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[ANGLÈS] We have investigated a highly efficient source of polarization-entangled photons for long-distance free-space communication and other experiments involving significant propagation loss. The source is an evolution of the ’folded sandwich’. We have achieved an unprecedented detected pair rate of ∼ 1 million pairs/s per nm per mW of pump power combined with high quantum entanglement quality (fidelity with the ideal Bell state of 98.3% ± 0.4% and violation of CHSH’s inequality by more than 85 standard deviations in only 10 seconds for 10 uW of pump power).