Three-photon W-state
Nikolai Kiesel, Mohamed Bourennane, Christian Kurtsiefer, Harald Weinfurter, Dagomir Kaszlikowski, Wiesław Laskowski, Marek Żukowski · Journal of Modern Optics · 2003
Multiphoton entanglement is the basis of many quantum communication schemes, quantum cryptographic protocols, and fundamental tests of quantum theory. For entangled three-qubit states it has been shown that there are two inequivalent classes of states, under stochastic local operations and classical communications. The classes are represented by the GHZ- and W-state. The GHZ-state has been used to prove Bell's theorem without inequality. Contrary to the GHZ-state, the W-state shows high robustness of entanglement against photon loss. Here we show the first experimental results on the observation of the polarization entangled three-photon W-state from spontaneous parametric down-conversion.