Preparing the deployment of Quantum Key Distribution over a classical network infrastructure in Prague

Quantum Key Distribution (QKD) is a promising tool for secure communication in the near future. In combination with one-time-pad technique, it provides an unconditionally secure communication channel (meaning that it is secure against an adversary, even with unlimited computational power), at least in principle. However, a major implementation challenge for some schemes is the reliable creation, transportation, and measurement of entangled photon pairs over long-distance fiber networks. Our project aims to explore the possibilities for distributing quantum information on an existing network infrastructure while measuring the effects of real-world conditions. We characterized a commercial source of entangled photons. We measured its spectrum, brightness (1.6 +/- 0.3) x10(4) pairs/s/mu W, and performed quantum state tomography (QST) to reconstruct the density matrix of the quantum state. Our implementation focuses on an all-fiber solution, which would enable a simplified QKD implementation. In laboratory conditions, we achieved the visibility equal to (0.957 +/- 0.004) as a mean in both bases with a coincidence rate of (275 +/- 4) counts/s and successfully ran QKD protocol with secret key rate of (86 +/- 1) bits/s and average quantum bit error rate (QBER) of (4.8 +/- 0.7) %.