In earlier parts of this web site for the Quantum Electrical Metrology Division, we discuss standards based either directly or indirectly on naturally occurring quanta.
In this section we present measurements , but not standards, many of which are achieved using quantum systems. Predominantly the system used is superconductivity, which is a macroscopic quantum system. Superconductors are particularly attractive for electrical metrology because they can carry current with very low loss, and with zero loss if the current is constant.
For measurements for quantum communications we use superconducting microcalorimeters to count single photons, the quanta of light. We use similar devices for X-ray microanalysis of materials and as ultra-sensitive or ultra-accurate detectors of infrared and X-ray radiation. Other superconducting detectors are use for terahertz frequency radiation. Our measurements of high-frequency electrical pulses and electrical power are based on fundamental standards that in turn rely on superconductors.
In a completely different way we are using superconductivity to contribute to a major NIST and international effort to realize the concept of quantum computing. If a quantum computer can be practically realized, it may be capable of vastly more computational power than any other known computing technique. It is of potentially profound national importance. As a result, NIST is investing heavily in this area because it is a very challenging measurement problem. Measurements are NIST's expertise and we are able to make essential contributions to this exciting technology.
Quantum computing is completely different from the computing we know. It relies on the manipulation of the wave functions that are the basis of quantum systems. The measurement of the output from a quantum computer is performed at the very fundamental limit of measurements, based on the Heisenberg uncertainty principle. As a result we are striving to realize measurement of unprecedented delicacy, using approaches that surely will be of use much broader than just quantum computing as we progress through the 21st century.