Abstract

In quantum cryptography networks photons play an important role as flying qubits. Many schemes for the implementation of such quantum cryptography systems require non classical photon states, i.e. single photons or photon pairs [1]. Photon pair sources are well–suited due to their capability to create entangled photons with respect to polarization, time–energy or time–bin in a relative simple way. If it is necessary to establish a long distance communication between remote nodes, it is advisable to send the photons via optical fiber links. Thus the photons should either be in the telecom O-band around 1310 nm, which shows the lowest dispersion in standard optical fibers, or in the telecom C-band around 1550 nm, where they experience the lowest absorption. Therefore, a light source which creates photon pairs at telecom wavelengths is required for long–range quantum cryptography applications as mentioned above. Furthermore, in combination with erbium–doped fiber quantum memories for telecom wavelengths [2], it is even possible to implement completely fiber–based quantum repeaters. Hence it should be possible to share entanglement over large distances, which is a basic operation in quantum networks.

© 2015 IEEE