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Applied Physics Division
INTRODUCTION
The Applied Physics Division (APD) has seven groups with a complement of 140 personnel, many of whom work on projects in multiple groups. These groups are Advanced Microwave Photonics, Faint Photonics, Quantum Nanophotonics, Fiber Sources and Applications, Magnetic Imaging, Sources and Detectors, and Quantitative Nanostructure Characterization. There appears to be an extensive cross interaction of personnel and resources between groups and excellent communications within the division.
Total annual funding is $22 million of which NIST base funding is 53 percent, decided centrally. Budgets allocated to groups range between $2 million and $ 4 million per year. The other sources are from NIST initiatives, including targeted funding such as laser welding, integrated photonics, and LIDAR; calibration services; and external funding sources, such as the Department of Defense (DoD), the Defense Advanced Research Projects Agency, the Advanced Research Projects Agency-Energy (ARPA-E), and Cooperative Research and Development Agreements (CRADAs) with universities and industry.
ASSESSMENT OF TECHNICAL PROGRAMS
Advanced Microwave Photonics
The activities of the program are summarized by the division as follows: “We research and develop technical approaches that address near- and medium-term resource bottlenecks in quantum information and quantum computing, specifically in the microwave frequency domain using superconducting circuits.”1
The Advanced Microwave Photonics Group (AMPG) consists of three NIST principal investigators, any one of whom could be a professor at a top-25 physics department. Also in the group are six associate scientists. Although relatively small in size, the AMPG investigates broad areas of superconducting quantum systems, perhaps indicating that “quantum microwave photonics” is a more natural designator. Given the impressive technical impact to date (e.g., pioneering optomechanical systems in the microwave regime and making seminal contributions to superconducting amplifiers), NIST may consider further augmenting the group with more staff scientists and/or technicians. In particular, there may be opportunities for this group to participate technically at a leadership level in helping develop and maintain standards of components for the emerging quantum information technology area.
Similar to other groups in the APD, the AMPG relies on NIST funding as well as external support, the latter predominantly from DoD. Notably, one research group is currently being partially supported by a Presidential Early Career Award, a testament to the group’s ability to attract top talent. In the long run, an additional outside funding source would give the group’s varied research interests more
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1 National Institute of Standards and Technology (NIST), “Applied Physics Division NRC Review,” presentation to the committee, May 1, 2018.
stability.
The AMPG uses state-of-the-art equipment to conduct its research, mostly purchased from companies (e.g., dilution refrigerators), although custom amplifiers and devices are designed and fabricated in-house.
Quantum Computing
The AMPG has extensive expertise in superconducting devices and systems—of direct relevance to superconducting quantum computing. Quantum computation relies on fast and high-fidelity coupling between quantum information-holding systems, that is, qubits. The most successful two-qubit gates today rely on direct, resonant, or dispersive coupling between two qubits; the nature of this coupling is such that only two qubits can be coupled at a time, and it is very difficult to turn off coupling in the qubit’s idle state.
Accomplishments
AMPG scientists have been leaders in developing parametric-based gates. Parametric-based strategies for qubit gates have percolated through the superconducting qubit community over the past few years; they offer opportunities to improve scaling of many-qubit systems, such as reducing wire count and reducing the need for microwave passives (hardware volume in the cryostat), while increasing connectivity and gate speed. The AMPG has developed a parametric-based architecture that dramatically increases the connectivity between qubits in a superconducting qubit system and reduces wire counts by almost a factor of four.
Opportunities and Challenges
AMPG scientists are well connected with the quantum computing community, so dissemination of their ideas is not difficult. There has been a lack of publications in this area over the past couple years. Validation of the group’s concepts experimentally, or even the dissemination of theoretical manuscripts describing their proposals, would benefit the community and the group.
Optomechanics
AMPG scientists are pioneers of the relatively new field of optomechanics in the microwave regime. They are the inventors of a novel “drum-based” approach to mechanical motion-microwave photon coupling, with dramatically increased coupling strengths beyond the state of the art. Utilizing mechanical motion strongly coupled to photons offers the ability to both demonstrate fundamental quantum measurement concepts in well-controlled systems and provides opportunities for new devices. In particular, mechanical systems offer an excellent means to transduce information between energy regimes of relevance to many fields.
Accomplishments
The AMPG has demonstrated efficient nonreciprocity in a microwave optomechanical circuit. The group has also performed significant work on mechanically mediated microwave frequency conversion in the quantum regime.
