Robust quantum standard for the electric current based on superconducting nanowires
When cooled below their critical temperature, superconducting nanowires with extremely small radii display behaviour contrary to their nature. Portions of the nanowire exhibit energy fluctuations that instantaneously resist current. Known as quantum phase slips, this phenomenon could be used as the dynamic equivalent quantum standard for voltage, which today is realised by arrays of Josephson junctions. The EU-funded project QUANTUM E-LEAPS project will exploit this quantum phenomenon occurring in superconducting nanowires to develop a WAY TO REALIZE a robust and easy-to-use universal quantum standard for the electric current on a single chip.
Objective
We will exploit new macroscopic quantum phenomena realised in superconducting nanowires made from 2D superconductors to trigger a paradigm change in electrical metrology. Our overall objective is to develop a robust and easy-to-use universal electrical quantum standard on a single chip by utilizing the duality of superconductive physics, which will allow direct traceability to the SI with no recourse to long calibration chains. Our main specific objective is to demonstrate a proof-of-concept quantum current standard using coherent quantum phase slips in superconducting nanowires (SNW). This effect is quantum-mechanically dual to the Josephson effect (which can be realised in the same superconductors) but yields quantised current reference rather than voltage. The exact duality suggests that the new current standard can be operated with the same user-friendly infrastructure and reach similar robustness and accuracy as the Josephson voltage standard. Such science-to-technology breakthrough can bring quantum-enabled accuracy directly to the end users. The combination of current and voltage standards - duals of each other - will enable all electrical quantum standards on a single chip.
Previous tentative experiments with SNW electronics encountered two general problems: sensitivity to the electromagnetic (EM) environment and SNW fabrication irreproducibility. We will solve these problems by unprecedented control of SNW. In particular, we will demonstrate gate-tuneable quantum phase slips in SNWs based on 2D superconductors and develop a tuneable EM environment for SNWs by using complementary metal-oxide semiconductor (CMOS) technology. These objectives will also lay foundations for future dual superconducting electronics, where SNW becomes a standard circuit element like Josephson junction is in conventional superconducting electronics.
