  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 show that temporal filtering of single-photon pulses enables a
performance optimization of QKD systems implemented with realistic quantum
light sources, both in experiment and simulations. To this end, we analyze the
influence of temporal filtering of sub-Poissonian single-photon pulses on the
expected secret key fraction, the quantum bit error ratio, and the tolerable
channel losses. 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. Furthermore, we
demonstrate real-time security monitoring by analyzing the photon statistics,
in terms of $g^{(2)}(0)$, inside the quantum channel by correlating the photon
flux recorded at the four ports of our receiver. Our findings are useful for
the certification of QKD and can be applied and further extended for the
optimization of various implementations of quantum communication based on
sub-Poissonian quantum light sources, including measurement-device-independent
schemes of QKD as well as quantum repeaters. Our work represents an important
contribution towards the development of QKD-secured communication networks
based on quantum light sources.
