Single-photon-boosted type-I fusion gates

Abstract:Fusion measurements are a key primitive for linear-optical quantum computing and quantum networks. Type-I and type-II fusion gates are widely used to combine small entangled resource states into larger photonic states, but without ancillary resources their success probability is limited to $1/2$. Existing $3/4$-efficient type-I schemes rely on entangled Bell-pair ancillary states, whose preparation is itself probabilistic and resource-intensive. Here we propose a boosted type-I fusion gate using only four ancillary single photons and standard linear-optical primitives. For multiqubit GHZ and graph states, the gate succeeds directly with probability $5/8$, while a distillation protocol converts partially entangled outcomes into additional successful events, raising the total success probability to $11/16$ after one stage and asymptotically to $3/4$. We quantify the practical advantage of this scheme by estimating the photonic resources required for generating representative large entangled photonic states and show that the proposed gate significantly reduces the required overhead compared with existing schemes. These results expand the set of resource-efficient linear-optical primitives and enable a substantial reduction in the resource requirements for scalable photonic quantum computing and quantum communication.

13 pages, 5 figures; v2: Sec. IV extended to include additional schemes; v3: comparison with existing schemes added to Sec. IV and discussion expanded

arXiv:2603.27315 [quant-ph]

(or arXiv:2603.27315v3 [quant-ph] for this version)