INTRODUCTION
The Quantum Measurement Division (QMD) goals and strategic plans are mostly driven by the redefinition of the international system of units (SI), specifically by introducing the quantum SI with a completion target of 2018. This includes redefinitions of the kilogram, ampere, volt, kelvin, and mole. The quantum SI is an approach to implementing the International Committee for Weights and Measures (CIPM) recommendation 1 (CI-205). As a result, this division covers an extraordinary range of activities in fundamental and applied studies. Fundamental work includes research on single atoms and photons, quantum degenerate atomic gases of bosons and fermions, cavity optomechanics, and quantum optics. Spectroscopic work, with its long and distinguished history, includes the atomic spectroscopy database, and metrology covers aspects that include fundamental measurements of mass and force; basic electrical measurements of voltage, ampere, and resistance; and time-synchronized measurements for smart grid applications.
In its plans to physically realize the electrical, mass, and force units, the division focuses on the Committee on Data for Science and Technology (CODATA) recommended values of the fundamental constants of physics and chemistry. With the increasing reliance on quantum-based measurements, the division explores foundational questions directed toward advances in all units, including measurement schemes beyond the standard quantum limit. Another focus is the dissemination of the primary realizations at NIST, illustrated by the mise en pratique efforts to introduce a new realization of mass measurement based on electromagnetic levitation.
ASSESSMENT OF TECHNICAL PROGRAMS
Atomic Data and Spectroscopy
The Atomic Spectroscopy Group has an extraordinary record of accomplishments over its multidecade history. Calendar years 2013 and 2014 are typical, with 32 and 25 refereed publications respectively.
The expansion of astronomical spectroscopy into new wavelength ranges is a great opportunity for the group. Mercury cadmium telluride (HgCdTe) detector arrays have opened the infrared (IR), and various orbiting facilities have opened the ultraviolet (UV), vacuum ultraviolet (VUV), and x-ray spectra. Knowledge of the detailed physics and chemistry of the remote universe is gained from spectroscopy. The era of exoplanet studies has started, and the era of exobiology will soon follow.
Although quantum information (QI) processing in the form of a device for factoring large numbers is a major goal of QI research, other applications of QI devices may have commercial significance much sooner (for example, quantum key distribution schemes and early-stage quantum computing products).
Experimental Solid State Quantum Information
Within the field of experimental, solid state QI, a competition is under way between trapped-atom/ion systems and solid-state (SS) systems for QI processing. Trapped-atom/ion systems offer the promise of long coherence times, but SS systems promise greater scalability. This PML group investigating experimental solid-state QI is developing an original and promising concept for a SS system for QI processing, using electromagnetic separation. Isotopic separation efforts in the group could be expanded with a modest investment. Such an expansion would have implications for metrology, e.g., improvements in Avogadro’s number, and for technologies such as QI.
Experimental Cold Atoms, Quantum Optics, Nanomechanical Science, and Theory
This is a core enabling component of the PML that provides science drivers and is a powerful innovation engine. It also complements the work of the Quantum Physics Division, located in Boulder, and fits well into PML’s NIST-on-a-Chip activities.
As quantum materials become increasingly important, a central goal of this work is to help shed light on these materials by designing and realizing many-body Hamiltonians in ultracold atoms, where exquisite control is available. Another motivation for the work is to investigate the use of quantum many-body systems to make new kinds of measurements. These groups are doing experimental and theoretical research on ultracold atoms, quantum optics, and nanomechanics that is among the best in the world. The researchers produce large amounts of outstanding science and enjoy international recognition. The expertise of the experimentalists covers a broad range of areas, including quantum optics and ultracold atomic physics.
The experimental studies of many-body effects in ultracold atomic systems are among the best in the world, and the recent test of Bell inequalities, eliminating the remaining loopholes of previous experiments, is a telling example of the synergy between different areas of expertise at Gaithersburg and JILA, the extraordinarily successful joint institute of the University of Colorado, Boulder, and NIST.
In the relatively new area of optomechanics, a promising direction is the development of new bridges between quantum physics and sensor development, with promising applications of optomechanics to thermometry. There are also possible applications of single-photon sensing in biological systems.
