Nonreciprocal qubit coupling through superconducting diodes for modular quantum circuits

We leverage superconducting diodes to realize an on-chip nonreciprocal qubit coupler. Superconducting qubits offer a promising platform for scalable quantum computing, but their connectivity is typically restricted to nearest neighbors, and conventional approaches to directional coupling rely on bulky or lossy components. By embedding the characterized diode element into a resonator, we engineer direction-dependent impedance that mediates passive, intrinsic nonreciprocal coupling between two qubits. We demonstrate coherent control of directional population transfer, implement a directional iSWAP gate with tunable phase, and achieve Bell-state generation dependent on coupling direction. This device-level nonreciprocity enables resource-efficient, low-loss architectures for modular and fault-tolerant superconducting quantum processors.