High-efficiency quantum state transfer for modular networks

Bosonic modes in superconducting cavities have broad applications in quantum computation, quantum error correction, and quantum simulation. However, scaling up superconducting cavities remains a challenge, and one potential solution is modular quantum computation. In this work, we achieve a low-loss interconnect between two superconducting cavities using an aluminum coaxial cable, with the bus mode quality factor of 1.6×10⁶. By using SNAIL as couplers, we realize inter-modular state transfer within a time of 0.7 μs via three-wave mixing process. The fidelities of state transfer for quantum states encoded in the first two energy levels and binomial codes reach 98.2% and 94.7%, respectively. Additionally, we implement entanglement distribution between the two modules, achieving a Bell state fidelity of 92.5%. Our work lays the foundation for future multi-module bosonic-mode quantum networks.