST, researchers from Argonne, Los Alamos, ISIS and the University of Sheffield contributed to the paper.
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NIST Awards Contract for Work on Smart Grid Interim Standards
As part of the Obama Administration’s commitment to moving the nation toward energy independence, the National Institute of Standards and Technology (NIST) has contracted with the Electric Power Research Institute, Inc. (EPRI) to help it develop an interim “roadmap” for determining the architecture and initial key standards for an electric power “Smart Grid”.
The planned Smart Grid is a nationwide network that uses information technology to deliver electricity efficiently, reliably and securely. To facilitate progress toward a modernized electric-power system that is cleaner, more resilient and accommodates alternative sources of energy, Congress assigned NIST “primary responsibility to coordinate development of a framework that includes protocols and model standards for information management to achieve interoperability of Smart Grid devices and systems.”
EPRI will assist in identifying issues and priorities for developing permanent interoperability standards. Headquartered in Palo Alto, Calif., EPRI is an independent, nonprofit, noncommercial organization that conducts research and development relating to the generation, delivery and use of electricity.
“The Smart Grid is a cornerstone of national efforts to achieve energy independence, save consumers money and curb greenhouse gas emissions,” said NIST Deputy Director Patrick Gallagher. “This contract is a significant step in the urgent effort to identify and develop standards that will ensure a reliable and robust Smart Grid.”
EPRI also will support consensus-building activities that will provide the basis for the initial slate of Smart Grid standards. NIST will soon announce a three-phase plan that will result in an end-of-year submission for approval of standards to the Federal Energy Regulatory Commission, which has jurisdiction over interstate distribution and sales of electric power.
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World’s First Nanofluidic Device with Complex 3-D Surfaces Built
Researchers at the National Institute of Standards and Technology (NIST) and Cornell University have capitalized on a process for manufacturing integrated circuits at the nanometer (billionth of a meter) level to engineer the first-ever nanoscale fluidic device with complex three-dimensional surfaces. As described in a recent paper in the journal Nanotechnology,* the Lilliputian chamber is a prototype for future tools with custom-designed surfaces to manipulate and measure different types of nanoparticles in solution.
Among the potential applications are processing nanoscale materials for manufacturing products such as pharmaceuticals, sorting mixtures of nanoparticles for environmental health and safety investigations, and isolating and confining individual DNA strands for scientific study.
Nanofluidic devices are usually fabricated by etching tiny channels into a glass or silicon wafer with the same “lithographic” procedures used for making integrated circuits. To date, these flat rectangular channels have had simple surfaces with only a few depths. This limits their ability to separate mixtures of nanoparticles with different sizes or study the nanoscale behavior of biomolecules (such as DNA) in detail.
To solve the problem, the researcher team developed a lithographic process to fabricate complex 3-D surfaces. To demonstrate their method, they constructed a nanofluidic chamber with a “staircase” geometry etched into the floor. The “steps” in this staircase—each level giving the device a progressively increasing depth from 10 nanometers (about 6,000 times smaller than the width of a human hair) at the top to 620 nanometers at the bottom—are what give the device its ability to manipulate nanoparticles by size in the same way a coin sorter separates nickels, dimes and quarters.
In these novel experiments, the researchers tested their device with two different solutions: one containing 100-nanometer-diameter polystyrene spheres and the other containing 20-micrometer (millionth of a meter)-length DNA molecules from a virus. In each experiment, the researchers injected the solution into the chamber’s deep end and then used electric fields to drive their sample across the device from deeper to shallower levels. Both the spheres and DNA strands were tagged with fluorescent dye so that their movements could be tracked with a microscope.
In the trials using rigid nanoparticles, size exclusion occurred when the region of the chamber where the channels were less than 100 nanometers in depth stayed free of the particles. In the viral DNA trials, the genetic material was coiled in the deeper channels and elongated when forced into the shallower ones. These results demonstrate the utility of the NIST-Cornell 3-D nanofluidic device to perform more complicated nanoscale operations.
Currently, the researchers are working to separate and measure mixtures of different-sized nanoparticles and investigate the behavior of DNA captured in a 3-D nanofluidic environment. For more information and images, see “NIST-Cornell Team Builds World’s First Nanofluidic Device with Complex 3-D Surfaces.”
* S.M. Stavis, E.A. Strychalski and M.Gaitan. Nanofluidic structures with complex three-dimensional surfaces. Nanotechnology Vol. 20, Issue 16 (online March 31, 2009; in print April 22, 2009).
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NIST Issues Open and Transparent Methods for Testing Electronic Voting Systems
The National Institute of Standards and Technology (NIST) has opened for public comment detailed new methods for testing future electronic voting systems’ compliance with voluntary federal standards. Touch screens, optical scanners and other kinds of electronic voting systems now appear at polls across the nation.
The new draft tests can be viewed at http://vote.nist.gov/voting-system-test-suites.htm.
The new tests will replace multiple proprietary laboratory testing techniques with a single transparent set of tests that will help give voters and governments confidence that the systems operate in a reliable fashion. Manufacturers also will have a better understanding of how their systems must perform to comply with federal standards.
“These new tests will ensure that everyone is on the same page for testing electronic voting systems,” says Lynne Rosenthal, manager of the NIST voting project. “This will not only benefit the general public and the government, but also they will help manufacturers build voting systems that meet federal standards.”
