  Transferring entangled states between photon pairs is essential for quantum
communication technologies. Semiconductor quantum dots are the most promising
candidate for generating polarization-entangled photons deterministically.
Recent improvements in photonic quality and brightness now make them suited for
complex quantum optical purposes in practical devices. Here we demonstrate for
the first time swapping of entangled states between two pairs of photons
emitted by a single quantum dot. A joint Bell measurement heralds the
successful generation of the Bell state $\Psi^+$ with a fidelity of up to $0.81
\pm 0.04$. The state's nonlocal nature is confirmed by violating the CHSH-Bell
inequality. Our photon source is compatible with atom-based quantum memories,
enabling implementation of hybrid quantum repeaters. This experiment thus is a
major step forward for semiconductor based quantum communication technologies.
