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Overview of the Physical Measurement Laboratory

The Physical Measurement Laboratory (PML) of the National Institute of Standards and Technology (NIST) is the U.S. agency responsible for setting the measurement standards for time, length, mass, and many other physical qualities. These standards are crucial to industry, academic research, medicine, government agencies, and to many other parts of society. Thus, one major responsibility of PML is to develop, maintain, and disseminate the official standards for such things as length, mass, force and shock, acceleration, time and frequency, electrical units, temperature, humidity, pressure and vacuum, liquid and gas flow, optical quantities, acoustic quantities, and ionizing radiation (NIST 2022).

In support of its work in setting measurement standards, the laboratory carries out a wide range of research related to measurement and to the development of measurement technologies. For example, it establishes spectroscopic methods and standards for infrared, visible, ultraviolet, X ray, and gamma-ray radiation. It also carries out research into the structure and dynamics of atoms, molecules, and biomolecules; it develops and improves the electrical, thermal, dimensional, mechanical, and physical metrology used to measure the properties of precision measurement devices and exploratory semiconductor, quantum electronic, nano-electronic, bioelectronic, bio-optical, optoelectronic, and quantum information devices and systems; and it studies the thermophysical and interfacial properties of streams of flowing fluids, fluid mixtures, and solids. In addition to those fundamental research efforts, PML also generates, evaluates, and compiles atomic, molecular, optical, ionizing radiation, electronic, and electromagnetic data; it measures and improves the accuracy of the fundamental physical constants; and it develops and operates major radiation sources used in measurement science and metrology (NIST 2023a).

In its role as the developer, repository, and disseminator of national measurement standards, PML works to promote uniformity and accuracy at the international, federal, state, and local levels through the development and sharing of calibrations, measurement quality assurance, and standard reference materials as well as through technology transfer, education and training, and a comprehensive weights and measurement program.

PML comprises nine separate divisions, each devoted to a particular aspect of measurement science and technology. Five of those divisions are in Gaithersburg, Maryland: Microsystems and Nanotechnology, Nanoscale Device Characterization, Quantum Measurement, Radiation Physics, and Sensor Science. The office of Weights and Measures is also located in Gaithersburg. The remaining four are in Boulder, Colorado. One division, Quantum Physics, is found on the University of Colorado Boulder campus. The other three—Applied Physics, Quantum Electromagnetics, and Time and Frequency—are on the NIST Boulder campus.

This report is concerned with the four divisions located in Boulder: Applied Physics, Quantum Physics, Quantum Electromagnetics, and Time and Frequency. A brief description of each of those four divisions follows.

APPLIED PHYSICS DIVISION

The laboratory’s Applied Physics Division is focused mainly on measurements involving electromagnetic radiation across its entire spectrum, working to advance measurement science and technology in many critically important areas, including national security, advanced manufacturing, quantitative imaging, strategic computing, and quantum communications (NIST 2023b). To that end, the division operates a cutting-edge precision imaging facility that characterizes devices used for measurements and standard setting. The division’s metrological expertise is vital to the development of many transformative technologies, including photonics, magnetics, and imaging. Its staff include world-class experts in laser and quantum metrology, quantitative imaging, spectroscopy, advanced communications, sensing, laser safety, and photonic and magnetic applications. The beneficiaries of its research and expertise are found throughout industry, academia, and government.

The division includes the following seven individual research groups:

• Advanced Microwave Photonics Group
• Faint Photonics Group
• Magnetic Imaging Group
• Molecular and Biophotonics Group
• Quantitative Nanostructure Characterization Group
• Quantum Nanophotonics Group
• Sources and Detectors Group

Specific areas of focus in the seven research groups include optical power measurements, quantum information, magnetic imaging, terahertz imaging research, research in optical frequency combs (used for precision time and frequency measurements) and quantum nanostructure characterization.