Under the Help America Vote Act of 2002, NIST assists the U.S. Election Assistance Commission (EAC) in developing voluntary standards for voting systems. In order to receive federal certification from the EAC, new voting systems must meet the Voluntary Voting System Guidelines (VVSG). The current version of the guidelines is known as VVSG 2005; the draft test suites apply to the VVSG Next Iteration (VVSG-NI), intended to address the next generation of voting systems. Ultimately, state or local governments determine whether their voting systems must meet federal standards.
The VVSG-NI calls for the testing of electronic voting systems using a prescribed set of test methods. The draft test suites—a series of documents, scripts and software programs—address various aspects of voting systems, such as hardware, usability and security. Each test suite lists the relevant VVSG requirement alongside a detailed method for testing compliance.
For example, in the hardware section, voting machines are required to operate properly in temperatures ranging from 5 degrees Celsius to 40° C (41 degrees Fahrenheit to 104° F) and relative humidity from 5 percent to 85 percent. While there are potentially many possible ways to test this, the draft standards specify a specific series of steps to be followed by every test lab, such as enclosing the voting system in a test chamber and checking for defects or malfunctions at specific temperature and humidity values in this range.
NIST requests public comments on the draft by July 1. Once the EAC finalizes the VVSG-NI, the test suites are expected to become required for testing future generations of electronic voting systems.
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TIP Competition Addresses Civil Infrastructure, Advanced Materials
The National Institute of Standards and Technology (NIST) has announced a 2009 competition for multiyear research funding in two major areas of national interest, civil infrastructure and advanced materials in manufacturing, under its Technology Innovation Program (TIP). TIP expects to provide cost-shared funding for approximately 25 new R&D projects.
Approximately $15 million in first-year funding is allocated for R&D projects in manufacturing that would enable better, more cost-effective use of advanced materials in innovative products. The competition is limited to technologies for nanomaterials; composites and superalloys, alloys; and smart materials, the three classes of materials considered most critical to potential growth areas for manufacturing. TIP is seeking proposals for new technologies for predictive modeling to enable improved material properties and better process design tools; and for improved methods to scale up advanced materials production from laboratory processes and to integrate advanced materials into products.
Approximately $10 million in first-year funding is allocated for projects addressing two specific needs in civil infrastructure. The first is a continuing need for innovative, cost-effective sensor and sensor-network technologies for non-destructive testing and monitoring of the structural health of major infrastructure components. This competition emphasizes technologies to detect corrosion, cracking, delamination and other structural damage in water resources systems such as water and wastewater pipelines, dams, levees and waterway locks, as well as bridges and roadways. The second focus is the need for new technologies for repair and retrofit and deals with how to do a better job repairing and upgrading existing structures. The emphasis is on practical technologies—including both novel materials and cost-effective methods for installing them—that would provide enhanced performance or longer service life than existing repair and retrofit materials and practices.
TIP promotes technological innovation by providing funding support to challenging, high-risk research projects that address critical national needs. The merit-based, competitive program can fund R&D projects by single small-sized or medium-sized businesses or by joint ventures that also may include institutions of higher education, nonprofit research organizations and national laboratories. TIP awards are limited to no more than $3 million total over three years for a single company project and no more than $9 million total over five years for a joint venture.
The due date for submission of proposals to the 2009 competition is 3 p.m. EDT, Tuesday, June 23, 2009. Proposals may be submitted electronically through Grants.gov (search for Catalog of Federal Domestic Assistance (CFDA) program 11-616 or Funding Opportunity Number 2009-TIP-01) or on paper to National Institute of Standards and Technology, Technology Innovation Program, 100 Bureau Drive, Stop 4701, Gaithersburg, MD 20899-4701. Review, selection and award processing is expected to be completed by the end of November 2009.
NIST will offer four public meetings for prospective TIP proposers and other interested parties to provide general information regarding TIP and the competition process, including eligibility and cost-sharing requirements, evaluation and award criteria, the selection process, and the general characteristics of a competitive TIP proposal. Proprietary technical discussions about specific project ideas will not be discussed.
The four TIP “Proposers’ Conferences will be held:
Additional sources of information on this competition include:
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NIST Launches YouTube Channel
As part of a U.S. government-wide effort to expand the amount of information available to the public about its programs, the National Institute of Standards and Technology (NIST) has created a channel on the video social networking site YouTube.
“This official YouTube channel is the first of several planned NIST Web sites hosted by the private sector,” says Gail Porter, director of NIST’s Public and Business Affairs office. “The effort is part of a broader, government-wide effort to encourage openness and transparency and to ’go to where the people are.’”
On the NIST YouTube channel, viewers can interact by sharing videos with their friends via email, posting links to the videos on their own Web pages, and writing comments below each video. About a dozen videos are now online, and additional videos are planned.
“We will be changing featured topics regularly,” says Porter, “to highlight work from across NIST. If you click on ‘Subscribe’ you can be notified through your YouTube account each time a new video is posted.”
The Department of Commerce negotiated a contract with Google that allows its agencies to establish YouTube channels. Other Commerce agencies such as the National Oceanic and Atmospheric Administration and the U.S. Census Bureau are also participating. Similar additional contracts are under negotiation with other social media sites.The new YouTube channel can be found at www.youtube.com/user/usnistgov.
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