Waveguide source for an on-demand entanglement distribution network

Most quantum communication protocols rely on the distribution of entangled photon pairs. If the transmission channel is an optical fiber both photons should have a wavelength around 1550nm. We present a source of polarisation entanglement based on spontaneous parametric down-conversion (SPDC) at telecom wavelengths. Using fiber-pigtailed ppLN crystals we can profit from the clean χ
²
SPDC process, as opposed to four-wave mixing techniques, and also from a stable and efficient coupling to single mode fibers. Using a cw-pump, a tight energy correlation between the entangled photons is achieved. This fact is used here to distribute the entanglement through multiple channels employing only passive wavelength multiplexing. We demonstrate a possible application scenario with a single central source distributing entanglement to four users simultaneously. The source can also be used for creating tri-partite entanglement using the recently demonstrated cascaded SPDC scheme.