High-fidelity entanglement swapping at telecommunication wavelengths
Qing-Lin Wu, Naoto Namekata, Shuichiro Inoue · Journal of Physics B Atomic Molecular and Optical Physics · 2013
We have demonstrated entanglement swapping with 1550 nm polarization-entangled photon pairs created by spontaneous parametric down conversion in two spatially separated type-II periodically poled lithium niobate bulk crystals. In a partial Bell-state measurement, entanglement was observed between two photons from separate sources. We employed sinusoidally gated InGaAs/InP avalanche photodiodes operated at a repetition frequency of 1.28 GHz, which increased the four-fold coincidence count rate without degrading the fidelity of entanglement swapping. The obtained fidelity exceeds 90%, which indicates that the entangled states obtained in this experiment are high enough for immediate further use in quantum communication protocols such as quantum teleportation or quantum cryptography.