Multipartite entanglement swapping with homodyne and single photon detection

Abstract

Establishing multipartite entanglement across lossy optical networks remains a central challenge for distributed quantum information processing. Here, we consider a non-Gaussian continuous-variable entanglement-swapping protocol combining a symmetric discrete Fourier transform (DFT) interferometer with photon-number-resolving detection. In the ideal limit, single-photon heralding generates a $W_N$-class state across remote modes, with Fourier symmetry rendering all single-click outcomes equivalent up to local phase corrections. We find that conditional pairwise entanglement can exceed that of conventional Gaussian homodyne swapping in weak-to-moderate squeezing and lossy regimes, remaining nonzero beyond the channel-loss thresholds at which Gaussian pairwise entanglement vanishes. These results demonstrate that combining non-Gaussian measurements with symmetric interferometric mixing can improve both the resilience and operational efficiency of multipartite entanglement distribution in lossy quantum networks.