NIST has developed advanced quantum voltage standards that have significantly improved the accuracy of electrical measurements. The first programmable quantum voltage standard was created in 1990, using Josephson junctions to generate precise voltage levels. This was followed by the development of ac quantum voltage standards in the 1990s, which enabled more accurate measurements of alternating current.
In 2000, NIST introduced a new soldered, flex-bonded package for their quantum voltage standards, which was more reliable than the previous spring fingerboard design. This chip had double-stacked junctions, allowing it to produce twice the maximum voltage of the original programmable standards.
In 2004, NIST used their Gaithersburg voltage laboratory to redefine the kilogram using a watt balance experiment, which relied on their quantum voltage standards. This experiment demonstrated the potential of quantum-based measurements to redefine fundamental units of measurement.
In 2005, NIST developed the first ac-to-dc voltage calibrations using their quantum voltage standards, which improved the accuracy of power and energy meter calibrations. This was followed by the creation of the “quantum watt,” a quantum-based ac power standard that reduced measurement uncertainty for power grid calibrations.
In 2010, NIST introduced a 10-volt programmable standard with triple-stacked junctions, capable of both ac and dc voltage measurements. This standard had a more stable quantized step and uniform electrical properties than previous designs.
In 2011, NIST researchers used a quantum-voltage-based Johnson noise thermometer to make the first practical electronic measurement of the Boltzmann constant, a fundamental constant important for temperature measurement. This technique was simpler and more compact than gas-thermometry methods and could advance international efforts to revamp the world’s scientific measurement system.
Keywords: voltage, Josephson, niobium, device, metrology
