Polarization-based entanglement swapping at the telecommunication wavelength using spontaneous parametric down-conversion photon-pair sources
Yinghong Xue, Akio Yoshizawa, Hidemi Tsuchida · Physical Review A · 2012
We experimentally demonstrated polarization-based entanglement swapping using spatially separated periodically poled lithium niobate waveguides that emit polarization-entangled photon pairs by spontaneous parametric down-conversion (SPDC). Entanglement swapping using such SPDC sources was theoretically analyzed by accounting for losses along photon propagation paths, accidental fourfold coincidence counts (FCC's), and the dead time in single-photon detection. In a partial Bell-state measurement, entanglement was observed between two photons that were initially uncorrelated and that did not directly interact with each other. The obtained fidelity was $52.5\ifmmode\pm\else\textpm\fi{}0.8%$. Accidental FCC's were measured to clarify the effect of simultaneous generation of three pairs in SPDC on the fidelity. The fidelity increased to $80.5\ifmmode\pm\else\textpm\fi{}2.9%$ when accidental coincidence counts were subtracted.