André Strittmatter

Solid-state quantum light sources emitting triggered single photons or entangled photon pairs have the potential to boost the performance of quantum key distribution (QKD) systems. Proof-of-principle experiments affirmed these prospects, but further efforts are necessary to push this field beyond its current status. In this work, we report on tools for the performance optimization of QKD systems using single-photon sources (SPSs). For this purpose, we developed a basic QKD testbed comprising a triggered solid-state single-photon source and a receiver module designed for four-state polarization coding via the BB84 protocol. Exploiting temporal filtering of the signal acceptance time window in a two-dimensional parameter space we analyze the sifted key fraction and the quantum bit error ratio (QBER) expected in in full implementations of QKD. Furthermore, we demonstrate real-time security monitoring by analyzing the QBER and the photon statistics, in terms of g(2)(\tau), inside the quantum channel in real-time during the key distribution process. This is achieved by correlating the photon flux recorded at the four ports of our receiver. Our findings can be directly applied and extended for advanced schemes of quantum communication representing an important contribution towards the development of QKD-secured communication networks based on quantum light sources.