  Mutually entangled multi-photon states are at the heart of all-optical
quantum technologies. While impressive progresses have been reported in the
generation of such quantum light states using free space apparatus,
high-fidelity high-rate on-chip entanglement generation is crucial for future
scalability. In this work, we use a bright quantum-dot based single-photon
source to demonstrate the high fidelity generation of 4-photon
Greenberg-Horne-Zeilinger (GHZ) states with a low-loss reconfigurable glass
photonic circuit. We reconstruct the density matrix of the generated states
using full quantum-state tomography reaching an experimental fidelity to the
target $|{\text{GHZ}_4}\rangle$ of $\mathcal{F}_{\text{GHZ}_4}
(86.0\pm0.4)\,\%$, and a purity of
$\mathcal{P}_{\text{GHZ}_4}=(76.3\pm0.6)\,\%$. The entanglement of the
generated states is certified with a semi device-independent approach through
the violation of a Bell-like inequality by more than 39 standard deviations.
Finally, we carry out a four-partite quantum secret sharing protocol on-chip
where a regulator shares with three interlocutors a sifted key with up to 1978
bits, achieving a qubit-error rate of $10.87\,\%$. These results establish that
the quantum-dot technology combined with glass photonic circuitry for
entanglement generation on chip offers a viable path for intermediate scale
quantum computation and communication.