QUANTUM PHYSICS DIVISION

The Quantum Physics Division is the NIST component of JILA, a physical science research institute which is a collaboration between NIST and the University of Colorado Boulder, where JILA has its physical presence. At JILA, which was previously known as the Joint Institute for Laboratory Astrophysics, scientists carry out both theoretical and experimental research aimed at advancing fundamental measurement science. Studies focus on such topics as the quantum physics underlying interactions between light and matter and the ultimate limits of quantum measurements (NIST 2022), with specific areas of interest including quantum information science, quantum-enhanced precision measurement, ultracold atoms and molecules, quantum many-body physics, chemical physics, biophysics, and nanoscale quantum science (NIST 2023c). In addition to research, the division also emphasizes the training of scientific leaders and innovators for jobs in academia, industry, and national laboratories.

The division’s primary research and training focus areas are as follows:

• Quantum information science and technology
• Precision measurement
• Atomic and molecular physics
• Laser physics
• Chemical physics
• Biophysics

QUANTUM ELECTROMAGNETICS DIVISION

The mission of the Quantum Electromagnetics Division is to “provide the metrological foundation for strategic, emerging electronic, magnetic, and photonic technologies by developing high-precision measurement devices, systems, standards, and methodologies and disseminating them to address national needs” (NIST 2023c). Taking advantage of the electronic, magnetic, quantum-mechanical, and photonic properties of materials and the interactions of those materials with electromagnetic waves, the researchers in the division develop high-precision measurement tools that can be used for quantum-based electrical standards, high-resolution photon sensors for imaging and spectroscopy, and energy-efficient spintronic devices (NIST 2022). The division’s capabilities are valuable in a wide variety of fields, including advanced computing, new analytical tools and reference data, instrumentation for astrophysics and cosmology, and quantum information science, artificial intelligence, superconducting quantum information, and hyper-dimensional imaging as well as in fundamental physics. As is the case in the other divisions, the staff of the Quantum Electromagnetics Division collaborate and communicate with interested parties in academia, industry, and government to understand and address their measurement needs.

This division has the following five groups:

• Device Microfabrication Group
• Quantum Calorimeters Group
• Long Wavelength Sensors and Applications Group
• Quantum Electronics Group
• Spin Electronics Group.

Among its many activities, the division

• Operates a state-of-the-art Boulder microfabrication facility.
• Develops and disseminates instruments based on quantum sensors for the analysis of nuclear materials. These instruments provide new capabilities for precise, nondestructive composition measurements, and are in use at several nuclear facilities.
• Develops and disseminates large arrays of microwave polarimeters that are essential tools for modern cosmology.
• Develops new superconducting circuits for neuromorphic computing.
• Innovates in spin electronics and nanoscale spin dynamics research.
• Fabricates best-in-class, ultra-sensitive superconducting detector arrays (NIST 2022).

TIME AND FREQUENCY DIVISION

The missions of the Time and Frequency Division include maintaining the U.S. standards for frequency and time intervals, providing official time to the United States, and carrying out a broad program of research and service activities in time and frequency metrology (NIST 2023e). Thus, a major research thrust is dedicated to achieving an accurate and precise realization of Coordinated Universal Time (NASEM 2018), which is achieved with a cesium fountain atomic clock. The division also develops and maintains other technologies related to the measurement of time and frequency, including a ytterbium optical lattice clock, an aluminum ion quantum logic clock, optical frequency combs, the quantum control of single molecular ions, quantum information processing with trapped ions, quantum simulation and sensing with large trapped-ion crystals, chip-scale wavelength references and clocks, and microresonator devices. (NIST 2022).

The division currently has the following seven individual research groups:

• Atomic Devices and Instrumentation Group
• Ion Storage Group
• Neutral Atom Optical Clocks Group
• Phase Noise Metrology Group
• Precision Photonic Synthesis Group
• Quantum and Nonlinear Nanophotonics Group
• Time Realization and Distribution Group

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