Opportunities and Challenges
The optomechanics activities of the AMPG are well integrated within the group and with JILA; this synergy could reveal further opportunities for progress in work on optomechanics.
Amplification and Measurement
The AMPG uses coupled-mode theory to understand nonreciprocity and to synthesize directional parametric amplification. Parametric multimode theory promises a new class of directional parametric amplifiers, signal routers, programmable filters, and even creation of synthetic gauge fields—of interest for exploration of new quantum systems.
Accomplishments
The AMPG has created novel and useful superconducting amplifiers and nonreciprocal systems. The group has developed a novel graph-theoretic approach to designing and understanding driven amplifier (and related) systems, which they applied to develop new and useful microwave components, which is relevant to quantum computing and measurement science. In a sense, these amplification and measurement efforts attempt to unify the disparate quantum technologies across AMPG under a single conceptual umbrella. The AMPG investigators are leaders in superconducting amplifier development.
Opportunities and Challenges
AMPG’s scientists have taken steps to apply their technology to standards—both for traditional research thrusts and for the nascent quantum information science and technology industry. The field could use an expert body to qualify and develop standards for cryogenic, superconducting, and microwave components. These standards are generally and widely needed across the community. The AMPG could take a leading role in this space, but it would require resources for the needed staff technicians, along with relevant equipment.
Faint Photonics Group and Quantum Nanophotonics Group
The activities the Faint Photonics Group (FPG) and Quantum Nanophotonics Group (QNG) are summarized as follows: “We are developing the best metrology at faint light levels. We provide and use optical single-photon sources, detectors to solve challenging research, industrial, and governmental problems when applicable.”2
Superconducting Detectors
The FPG develops two types of single-photon detectors; both are based on the fragility of the superconducting state close to its transition.
The high-efficiency (70 to 95 percent) superconducting nanowire single-photon detectors (SNSPDs) from ultraviolet to mid-infrared are currently the fastest single-photon detectors for counting photons. Unlike most groups, who use niobium-nitride superconducting meander structures,3 the FPG is
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2 NIST, “Applied Physics Division NRC Review,” presentation to the committee, May 1, 2018.
3 The meander structure is a geometrical configuration of the detector in which the conductors are folded back and forth to make the overall length of detector shorter than the original length of straight wire.
using amorphous tungsten silicide (WSi), which offers better homogeneity and therefore less possibility for weak spots.
The high-efficiency (~98 percent) transition edge sensors (TESs) for 1550 nm are made of superconducting tungsten. The current version of these detectors was initially developed at NIST and is a widely used method for cryogenic particle detectors. It is evident that the FPG is a world leader in the development and use of both detectors.
Accomplishments
Noteworthy FPG accomplishments in superconducting detectors include the following:
- Increasing the efficiency of the SNSPD by using amorphous WSi.
- Developing the fastest detector for single photon counting (< 100 picoseconds) while working at approximately 5 K, which is easily obtained with, for example, closed-cycle refrigeration.
- Using its SNSPD in the first (one of three) Loophole-free Bell inequality experiments with photons.
- Providing its TES detectors to the Zeilinger group for their Loophole-free Bell inequality experiments with photons.
- Demonstrating a high-efficiency SNSPD at a wavelength of 315 nm and an operating temperature of 3.2 K, with a background count rate below 1 count per second at saturated detection efficiency.4
Opportunities and Challenges
FPG’s opportunities are primarily in the use of its detector capabilities in exploratory projects (with the QNG), such as three-dimensional (3D) fluorescence imaging with entangled photons, in the area of quantum biometrology, and use of Bell inequality experiment as a random-number generator.
Nanophotonic Devices to Enable Optoelectronic Measurements
The QNG uses one chamber of a double-molecular-beam epitaxy (MBE) system for growth of gallium-arsenide (GaAs)-based MBE structures (the second chamber is used by the Quantitative Nanostructure Characterization Group for gallium-nitride (GaN)-based structures). The following projects associated with this facility:
- Semiconductor saturable absorber mirrors (SESAMs),
- GaAs:Er for ultrafast carrier recombination (terahertz generation, photoconductive switches),
- InAs quantum dots for single-photon sources and transduction,
- Vertical (external) cavity surface-emitting lasers (NIST-on-a-Chip), and
- GaAs/AlGaAs heterostructures for chip-scale nonlinear optics.
