High-contrast interaction between remote superconducting qubits mediated by multimode cable coupling

Abstract: Superconducting quantum processors offer a promising path towards practical quantum computing. However, building a fault-tolerant quantum computer with millions of superconducting qubits is hindered by wiring density, packaging constraints and fabrication yield. Interconnecting medium-scale processors via low-loss superconducting links provides a promising alternative. Yet, achieving high-fidelity two-qubit gates across such channels remains difficult. Here, we show that a multimode coaxial cable can mediate high-contrast interaction between spatially separated super-conducting qubits. Leveraging interference between cable modes, we can implement high-fidelity controlled-Z and ZZ-free iSWAP gates by simply modulating qubit frequencies. Numerical simulations under realistic coherence and coupling parameters predict fidelities above 99% for both gate schemes. Our approach provides a versatile building block for modular superconducting architectures and facilitates distributed quantum error correction and large-scale fault-tolerant quantum computing.