Superconducting circuits pass Bell test

Researchers from the Swiss Federal Institute of Technology in Zurich (ETH) have proven that superconducting circuits function according to the laws of quantum mechanics. The group headed up by the solid state physics expert Andreas Wallraff subjected the circuits to a loophole-free Bell test, further details of which can be found in a press release. The evaluation of more than one million measurements showed that Bell’s inequality is violated by two entangled superconducting circuits with a very high statistical probability, which is in accordance with the laws of quantum mechanics.

Loophole-free Bell tests have already been performed on various quantum objects since 2015. However, measuring in at several hundred micrometers, superconducting circuits are considerably larger than microscopic quantum objects such as photons or ions. Moreover, they are considered to be “promising candidates for building powerful quantum computers”, as ETH writes in the press release. The successful experiments carried out by the researchers aiming to entangle superconducting circuits over a large distance therefore open up “interesting possible applications in the field of distributed quantum computing and quantum cryptography”, the press release states.

ETH Zurich highlights another potential application for this research. In cryptography, for example, modified Bell tests can be used to verify encryptions, according to Simon Storz, a member of the research group. “With our approach, we can prove much more efficiently than is possible in other experimental setups that Bell’s inequality is violated”, he explains. ce/hs