Entanglement swapping between discrete and continuous variables

TL;DR

This paper demonstrates a successful experimental realization of hybrid entanglement swapping between discrete and continuous variable optical systems, enabling enhanced quantum communication protocols.

Contribution

It introduces a novel hybrid entanglement swapping method combining DV and CV systems using squeezed light and homodyne detection, verified without post-selection.

Findings

DV entanglement verified with logarithmic negativity of 0.28

Post-selected states violate CHSH inequality by over four standard deviations

Efficient transfer of entanglement between DV and CV systems

Abstract

We experimentally realize "hybrid" entanglement swapping between discrete-variable (DV) and continuous-variable (CV) optical systems. DV two-mode entanglement as obtainable from a single photon split at a beam splitter is robustly transferred by means of efficient CV entanglement and operations, using sources of squeezed light and homodyne detections. The DV entanglement after the swapping is verified without post-selection by the logarithmic negativity of up to 0.28$\pm$0.01. Furthermore, our analysis shows that the optimally transferred state can be post-selected into a highly entangled state that violates a Clauser-Horne-Shimony-Holt inequality by more than four standard deviations, and thus it may serve as resources for quantum teleportation and quantum cryptography.