  Quantum cryptography harnesses quantum light, in particular single photons,
to provide security guarantees that cannot be reached by classical means. For
each cryptographic task, the security feature of interest is directly related
to the photons' non-classical properties. Quantum dot-based single-photon
sources are remarkable candidates, as they can in principle emit
deterministically, with high brightness and low multiphoton contribution. Here,
we show that these sources provide additional security benefits, thanks to the
tunability of coherence in the emitted photon-number states. We identify the
optimal optical pumping scheme for the main quantum-cryptographic primitives,
and benchmark their performance with respect to Poisson-distributed sources
such as attenuated laser states and down-conversion sources. In particular, we
elaborate on the advantage of using phonon-assisted and two-photon excitation
rather than resonant excitation for quantum key distribution and other
primitives. The presented results will guide future developments in solid-state
and quantum information science for photon sources that are tailored to quantum
communication tasks.
