Researchers from the Laboratoire National d’Essais (LNE) have developed a quantum current standard able to generate currents of values in a range from microamperes (10-6 A) to milliamperes (10-3 A) accurately linked to the elementary charge with a targeted relative uncertainty of 10 parts in a billion.

Schematic representation of a combined quantum “voltage and resistance”-based current source

This breakthrough relies on an error-free application of the Ohm’s law to the highly accurate quantum standards of resistance and voltage, based on two macroscopic quantum effects linked to fundamental constants, the quantum Hall effect and the Josephson effect, occurring in two-dimensional semiconductors and superconductors respectively.
This novel quantum current generator improves the accuracy of current standards by two orders of magnitude and paves the way to fully quantum-based electrical measurements in the SI.

This research was published open-access in Physical Review X (PRX) journal of the American Physical Society:
J. Brun-Picard, S. Djordjevic, D. Leprat, F. Schopfer and W. Poirier
“Practical Quantum Realization of the Ampere from the Elementary Chargeˮ, Phys. Rev. X, 6, 041051 (2016).

See also “A new era for the ampere” by Mark Keller from NIST, the National Measurement Institute for the United States.