Abstract

By now, free-space quantum key distribution (QKD) has seen many experiments validate the possibility of its implementation in various real world scenarios[1-4]. Recently, particular interest has focused on entanglement based QKD systems since they can tolerate higher channel losses than systems based on weak coherent laser pulses. However, while free-space channels offer tantalizing opportunities for QKD, such as using low earth orbit satellites for worldwide secure communication, only very recently has work by Semenov and Vogel [5,6] provided a theoretical foundation for the study of the transmission statistics and characteristics of free-space communication channels. In this submission, we study the influence of the turbulent atmosphere on entangled photon pairs where one photon from each pair is sent over a 1.3km free-space link. Using the system detailed in [3], with the recent update of a bright Sagnac interferometric entangled photon source[7], we study the effects of the turbulent atmosphere on the entangled properties of the photon pairs and the performance of the system using different pump rates and under various loss conditions. Already, we have been able to verify the theoretical prediction of Semenov and Vogel [5,6] that the transmission probability tends toward a log-normal distribution in highly turbulent and lossy experimental conditions as shown in Fig. 1.

© 2011 IEEE