Six-photon entangled Dicke state enabled by a UV enhancement cavity as novel SPDC photon source

Photon sources for multi-photon entanglement experiments are commonly based on the process of spontaneous parametric down conversion. Due to the probabilistic photon production, such experiments suffer from low multi-photon count rates. To increase this count rate, we present a novel SPDC pump source based on a femtosecond UV enhancement cavity that increases the available pump power while maintaining a high repetition rate of 80 MHz. We apply the cavity as photon source for realizing symmetric, multi-partite entangled Dicke states, which are observed with a high rate and high fidelity. We characterize the observed Dicke states of up to six photons using efficient tools exploiting the state's symmetries.