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Experimental Applications of a Linear Optical Controlled Phase Gate


I will present the experimental implementation of a probabilistic linear optical controlled phase gate. It is operating on the polarization degree of freedom of photons and is based on the second order interference at a ‘magic’ beam splitter. We characterized the gate performance with a tomographic set of measurements and, by fitting a model of the gate to the obtained data, we extracted the corresponding experimental parameters.

In a next step, the controlled phase gate served to entangle two EPR-pairs resulting in a four-photon entangled cluster state with a fidelity of  74.4 ± 1.2 %. We studied the state using entanglement witnesses, showed the violation of a bell inequality and verified its high entanglement persistency against photon loss.

Finally, we demonstrated a teleportation and an entanglement swapping experiment with a complete bell state analysis that was based on the controlled phase gate.