Accomplishments
Obviously, the QNG group is not an MBE-centered group, but rather uses the MBE to fabricate structures that are needed for its projects. It seems to be achieving high-quality growth, which will allow it to integrate the semiconductor-based sources with its experiments. It develops and produces novel devices such as sources and saturable absorber mirrors. An example is the ultra-low-noise, monolithic,
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4 D.H. Slichter, V.B. Verma, D. Leibfried, R.P. Mirin, S.W. Nam, and D.J. Wineland, 2017, UV-sensitive superconducting nanowire single photon detectors for integration in an ion trap, Opt. Express 25:8705-8720.
mode-locked solid-state laser. The group has a fabrication facility that enables development of state-of-the-art structures.
Opportunities and Challenges
The MBE facility and its projects are well integrated into the research of the APD, and so this synergistic collaboration may yield future applications of the group’s device development efforts.
Integrated Optics, Quantum Optics, and Quantum Biometrology
The QNG develops nanophotonic devices to enable optoelectronic measurements in a wide range of wavelengths. Guided by fundamental physics measurements, or by technological challenges, the group works on a wide range of projects.
Accomplishments
A notable integrated optics experiment, which utilized the single-photon detectors produced by FPG and single-photon sources produced by QNG, is the Loophole-free Bell Inequality experiment.
Supporting another thrust on neuromorphic computing, the group developed multiplanar amorphous-Si waveguides exhibiting low-loss crossings, low crosstalk, and efficient interplanar coupling.
A new direction is in microscopy, involving entangled photons. Entangled photons significantly improve ordinary optical techniques, particularly in enhanced microscopy. PML and the NIST Materials Measurement Laboratory (MML) joined efforts to develop entangled photon microscopy capabilities, directed toward biomedical applications. The main advantage of the technique is the ability to use low power, which will minimize biologic cell damage.
Opportunities and Challenges
The present project concentrates on 3D fluorescence imaging with entangled photons. Other biomedical applications will be enabled with the successful demonstration of this capability.
Non-Conventional Superconducting Electronics
The FPG integrates the single-photon detectors into superconducting structures for a variety of applications. In collaboration with JILA, it also develops optical/microwave hybrid quantum systems.
Accomplishments
The group has integrated silicon nitride waveguides with evanescently coupled ring resonator filters of SNSPDs to couple specific colors to the SNSPDs.
Fiber Sources and Applications
The Fiber Sources and Applications Group currently performs four projects: fiber-optic based combs, dual-comb spectroscopy, time-frequency transfer, and laser ranging. Personnel include approximately eight full-time equivalent staff (FTEs) with nine associates. The group leader is also presently serving as interim division director. More than half of this group’s $4 million budget is external in the form of significant DoD funding, along with CRADAs and support from the U.S. Department of Energy.
Accomplishments
The work of the Fiber Sources and Applications Group is primarily based on the scientific understanding, development, and application of fiber-based frequency combs; in this field, the group is world-renowned for its contributions and leadership. One notable and important application is dual-comb spectroscopy that is broadband and requires no moving parts. The technology is based on telecommunications wavelengths and components. Initial demonstrations show that these combs can be used for remote optical sensing of greenhouse gases or hazardous gases with highly accurate spatial resolution and ranging information.
The group has developed a free-space, open-path testbed on the NIST campus and a longer-range path over the city of Boulder, Colorado. These systems have been operated for periods of multiple weeks with accuracies for quantification of CO2 and CH4 concentrations that are 10 to 100 times better than other open-path systems. A demonstration of an open-path measurement using a drone as an airborne reflector showed collection of greenhouse gas data at arbitrary distances and altitudes. Further trials at longer distances and remote sites are under way.
Another important application of these fiber-based frequency combs is for time and frequency transfer (i.e., dissemination) for multiple potential applications, including highly accurate position, navigation, and timing. In particular, coarse and fine two-way timing can be obtained by employing a redefinition of the “second” as precisely placed optical pulses in a comb-based synchronization system. A pair of clocks has been synchronized in this manner via the flight path of an airborne retroreflector on a quadcopter.
The level of external interest in this work is impressive, as evidenced by the significant level of external financial support. In addition, the breadth of the work—from concept to field-test—is also impressive.
