Entanglement swapping of polarization entangled photon pairs from Doppler-broadened atomic ensemble.

We experimentally observed entanglement swapping of two independent polarization entangled photon pairs generated by spontaneous four-wave mixing(SFWM) in Doppler-broadened $^{\mathrm{87}}$Rb atomic ensemble. Polarization entangled photon pairs are generated in sagnac interferometer configuration which enable us to produce four Bell states in stable condition and performed Bellstate analysis with a fidelity of 93{\%}. We also demonstrated entanglement swapping by utilizing the polarization entangle photon pairs with polarization projective measurement. The results shown here would be an important contribution to an atom-photon interface in the field of quantum optics.