We present an all-optical method for synchronizing remote quantum network stations dedicated to the generation or the storage of photonic entanglement. We apply our method to the connection of two sources emitting pairs of photons at telecom wavelengths. Our experimental setup is based on a pulsed telecom fiber laser operating at 2.5 GHz that pumps, after frequency doubling, two nonlinear waveguide photon-pair sources. Our synchronization scheme is validated via the implementation of a two-photon interference experiment performed at the relay station, i.e. where the Bell state measurement takes place. We show a raw visibility greater than 90%, obtained in the 4-fold coincidence counts, for a separation distance of 100 km between the photon- pair sources. This result demonstrates the relevance of our approach.
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