The theoretical efforts also cover a remarkable range of topics, including many-body physics, quantum optics, traditional atomic physics and collision physics, and QI science. The theorists play an important role in building bridges between different activities, including between other divisions within NIST.
Techniques developed by the PML for precisely placing dopants in silicon may be applicable in more general semiconductor fabrication.
The partial relocation of the groups working in this area to the University of Maryland campus presents both opportunities and challenges. Opportunities include more access to students, the possibility of PML staff seeking funding as University of Maryland adjunct faculty, and additional outreach and education through teaching. At the same time, this geographical separation raises the challenge of maintaining close collaboration and communication with the Gaithersburg NIST campus.
Fundamental Electrical Measurements, Applied Electrical Metrology, Mass and Force, and Synchrometrology
The incremental improvements in the key electrical measurements triangle (voltage, current, and resistance) are demonstrating continued PML leadership in attempting to increase accuracy while reducing uncertainties. The venturing into new materials and the associated quantum phenomena, such as the use of graphene for resistance and the Josephson effect for voltage measurements, is focusing on
breakthrough approaches as they become available through new technological developments and improved theoretical understanding.
Further refinement of the CODATA constants is critical for continued efforts of the fundamental electrical measurements, applied electrical metrology, and mass and force work.
The Applied Electrical Metrology Group is maintaining responsibility for well-established AC-DC measurements and is also exploring the AC-DC metrology of the future. A relatively new activity that is primarily focused on smart grids addresses issues of synchrophasor measurements, new sensors, and the associated problems of interoperability and cybersecurity.
In the mass and force research area the general direction of using quantum physics to devise a substitute for artifacts (the watt balance and mise en pratique) is a very promising and much needed approach to reducing the cost and increasing the dissemination of calibration references for mass and force. This is an impressive collaboration between two formerly independent groups that merged into the division. The potential to make key contributions to the next SI revision is significant and remains an important focus for NIST. The key challenge may be to achieve the right balance in staffing the various efforts, particularly those with a long history of contributions versus emerging ones.
The PML areas of involvement in the smart grid areas are recognized by industry and users as needing some breakthroughs to serve the potentially huge domain of future commerce (estimated by the Electric Power Research Institute [EPRI/] at almost $500 billion). NIST visibility could be increased by engaging various groups in this area beyond those involved in the Smart Grid Interoperability Panel (SGIP). The choice of where to concentrate and focus already limited resources remains an issue.
The PML could also focus on smart grid sensors other than phasor measurement units (PMUs), with a goal of identifying how to help industry obtain more precise, synchronized, and reliable measurements. In particular, measurements under dynamically changing conditions are widely untapped in the smart grid standardization area, and the PML has an opportunity to position itself as a worldwide leader if it tackles this difficult problem. Development of metrology for assessing effectiveness of standards for the grid cybersecurity and privacy remains a huge challenge.
The ability of the PML to maintain its leading position in what is one of the oldest metrology areas is an accomplishment.
PORTFOLIO OF SCIENTIFIC EXPERTISE
Through its highly productive scientific exchange, with over 150 journal papers published in 2014, numerous awards received in the last 5 years, and the hosting of over 90 guest researchers while maintaining its own staff of 75, the division remains an essential focal point of the world efforts on physical measurement sciences.
ADEQUACY OF FACILITIES, EQUIPMENT, AND HUMAN RESOURCES
Atomic Data and Spectroscopy
The Atomic Spectroscopy Group has unique facilities, including a 2 m normal-incidence spectrometer, a vacuum ultraviolet (VUV) spectrometer, grazing-incidence spectrometer, and tunable single-frequency lasers. Some of the instruments—for example, the research-grade Fourier transform spectrometer (FTS)—are unique in this hemisphere. The shortage of technicians to maintain and upgrade the instruments is very serious, even though the FTS and the data center are staffed by excellent scientific experts.
The Atomic Spectroscopy Group’s scientific expertise is in urgent need of strengthening due to the loss of both electron beam ion trap (EBIT) expertise and expertise on highly ionized atoms (HIAs).
The departure and retirement of key atomic spectroscopy staff presents an opportunity to renew the staff and to take the group in new directions.