Challenges and Opportunities
There are major challenges inherent in the mission of this group, but these are primarily of a technical nature that the group is well-equipped to attack, including enhancing the amplitude uniformity and output power of the comb lines and increasing the coherency and reducing the noise. The group is successful at choosing, addressing, and solving problems that are of interest to others in the commercial and governmental world. Laudably, the group intends to continually push the state of the art of their technology and applications.
The group has used drones with retroreflective mirrors for signal return in order to do vertical sampling of the air. While the concept is an opportunity for environmental monitoring, the use of drones entails potentially undesirable consequences. Consideration might be given to helium-filled balloons equipped with global positioning system (GPS) and gas jets for positioning and station keeping.
Magnetic Imaging
The Magnetic Imaging Group, a research and service group, serves the global need for calibration standards—ensuring that imaging instruments perform to specifications, making commercially available calibration standards (phantoms) for human magnetic resonance imaging systems, and calibrating or measuring the relaxation parameters of proposed magnetic resonance imaging (MRI) contrast agents. The group also has embarked on micro-fabricated contrast agents for MRI, ultralow-field MRI, and neuromorphic computing.
The principal scientific personnel consist of three career scientists, four term scientists, and two affiliates. The annual budget is $2.51 million, with 81 percent NIST-base funding and 19 percent split between non-base NIST and external contracts.
NIST has an in-house variable field nonclinical scanner and access to other clinical scanners in the Boulder and Denver area, including clinical commercial MRI systems and a small-bore 14 Tesla nuclear magnetic resonance (NMR) system at the University of Colorado. The group is installing a very-low-field, portable MRI system with 100 milliTesla capability to enable agricultural optimization studies of feed grasses.
Major improvements in space available to this group have occurred in the past 3 years with the opening of a new building and renovations of laboratory spaces needed for the specific goals of this and other groups (e.g., clean rooms).
Accomplishments
Physical Phantoms
Phantoms for breast imaging, conventional, and diffusion-weighted brain-imaging MRI have been fabricated and to some extent commercialized. These were developed in collaboration with the major MRI society, the Radiological Society of North America (RSNA), and the National Cancer Institute and the University of California, San Francisco, Medical Center.
The MRI Standards project develops “phantoms” (i.e., calibration structures) and validates quantitative imaging protocols. Its area of emphasis is on standards for cancer, brain, and multimodal imaging.
This work of the Magnetic Imaging Group is of global importance because the phantoms allow calibration and standardization work, which is vital to population studies and multicenter trials of proposed medical therapies where imaging endpoints are needed.
New work is under way on a phantom that would provide evaluation of diffusion-weighted imaging and nerve bundle tractography, where algorithm optimization is a major issue in neuroimaging of brain circuit connectivity.
The group envisages that future directions may focus on multimodal imaging, such as combine information from two or more imaging modalities—MRI, computed tomography (CT), positron emission tomography (PET), or ultrasound (US). These combined techniques, such as PET-Magnetic Resonance (PET-MR) or MR-US, necessitate the development of quantitative imaging protocols. These projects develop the calibration structures and quantitative imaging protocols with collaborators from academic institutions, professional societies (International Society of Magnetic Resonance in Medicine [ISMRM], RSNA), and where applicable, other federal agencies.
Biomarker Calibration Service
An excellent example of the sophistication and elegance of the NIST culture in calibration and standards is the service for calibration of contrast-agent proton-spin relaxation times,5 which describes the calibration service as providing T1 and T2 relaxation times of materials used in phantoms in order to verify the accuracy of quantitative MRI measurements. The measurements are made at fields of 1.5, 3.0, and 7 Tesla and temperatures between 0 and 50°C, as specified by the customer. A unique aspect of NIST calibration is the careful attention to precise temperature control, because the community has not yet recognized that there is a 2 percent change per degree C in both T1 and T2 relaxation times.
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5 M.A. Boss, A.M. Dienstfrey et al., 2018, Magnetic Resonance Imaging Biomarker Calibration Service: Proton Spin Relaxation Times, NIST Special Publication 250-97, U.S. Department of Commerce. Gaithersburg, Md., May.
Neuromorphic Computational and Simulation Systems
Three groups in the APD are engaged in development of systems that measure attributes of the human central nervous system. To understand how the human brain works, experiments investigate brain function and dysfunction. Neural systems that can operate 10 billion times faster than biological systems are intended to measure spatial and temporal correlations in high-density networks to understand memory and data processing.
