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Quantum Measurement Division

The Quantum Measurement Division (QMD) provides the physical foundation for the International System of Units (Système International d'Unités or SI), colloquially referred to as the metric system.

We achieve this through precision measurements of various fundamental constants, realization of resistance and voltage through the quantum hall effect and Josephson effect respectively, and through our determination of the best values of the fundamental constants done under the auspices of the Task Group on Fundamental Constants of the Committee on Data for Science and Technology (CODATA, an interdisciplinary unit of the Scientific Committee of the International Council for Science).

The division is currently heavily engaged in the redefinition of the SI that is expected to occur in 2018. We support this effort through R&D and through interactions with the International Bureau of Weights and Measures (BIPM) and its consultative committees including the Consultative Committee for Units (CCU), the Consultative Committee for Electricity and Magnetism (CCEM), and the Consultative Committee for Mass and Related Quantities (CCM).

As part of this effort, NIST is building a new Watt Balance which - prior to the redefinition -will be used to make one final precision measurement of the Planck constant. After the redefinition, it will become the means for the realization of the kilogram in the United States.

The planned redefinition of the SI in 2018 will achieve the goal of turning the SI into a system based on fundamental constants and properties of nature. In fact, the new redefined SI will be largely based on quantum mechanics and its generalizations. including quantum electrodynamics.

As such, the strategy of the QMD is to:

  • investigate and exploit quantum behavior to create measurement tools and capabilities at and beyond the standard quantum limit
  • explore the basic capabilities of complex quantum systems to better understand what future quantum technologies will allow us to measure, compute, and simulate
  • exploit this knowledge to create the foundation to realize and disseminate mass, force, and electrical quantities and improve our ability to realize these quantities
  • disseminate these quantities from first principles, through specially developed instruments and methodologies, or through scaling that minimizes the loss of accuracy of the various technologies involved relative to the best available quantum or classical technology
  • to create critically evaluated data relevant to both fundamental constants and atomic properties

Redefining the Kilogram

K20 prototype mass

For more than a century, the kilogram (kg) — the fundamental unit of mass in the International System of Units (SI) — was defined as exactly equal to the mass of a small polished cylinder, cast in 1879 of platinum and iridium.

Kept in a triple-locked vault on the outskirts of Paris, the platinum-iridium cylinder was officially called the International Prototype of the Kilogram (IPK). It even had a nickname: Le Grand K (The Big K). The accuracy of every measurement of mass or weight worldwide, whether in pounds and ounces or milligrams and metric tons, depended on how closely the reference masses used in those measurements could be linked to the mass of the IPK.

That situation has changed radically. In November 2018, the international scientific community voted to redefine the kilogram, freeing it from its embodiment in one golf-ball-sized artifact, and basing it instead on a constant of nature. That transformation was as profound as any in the history of measurement. MORE

News and Updates

Now Hear This!

Researchers at the National Institute of Standards and Technology (NIST) have designed and built an optical device that could set a new standard for measuring

Industry Impacts

Massive Forces for Heavy Industry

Measuring large forces, such as the thrust of a rocket engine or the deflection of an aircraft wing, requires well-calibrated force sensors. NIST’s unique

Projects and Programs

AC-DC Difference

The NIST Ac-dc2 Difference Project performs leading edge measurement services and research for ac-dc difference measurements and dc voltage metrology. We

Applications of Quantum Information

Theory is being developed and used to devise methods for preserving and exploiting the quantum behavior of ever-larger systems for metrology, communication, and

Atomic Spectroscopy Data Center

Critical compilations of atomic energy levels, transition wavelengths, and transition probabilities. Online databases.

Calibration of Force Transducers

NIST provides calibration services for force-measuring instruments by applying known forces, compression, tension or both, to the elastic transducer and



Press Coverage

A more perfect unit: the new mole

Popular Science
A video about the redefinition of the mole, featuring NIST's Savelas Rabb, Robert Vocke, and Stephan Schlamminger.


A timeline of long distance communication techniques

Communication Linker for Communication Linking

NIST Inventors
Sergey Polyakov and Ivan Burenkov
Patent Description The US has the leading optical communication industry and one of the largest telecommunication markets. Our invention directly improves the underlying technology of the telecommunication infrastructure. Quantum Coherent Frequency Shift Keying (CFSK) receiver is a device that
This image of a chart titled "How does it work" that describes the optomechanical reference.

Optomechanical Reference

NIST Inventors
Gordon A. Shaw and Jacob Taylor
A mechanical sensor incorporating an optical cavity is used to provide a mass and/or force reference from a known or characterized circulating optical power in the optical cavity. The radiation pressure force in the optical cavity is used to actuate the mechanical sensor. The optical cavity in put


Division Chief