Experimental Solid State Quantum Information
The group has a combination of high-level theoretical and experimental expertise. The preparation of isotopically pure silicon films using electromagnetic separation is essential to implementation of the SS QI concepts under development by the PML. The productivity of the present electromagnetic (for example, mass spectrometer) separation system could be increased with a modest investment. The group is providing films for other QI research groups.
Experimental Cold Atoms, Quantum Optics, Nanomechanical Science, and Theory
The human resources are excellent, with a number of outstanding recent hires. Following the move to the Joint Quantum Institute (JQI) on the University of Maryland campus, many staff researchers are moving to groups that are more university-like, with three or four graduate students and one or two postdoctoral researchers, instead of relying more heavily on postdoctoral researchers. One advantage is that there is perhaps less pressure to produce fast results with students, who, in contrast to postdoctoral researchers, are under less pressure to accumulate a portfolio of results within a couple of years and may focus more on challenging long-term projects.
A substantial fraction of the activities of this group has been relocated to, or is in the process of moving to, the JQI. The new Joint Center for Quantum Information and Computer Science (QuICS), also located on the University of Maryland campus, is also a joint venture with the NIST Information Technology Laboratory (ITL); this further strengthens intra-NIST collaboration as well as collaboration with the University of Maryland.
Opportunities associated with the move to the JQI and the QuICS on the University of Maryland campus include the benefits of interactions with university faculty, researchers, and students; the possibility of attracting more students to NIST projects; and the opening of new funding avenues. There are also opportunities to disseminate results through teaching.
Fundamental Electrical Measurements, Applied Electrical Metrology, Mass and Force
NIST’s ability to maintain high-quality facilities using limited human resources and a relatively limited budget is quite impressive. An example of the PML’s ability to maintain its complex facilities is the effort that identified issues with the 4.45 MN force standard machine and helped to expedite its reconditioning. The machine was built several decades ago, and the PML group performed precise modeling of the deterioration phenomena associated with the material galling that developed in key structural components within the stainless steel weight stack.
In the Fundamental Electrical Measurements Group and Applied Electrical Metrology Group, some of the efforts are covered by one or two people only, so staffing may have to be reassessed.
DISSEMINATION OF OUTPUTS
Atomic Data and Spectroscopy
The web-based Atomic Spectra Database (ASD) is a great success. The group has continued to update and modernize the ASD interface to make it increasingly useful.
Spectroscopy will continue to be an important diagnostic for many industrial processes.
Experimental Solid State Quantum Information
The PML research in this area is highly visible through publications and conference presentations.
The need for isotopically pure silicon from multiple research areas is becoming increasingly clear. A modest investment in the small electromagnetic (mass spectrometer) isotope separation system would be valuable. The isotopically pure silicon would be more readily available to internal NIST users and, to the extent that it could be shared with researchers outside NIST, could be used to foster collaborations. It is not necessary to scale up to the large gas centrifuge separation scale that supplies the German Physikalisch-Technische Bundesanstalt (PTB) with macroscopic artifacts of isotopically pure silicon.
Experimental Cold Atoms, Quantum Optics, Nanomechanical Science, and Theory
The results of the research in this area are disseminated in leading journals and at conferences with invited papers and through college courses at the University of Maryland.
In collaboration with JQI and QuICS, teaching presents an opportunity to disseminate results and train future scientists. JILA has a long and successful tradition along these lines, and a similar outcome can be expected from JQI as it further establishes itself.
Fundamental Electrical Measurements, Applied Electrical Metrology, Mass and Force
The dissemination of primary units realizations is an extremely important mission and needs to be supported, with the focus on making the secondary units cheaper but with even more manageable uncertainties. The educational and training efforts for the customers who use the standards are also important.
The PML has provided leadership in smart grid technologies, mainly in synchrophasor measurements and interoperability of metering devices. The PML can leverage its work in the timing standards, atomic clock in a chip, and NIST-on-a-Chip, to develop inexpensive standards for reliable, time-synchronized and interoperable and cybersecure metering standards. For smart grid applications, a timing accuracy of 1 microsecond is acceptable. While the PML has engaged a small section of industry, it is important to increase that engagement.
The dissemination of the work in the new area of smart grid technologies may pose some challenges in balancing the metrology and standards mission of NIST with industrial and commercial interests.