This project utilizes superconducting single flux quantum (SFQ) and spintronics devices. The Magnetic Imaging Group has developed a stochastic model of magnetic Josephson junctions suitable for high-density neural simulations. The circuits allow most, if not all, known neurophysiology functions, including inhibition.
Ultra-Low Magnetic Field Instrumentation
Ultra-low field (0.1 milliTesla) scanners can serve major biomedical applications as well as for materials characterization. New magnetic imaging modalities are being developed, including magnetic particle imaging (MPI), electron paramagnetic resonance (EPR)-enhanced MRI, and micro-fabricated sensors and contrast agents visible in an MRI.6 For example, the Magnetic Imaging Group is developing a plant root/soil imaging system that is expected to allow studies of the effect of climate, irrigation, fertilizer, and so on, on plant growth. The goal is to provide an image of roots in an intact soil column, using MRI with a very low magnetic field in order to avoid the magnetic susceptibility heterogeneity between plant tissues and various components of soils. These susceptibility differences lead to magnetic resonance signal-phase differences with the creation of large artifacts. The project is run by Texas Agricultural and Mechanical University (TAMU), and the instrumentation is led by a researcher at Harvard University. NIST is developing appropriate phantoms for the project, as well as doing some in-lab studies to advise some of the in-field work. The funding proposal to ARPA-E was $10 million; $4 million was made available. The goal now is to produce 15 MRI systems that can be implanted in the soil. The current instrument is copied after the Boston system and serves as a testbed to show any influences of the instrument on normal plant growth. The prototype is nearly ready for experiments.
The project is supported by ARPA-E and a collaboration with TAMU, with partners at the Athinoula A. Martinos Center for Biomedical Imaging in Charlestown, Massachusetts, and ABQMR, Inc., in Albuquerque, New Mexico.
Innovations in MRI In Vivo Sensors of Tissue Physiology
Work on MRI injectable “smart” agents is aimed at developing new micro- and nanoparticle-based contrast agents for magnetic resonance imaging and sensing schemes. The major benefit is that these sensors, plus MRI detection, do not suffer from attenuation of light photons and limitations of ionizing radiation; however, they do have the limitations of sensitivity inherent in magnetic resonance imaging and spectroscopy. The new agents include synthetic antiferromagnet nanoparticles. The high-moment iron microparticles provide enhanced T2* contrast for in vivo cell tracking. The radio-frequency-addressable sensor assemblies comprise pairs of magnetic disks with interstitial, swellable hydrogel material; these are able to reversibly reconfigure in rapid response to select stimuli and provide dynamic NMR spectral signatures that are geometry dependent. The sensors can be fabricated from biocompatible materials and are themselves detectable at low concentrations.7 Applications include remote sensing of biological tissue mechanical stresses in human physiology research.
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6 Adapted from NIST, “Advanced Magnetic Imaging Methods,” https://www.nist.gov/programs-projects/advanced-magnetic-imaging-methods, accessed October 1, 2018.
7 G. Zabow, S.J. Dodd, and A.P. Koretsky, 2015, Shape-changing magnetic assemblies as high-sensitivity NMR-readable nanoprobes, Nature 520:73-77.
Challenges and Opportunities
The Magnetic Resonance Group provides a vital service to the magnetic resonance clinical and research communities. Not only does this work on standards address the wide variations in MRI equipment performance from manufacturer to manufacturer, but from clinic to clinic and even day to day for the same manufacturer. The phantom systems allow not only physical system calibration but also allow evaluation of slight differences in pulse sequences, including radio frequency and gradient protocols so that algorithms may be optimized.
In addition to service, the group has launched projects where a national need is perceived and has taken on the challenge of investigating how its talents can provide solutions. Collaborations both within the division and outside NIST exist for every one of the seven groups (e.g. neuromorphic systems, imaging plant growth).
While instrumentation and space resources are excellent for most of the groups, the Magnetic Resonance Group is badly in need of a clinical-class MRI so that appropriate phantom design, as well as initial testing, can be readily accomplished without going to other sites. NIST has access to nearby clinical commercial MRI systems, but nonetheless might evaluate whether a clinical system of its own would improve productivity by eliminating wait times, provide opportunities for CRADAs and other partnerships that offset costs, and decrease costs that would otherwise occur using other clinical scanners in the area.
Productivity of the investigators is great in spite of sparse evidence of administrative support (e.g., no human resources staff in Boulder).
