The multiphoton states generated by high-gain spontaneous parametric down-conversion (SPDC) in the presence of large losses are investigated theoretically and experimentally. The explicit form for the two-photon output state has been found to exhibit a Werner structure very resilient to losses for any value of the nonlinear gain parameter $g$ . The theoretical results are found to be in agreement with experimental data obtained by ``entanglement witness'' methods and by the quantum tomography of the state generated by a high- $g$ SPDC.The multiphoton states generated by high-gain spontaneous parametric down-conversion (SPDC) in the presence of large losses are investigated theoretically and experimentally. The explicit form for the two-photon output state has been found to exhibit a Werner structure very resilient to losses for any value of the nonlinear gain parameter $g$. The theoretical results are found to be in agreement with experimental data obtained by ``entanglement witness'' methods and by the quantum tomography of the state generated by a high-$g$ SPDC.

arXiv:quant-ph/0510153Physical Review AMar 14, 200624 citations

Information-theoretic aspects of Werner states

Nan Li, Shunlong Luo, Yuan Sun

Annals of PhysicsNov 29, 202017 citations

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. The theoretical results are found to be in agreement with experimental data obtained by ``entanglement witness'' methods and by the quantum tomography of the state generated by a high-

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SPDC.