Long-range coupler for superconducting qubits using multimode filters

Coupling superconducting qubits separated by centimeter-scale distances is crucial for scalable architectures, for instance in the implementation of quantum low-density parity-check (LDPC) codes [1]. However, long-range couplers remain less explored than their local counterparts, and the optimal design for such long-distance coupling is still unclear. In this talk, we explore the use of on-chip filters as coupling elements between spatially-separated qubits. We show that, with a novel yet simple design inspired by previous proposals [2,3], it is possible to achieve a larger on/off coupling ratio while remaining robust to deviations in circuit parameters. Furthermore, by leveraging the multimode nature of the coupler, we show that fast, high-fidelity entangling gates can be realized, reaching performance levels typical of local coupling schemes.