  The generation of high-quality entangled photon pairs has been being a
long-sought goal in modern quantum communication and computation. To date, the
most widely-used entangled photon pairs are generated from spontaneous
parametric downconversion, a process that is intrinsically probabilistic and
thus relegated to a regime of low pair-generation rates. In contrast,
semiconductor quantum dots can generate triggered entangled photon pairs via a
cascaded radiative decay process, and do not suffer from any fundamental
trade-off between source brightness and multi-pair generation. However, a
source featuring simultaneously high photon-extraction efficiency, high-degree
of entanglement fidelity and photon indistinguishability has not yet been
reported. Here, we present an entangled photon pair source with high brightness
and indistinguishability by deterministically embedding GaAs quantum dots in
broadband photonic nanostructures that enable Purcell-enhanced emission. Our
source produces entangled photon pairs with a record pair collection
probability of up to 0.65(4) (single-photon extraction efficiency of 0.85(3)),
entanglement fidelity of 0.88(2), and indistinguishabilities of 0.901(3) and
0.903(3), which immediately creates opportunities for advancing quantum
photonic technologies.
