DC flux crosstalk reduction with dual flux line

Flux-tunable superconducting qubits offer the potential for quantum information processing and simulation. However, flux crosstalk complicates achieving precise qubit frequency control, as characterizing and compensating for it becomes more challenging when scaling up circuits. In this study, we propose a design featuring a dual flux line for flux-tunable superconducting qubits, consisting of a pair of parallel current lines directing the current back to the enclosure. We conduct experimental comparisons of the DC flux crosstalk between the dual flux line design and the traditional one-way approach within a single chip. We observe a significant reduction in the DC flux crosstalk when utilizing the dual flux line, as supported by electromagnetic field simulations. Our design introduces an approach to scaling up flux-tunable superconducting circuits while maintaining a modest on-chip footprint.