  Triggered sources of entangled photons play crucial roles in almost any
existing protocol of quantum information science. The possibility to generate
these non-classical states of light with high speed and using electrical pulses
could revolutionize the field. Entangled-light-emitting-diodes (ELEDs) based on
semiconductor quantum dots (QDs) are at present the only devices that can
address this task 5. However, ELEDs are plagued by a source of randomness that
hampers their practical exploitation in the foreseen applications: the very low
probability (~10-2) of finding QDs with sufficiently small
fine-structure-splitting for entangled-photon-generation. Here, we overcome
this hurdle by introducing the first strain-tunable ELEDs (S-ELEDs) that
exploit piezoelectric-induced strains to tune QDs for
entangled-photon-generation. We demonstrate that up to 30% of the QDs in
S-ELEDs emit polarization-entangled photon pairs with entanglement-fidelities
as high as f+ = 0.83(5). Driven at the highest operation speed of 400 MHz ever
reported so far, S-ELEDs emerge as unique devices for high-data rate
entangled-photon applications.
