Method and system for stabilization of a laser beam for an entangled photon source

A system for stabilization of a pump beam in an entangled photon source and for stabilization of the pump beam for the generation of entangled photons, comprising:

• a pump laser generating a polarized pump beam and;
• a source, whereby the source is arranged behind the pump laser and comprises a non-linear element for the generation of entangled photons;
• a polarizing monitoring means arranged between the pump laser and the source or behind the source, wherein the polarizing means comprises two output ports for splitting up the pump beam after the generation of the entangled photons into two part-pump beams with orthogonal polarizations;
• two detection means, arranged behind the two output ports of the polarizing monitoring means;
• and
• a control means for controlling the power or the polarization of the pump beam, wherein a control loop is formed by the pump laser as actuation means, or by one or more polarization adjustment means as actuation means, the polarizing monitoring means, the detection means, and the control means, whereby the polarization adjustment means is arranged between the pump laser and the source.