Entanglement across separate silicon dies in a modular superconducting qubit device

Assembling future large-scale quantum computers out of smaller, specialized modules presents significant science and engineering challenges. The primary challenge is the development of high-fidelity, low-latency quantum interconnects. This study demonstrates a modular solid-state architecture facilitating deterministic inter-module coupling among four separate superconducting qubit integrated circuits. We achieved impressive two-qubit gate fidelities of 99.1 ± 0.5% and 98.3 ± 0.3% for iSWAP and CZ gates, respectively. The quality of the resultant inter-module entanglement was validated through Bell-inequality violation for disjoint pairs of entangled qubits across the separate silicon dies. This work lays the technological groundwork for a modular quantum processor, crucial for advancing near-term experimental initiatives and paving the way towards fault-tolerant capabilities in solid-state qubit architectures.