A Compact Source for Polarization Entangled Photon Pairs

Quantum cryptography the first technology in the area of quantum information that is in the process of making the transition from purely fundamental scientific research to an industrial application. The project described here represents an important step towards a prototype of a marketable quantum cryptography system, that is currently being developed in acollaboration effort of the Institute of Experimental Physics at the University of Vienna and Seibersdorf Research GmbH. My task in this project was the design and construction of a company source for polarization-entangled photon pairs. The one year period of the work described here covered the development of an initial proof of principle experiment for laser diode pumped source, a follow-up experiment, lab tests and a final test in an outdoor Bell inequality experiment. The results detailed here indicate the feasibility of incorporating this source into a prototype for a commercial quantum cryptography system. Furthermore, this source has been used to demonstrate the transmission of polarization-entangled photon pairs through 600m of atmosphere. This new method of distributing entanglement, might eventually overcome the limitations of the current fiber based systems and open new possibilities for quantum communication.