  Deterministic solid-state quantum light sources are considered key building
blocks for future communication networks. While several proof-of-principle
experiments of quantum communication using such sources have been realized,
most of them required large setups often involving liquid helium infrastructure
or bulky closed-cycle cryotechnology. In this work, we report on the first
quantum key distribution (QKD) testbed using a compact benchtop quantum dot
single-photon source operating at telecom wavelengths. The plug\&play device
emits single-photon pulses at O-band wavelengths ($1321\,$nm) and is based on a
directly fiber-pigtailed deterministically-fabricated quantum dot device
integrated into a compact Stirling cryocooler. The Stirling is housed in a
19-inch rack module including all accessories required for stand-alone
operation. Implemented in a simple QKD testbed emulating the BB84 protocol with
polarization coding, we achieve an antibunching of $g^{(2)}(0) = 0.10\pm0.01$
and a raw key rate of up to $(4.72\pm0.13)\,$kHz using an external pump laser.
In this setting, we further evaluate the performance of our source in terms of
the quantum bit error ratios, secure key rates, and tolerable losses expected
in full implementations of QKD also accounting for finite key size effects.
Furthermore, we investigate optimal settings for a two-dimensional temporal
acceptance window applied on receiver side, resulting in predicted tolerable
losses up to $23.19\,$dB. Not least, we compare our results with previous
proof-of-concept QKD experiments using quantum dot single-photon sources. Our
study represents an important step forward in the development of fiber-based
quantum-secured communication networks exploiting sub-Poissonian quantum light
sources.
