Miniaturized qubits gain connectivity with a new coupler design

The work proposes using SQUID couplers with relatively small Josephson energies, a departure from typical approaches that seek larger values, to minimize errors caused by “dynamical variations in mode hybridization” and resulting non-adiabatic transitions. This junction-based design maintains a strong qubit interaction while limiting undesired mixing between elements, enabling a fast, high-fidelity controlled-Z gate. The authors present a scalable tiling strategy for a miniaturized superconducting quantum processor based on merged-element transmon qubits. SQUID couplers employing relatively small Josephson energies offer a pathway to denser superconducting circuits, addressing limitations inherent in traditional capacitive coupling schemes. This design choice actively reduces Josephson energy, typically maximized in these devices, to maintain interaction at a perturbative scale, limiting unwanted mixing between…