Atomic Josephson contacts: How Bose-Einstein condensates replicate Shapiro steps

German researchers at RPTU University replicated the Josephson effect using ultracold atoms instead of superconductors, offering a new quantum simulation approach to study microscopic supercurrent dynamics. The team used two Bose-Einstein condensates separated by a thin optical barrier—mimicking a Josephson junction—to observe quantum tunneling behavior analogous to superconducting pairs crossing an insulating gap. Published in December 2025, the experiment marks the first direct observation of Shapiro steps in BECs, where an external AC drive induces quantized voltage steps, mirroring superconducting Josephson junction behavior. This atomic-scale simulation provides a controllable platform to probe quantum coherence and tunneling mechanisms, bypassing the technical challenges of studying real superconductors at microscopic levels. The breakthrough could advance quantum metrology and fault-tolerant qubit designs by leveraging BECs as tunable, noise-resistant quantum simulators for superconducting phenomena.