Sources and Detectors
The Sources and Detectors Group is an excellent example of the value that NIST brings to the scientific and industrial communities. The group uses its expertise to significantly advance the science of measuring light; it makes prototypes, such as detectors, for measuring light pressure from laser sources. In doing so, NIST reduces fundamental advances to practical instruments, and it provides essential service to outside entities in calibrating optical technologies that cannot be calibrated elsewhere with the required accuracy. From a technical standpoint, the group has made excellent advances, identified key challenges, and is planning for future approaches. The funding for this group is $4.11 million, with 11 percent from calibration for outside entities on a cost-neutral basis, making it highly valuable to external stakeholders in the true spirit of NIST. The group’s expertise and personnel are highly qualified and productive.
Accomplishments
Examples of Sources and Detectors Group accomplishments include the following:
- The group’s goal of advancing the science of accurately measuring optical power from very high to very low powers over wide wavelength ranges is laudable. This vision makes their current excellent advances applicable to an extremely wide variety of commercially significant applications. Their scope includes all properties of light, including phase, polarization, and spatial distribution.
- Measurements of mass tend to have errors that compound as the mass size is reduced. The group’s approach is to break this condition when measuring optical power, such that measuring extremely low power will be accomplished by comparisons to single photons rather than by tracing back to the larger powers. This new approach makes the measurement errors more independent of power level. The science and impact of this work are highly significant.
- The group’s advances in miniaturization of radiometry equipment are innovative. It has reduced the size and weight of many types of optical measurement equipment, with an increase in robustness and reduction in cost. This opens up many new avenues of deployment for optical metrology in the field, where it is most needed. One example is to place radiometry devices on small satellites. It has taken seriously the vision of NIST-on-a-Chip.
- Metrology science could benefit greatly by their work in tracing optical power back to the kilowatt. This can holistically tie together multiple different metrology subfields under a single paradigm.
Challenges and Opportunities
The group’s equipment and facilities are outstanding, provide capabilities that are among the best in the world, and merit support at a high level so that it can remain a world leader.
It has hosted various impressive workshops in order to disseminate ideas, facilitate collaborations, and make available its capabilities and expertise.
Quantitative Nanostructure Characterization
The Quantitative Nanostructure Characterization Group currently performs four projects: atomic scale characterization, quantitative precision imaging facility (PIF), nanoelectromagnetics, and nanostructure synthesis. Personnel include seven FTEs, two post-doctoral researchers, and one graduate student. The annual budget is $3.15 million, with 71 percent NIST base and 12 percent from service. A significant infrastructure for the group includes a cluster of four ion- and electron-beam imaging tools, near-field scanning microwave microscopy, and GaN MBE growth capability. The group is developing new atom probe tomography tools.
Accomplishments
The Quantitative Nanostructure Characterization Group has modified commercial instrumentation to obtain broadband microwave reflection and transmission measurements in the frequency range 1 to 17 GHz. This instrumentation has been used for sensitive defect localization in two-dimensional (2D) materials. In addition, the group has investigated carrier dynamics in 2D tellurene under electrically biased operation.
The group has assembled a sophisticated tool set cluster for ion- and electron-beam analysis of materials and structures. These tools are usually commercial instruments that have been modified by NIST investigators to make them at or ahead of the state of the art. NIST investigators have also used the cluster tools for projects that serve the twin purposes of proving the limits of the tools and of making original contributions to the art. Two excellent examples include transmission electron microscopy-based analysis of crystal phases at interfaces in rhenium– gold (Re+Au) superconducting films, and selective-area growth of GaN nanowires by MBE. Studies of the regrowth interface of these nanowires, grown in the NIST MBE chamber, yielded information on polarity differences in hexagonal GaN. The NIST LED nanowire device results have shown the need to consider these post-processing regrowth interfaces.
The group is extending atom probe tomography to include laser-assisted tomography and extreme atom probe tomography. Laser assistance has been used to trigger field evaporation and has been used in collaboration with the University of California, San Diego, to reveal Si incorporation in Hf-doped ZnO multilayers. The group is developing extreme atom probe tomography to eliminate the conventional laser and move to the extreme ultraviolet (EUV) regime, adding in situ transmission electron microscope
analysis. This work has the potential to significantly advance the practical utility of atom probe tomography.
The technical programs in this group are strong and reflect development of sophisticated characterization tools that are among the best in the world. Although its mission is primarily development of these tools, its research contributions using these tools are strong and include a mix of collaborative research and unique NIST-based research.
