  The realization of single-electron sources in integer quantum Hall systems
has paved the way for exploring electronic quantum optics experiments in
solid-state devices. In this work, we characterize a single Kramers pair
emitter realized by a driven antidot embedded in a two-dimensional topological
insulator, where spin-momentum locked edge states can be exploited for
generating entanglement. Contrary to previous proposals, the antidot is coupled
to both edges of a quantum spin Hall bar, thus enabling this mesoscopic
capacitor to emit an entangled two-electron state. We study the concurrence
$\mathcal{C}$ of the emitted state and the efficiency $\mathcal{F}$ of its
emission as a function of the different spin-preserving and spin-flipping
tunnel couplings of the antidot with the edges. We show that the efficiency
remains very high ($\mathcal{F}\geq 50\%$) even for maximally entangled states
($\mathcal{C}=1$). We also discuss how the entanglement can be probed by means
of noise measurements and violation of the Clauser-Horne-Shimony-Holt
inequality.
