An international collaboration, including researchers from the National Physical Laboratory (NPL) and Royal Holloway, University of London, has successfully demonstrated a quantum coherent effect in a new quantum device made out of continuous superconducting wire – the Charge Quantum Interference Device (CQUID).

This research represents an important milestone towards the demonstration of a robust new quantum standard for electric current, and could be capable of disseminating the new definition of the ampere, which is expected to be decided on by the global measurement community as part of the redefinition of the international system of units (SI) later this year.

As published in Nature Physics, the device acts in the opposite way to the better-known superconducting quantum interference device (SQUID), used as an ultrasensitive sensor for magnetism. Instead of sensing a magnetic field via its influence on the current flow (moving charge) like a SQUID, the CQUID works seemingly in the opposite way, sensing charge as a result of quantum interference due to the flow of magnetic flux.

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