The Josephson diode, a nonreciprocal quantum element analogous to the familiar semiconductor p–n junction diode, has been realized in solid-state systems. However, it remains relatively unexplored in atomtronic circuits, which, in contrast to the solid state, allow real-time, in situ, and tunable control over key elements such as junction geometry, current-phase relationship, symmetry breaking, and interaction-induced nonlinearity. In this Letter, we propose and numerically demonstrate the realization of the Josephson diode effect in an atomtronic circuit consisting of a ring-shaped Bose-Einstein condensate and with optical barriers serving as Josephson junctions. Our implementation of this macroscopic nonreciprocal quantum phenomenon is based on realizing the required inversion symmetry breaking through asymmetric barrier placement and an asymmetric alternating current drive, enabling position- and drive-tunable diode effects with efficiencies up to 20% and 91%, respectively. While standard time-of-flight absorption imaging can readily observe these effects, we employ cavity optomechanics for cleaner, in situ, real-time, and nondestructive measurements of the relevant condensate dynamics. Our results establish a highly tunable platform for nonreciprocal Josephson transport, opening avenues for diode-based neutral-atom technologies in future quantum circuits.

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• Atomtronics
• Bose-Einstein condensates