Ultracold atoms reveal Shapiro effect that bridges two quantum worlds

Researchers at Rhineland-Palatinate Technical University (RPTU) in Germany have successfully recreated the Josephson effect—a fundamental quantum phenomenon critical to technologies like quantum computers and voltage standards—using ultracold atoms instead of solid-state superconductors. By employing Bose–Einstein condensates (BECs) separated by a thin optical barrier formed by a laser, they created an atomic analog of a Josephson junction. Modulating the barrier’s motion mimicked microwave radiation, leading to the direct observation of Shapiro steps, quantum features previously thought exclusive to superconducting systems. This experiment not only visualized excitations underlying the Shapiro effect for the first time but also demonstrated its universality across distinct quantum systems. The findings bridge the quantum behaviors of electrons and atoms, showing that Shapiro steps depend fundamentally on constants and driving frequencies rather than the nature of the particles involved. The atomic system offers a novel platform to study quantum phenomena such as dissipation and coherence with greater visibility than solid materials allow. While