Deterministic and Programmable Fusion for Scalable Generation of Photonic Graph States

Photonic graph states are central to various applications such as measurement-based quantum computing and distributed quantum networks. While fusion promises scalable generation of large-scale graph states by linking small resource states, conventional probabilistic protocols incur heavy overheads. In this talk, I will introduce a deterministic fusion operation that nondestructively projects pairs of flying microwave photonic qubits into Bell states using in-situ programmable superconducting circuits, thereby reliably linking small time-bin-encoded cluster states into larger and reconfigurable graphs. The protocol features active matter-qubit reset and reuse, decoupling graph growth from emitter coherence. We experimentally generate genuine multi-partite entanglement among 13 photonic qubits, demonstrating scalability and flexibility of the approach. By removing the probabilistic bottleneck of conventional fusion, our method establishes a practical pathway to large-scale photonic graph-state synthesis.