Work of physicists at the University of Geneva (UNIGE), Switzerland, and the Swiss Federal Institute of Technology in Zurich (ETH Zurich), in which they connected two materials with unusual quantum-mechanical properties through a quantum constriction, could open up a novel path towards both a deeper understanding of physics and future electronic devices. Their results have just been published in the journal Science.

The researchers work with that are trapped in laser beams and thus isolated from any external disturbance. Lasers are also used to cool the atoms to temperatures lower than those found anywhere else in the entire Universe. These 'ultracold' temperatures then enable creating clean materials that possess intriguing quantum-mechanical properties, such as unusual superconductivity. Thierry Giamarchi, professor at the UNIGE and responsible for the theoretical part of the study, explains: "In a cold-atom superconductor, the particles interact very strongly, whereas the interaction is usually very weak. This brings out strong-interaction effects through cooling could be compared to freezing water: the basic system is the same, but the result after cooling is very different."

The experimental team in Zurich, led by Tilman Esslinger and Jean-Philippe Brantut, has now overcome the challenges to efficiently transport between two quantum superconductors with strong interactions through a single quantum point, a so-called quantum point contact. "With this new quantum connection, we can now reveal new effects in these superconducting quantum systems. It is a fundamental breakthrough in the way we can use quantum physics with ", says Giamarchi, from UNIGE's Faculty of Science.

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