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Quantum key distribution (QKD) relying on single photons is regarded as one of the most mature quantum technologies.1,2 However, the impossibility of amplifying single photons sets restrictions on the transmission distance. Entanglement-based QKD schemes are able to overcome these range limitations when embedded in quantum networks,3,4 while also exhibiting a lower vulnerability to eavesdropping attacks.1,58 For both fiber-based9 and satellite-based10 quantum cryptography, the most prominent sources of entangled photon pairs to date are based on the spontaneous parametric downconversion (SPDC) process. These sources are commercially available and can be operated in a large temperature range.11 As a drawback, SPDC sources exhibit approximately Poissonian photon pair emission characteristics,12 which severely limits their brightness when a high degree of entanglement—and thus a low qubit error rate (QBER)—is demanded. The biexciton–exciton (XX-X) spontaneous decay cascade in epitaxially grown semiconductor quantum dots (QDs) has been demonstrated to be a viable alternative to SPDC sources due to the sub-Poissonian entangled photon pair emission statistics.13 In particular, GaAs QDs obtained by the Al droplet etching technique14 are capable of emitting polarization-entangled photon pairs with a fidelity to the $|ϕ+⟩$ Bell state beyond 0.98,15,16 owing to an intrinsically low exciton fine structure splitting (FSS),17 a low exciton lifetime of about 230 ps, and a near-zero multiphoton emission probability even at maximum brightness.18 This allowed the demonstration of entanglement-based QKD with a QBER as low as 1.9%.16,19