The expertise within the group is diverse. The group’s personnel have strong interactions with other scientists in the division and some effective collaborations outside NIST. The group’s facilities, equipment, and human resources are adequate and balanced with respect to instrumentation development. Its research programs seem to be well coupled to stakeholder needs.
Challenges and Opportunities
There are two major challenges inherent in the mission of this group. The first is to continually push the state of the art of their unique characterization tools and processes in order to remain a world leader. At the same time, it is important to make the most of these capabilities while at the leading edge. There is, of course, tension between these challenges, because upgrading equipment often takes it out of service. Additionally, while there is significant collaboration, it could be increased. The group may benefit from broader collaborations on different materials systems, particularly with the atom probe tomography development. Validation and then commercial transfer of atom probe tomography could be accelerated.
As a potential provider of unique characterization, it is incumbent on the group to broadly articulate its expertise. The group participates in the normal avenues for dissemination—papers, patents, and presentations—and has a significant investment in workshops held locally.
PORTFOLIO OF SCIENTIFIC EXPERTISE
Overall, the review panel found APD’s accomplishments and current leadership outstanding, as evidenced by the groups’ activities and contributions. This progress is particularly noteworthy in view of the major changes in leadership and administrative posts since September 2017.
The visit left the panel with the clear impression that APD’s principal investigators are competent scientists engaged strongly with external partners and with one another working at the forefront of their fields. The division has an impressive list of former alumni, some of whom are now leading principal investigators.
ADEQUACY OF FACILITIES, EQUIPMENT, AND HUMAN RESOURCES
APD’s personnel resources have experienced major changes occasioned by the loss of 7 persons (of a total of 17) from leadership and administrative personnel since September 2017, including the division leader and one of the group leaders. Replacements in four areas have occurred with acting appointments, including the division leader, who has kept the division on a steady and progressive path of continuing high performance. An overall administrative concern in Boulder is the apparent absence of an onsite human resource support office and personnel.
DISSEMINATION OF OUTPUTS
Dissemination of APD outputs is through publications, conference presentations, interactions with other federal agencies (e.g., DARPA, DoD, Intelligence Advanced Research Projects Activity, and
ARPA-E), contracts with industry and university, and provision of measurement services (e.g., calibrations and standard reference data and materials).
Collaboration with universities and industry, as well as CRADAs and patents, are additional modes of dissemination. Other forms of dissemination are workshops, symposia, visiting science and engineering personnel, and the fact that many postdoctoral researchers and affiliates leave NIST to join industry and universities, as well as other government research organizations.
Information on involvement in the scientific community through leadership roles, recognition through awards, invited presentations, and international activities was not completely available at the time of this assessment, but members of this division had received national recognition for innovations. As part of the dissemination portfolio, an enhanced division-wide culture that values increased involvement in external professional activities, such as conference organization, journal editorships, and professional society governance, would lead to greater visibility for the investigators and NIST in general. These also lead to society fellowships, research awards, and other forms of recognition.
Accomplishments
The scientists in APD have placed highly cited publications in refereed journals, including two with over 400 citations in 2015;8,9 one with over 300 in 2014;10 and one with over 700 in 2013,11 to pick just a few examples. More recent publications will likely accumulate comparable numbers of citations.
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8 L.K. Shalm, E. Meyer-Scott, B.G. Christensen, P. Bierhorst, M.A. Wayne, M.J. Stevens, T. Gerrits, et al., 2015, Strong loophole-free test of local realism, Phys. Rev. Lett. 115:250402.
9 M. Giustina, M.A.M. Versteegh, S. Wengerowsky, J. Handsteiner, A. Hochrainer, K. Phelan, F. Steinlechner, et al., 2015, Significant-loophole-free test of Bell’s Theorem with entangled photons, Phys. Rev. Lett. 115:250401.
10 R.W. Andrews, R.W. Peterson, T.P. Purdy, K. Cicak, R.W. Simmonds, C.A. Regal, and K.W. Lehnert, 2014, Bidirectional and efficient conversion between microwave and optical light, Nature Physics 10:321.
11 F. Marsili, V.B. Verma, J. A. Stern, S. Harrington, A. E. Lita, T. Gerrits, I. Vayshenker, B. Baek, M. D. Shaw, R. P. Mirin, and S.W. Nam, 2013, Detecting single infrared photons with 93% system efficiency, Nature Photonics 7:210.
