Speaker
Description
Entanglement swapping enables entanglement to be shared between two parties that have never directly interacted. Two independent entangled pairs are prepared; one mode from each pair is sent to a central relay, where a joint Bell-type measurement is performed. Conditioned on the measurement outcome, the two remote retained modes are projected into an entangled state. This mechanism is a core building block of quantum repeater architectures and necessary for long distance quantum communication. In previous work, Ottaviani et al. introduced a multipartite entanglement swapping protocol for continuous-variable systems. The protocol considers N users, each initially possessing an identical two-mode Gaussian state. Each user retains one mode locally while sending the other to a central node, where a multipartite Bell measurement is performed. In the original protocol, this Bell measurement is implemented using homodyne detection. In this work, we investigate the effect of replacing the homodyne measurement with photon-number-resolving (PNR) detection. We find that, although replacing the homodyne measurement with PNR detection renders the entanglement swapping protocol probabilistic, it significantly improves the protocol's robustness to loss on the modes transmitted to the relay station. As channel loss increases, the homodyne-based protocol exhibits entanglement death at transmissivities of 0.5, 0.6 and 0.7 for N = 2, 3, and 4 users, respectively. In contrast, the PNR-based protocol continues to generate non-zero conditional entanglement across a far greater range of transmissivities. Overall, these results highlight the important role that non-Gaussian operations play in improving the performance of continuous-variable entanglement distribution protocols.
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