Amazing stuff, but a bit aged (first published in July 2023). Precise measurements take time to polish! 😊
"A team of scientists has revealed how a single quantum device can accurately measure the three fundamental units of electricity—the ampere (unit of electrical current), the volt (unit of electrical potential) and the ohm (unit of electrical resistance). This is a significant breakthrough because until now, no single instrument could measure all three primary electrical units in one practical system. It means that making electrical measurements could be more precise and reduce the potential for human error. ...
the device is possible by integrating two key quantum systems into a single cryostat. Namely, a special type of resistor called a quantum anomalous Hall resistor (QAHR) and a programmable Josephson voltage standard (PJVS). The cryostat provides the right low-temperature environment for both of them to operate effectively. ...
Using this new technology, the researchers measured voltages from 0.24 millivolts to 6.5 millivolts with very little error. They also made extremely precise measurements of resistance and electrical current. ..."
"Researchers ... have developed one of the first all-in-one instruments for realizing the most up-to-date standards for voltage, resistance, and current. The prototype instrument—a sort of Swiss Army knife for electrical standards—could pave the way for a compact tool that would save both time and money by enabling engineers in their own laboratories to directly calibrate electrical equipment to international standards. ...
The relative accuracy of the new instrument for voltage, resistance, and current is several parts in a million, comparable to the best calibration and measurement capabilities of national metrology institutes across the globe. ..."
From the abstract:
"In the revised International System of Units (SI), the ohm and the volt are realized from the von Klitzing constant and the Josephson constant, and a practical realization of the ampere is possible by applying Ohm’s law directly to the quantum Hall and Josephson effects. As a result, it is possible to create an instrument capable of realizing all three primary electrical units, but the development of such a system remains challenging.
Here we report a unified realization of the volt, ohm and ampere by integrating a quantum anomalous Hall resistor (QAHR) and a programmable Josephson voltage standard (PJVS) in a single cryostat.
Our system has a quantum voltage output that ranges from 0.24 mV to 6.5 mV with combined relative uncertainties down to 3 μV V−1. The QAHR provides a realization of the ohm at zero magnetic field with uncertainties near 1 μΩ Ω−1. We use the QAHR to convert a longitudinal current to a quantized Hall voltage and then directly compare that against the PJVS to realize the ampere.
We determine currents in the range of 9.33–252 nA, and our lowest uncertainty is 4.3 μA A−1 at 83.9 nA. For other current values, a systematic error that ranges from −10 μA A−1 to −30 μA A−1 is present due to the imperfect isolation of the PJVS microwave bias."
All In One: NIST Develops Single Device to Realize Electrical Standards (original news release) "Prototype instrument may enable industry and the military to calibrate electrical equipment to international standards in their own laboratories."
A unified realization of electrical quantities from the quantum International System of Units (no public access)
A unified realization of electrical quantities from the quantum International System of Units (preprint, open access)
A new instrument developed at NIST realizes the most up-to-date standards for voltage, resistance, and current in a single cryostat.
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