On-demand generation of indistinguishable polarization-entangled photon pairs

An on-demand source of indistinguishable and entangled photon pairs is a fundamental component for different quantum information applications such as optical quantum computing, quantum repeaters, quantum teleportation and quantum communication. Parametric down-conversion and four-wave mixing sources of entangled photons have shown high degrees of entanglement and indistinguishability but the probabilistic nature of their generation process also creates zero or multiple photon pairs following a Poissonian distribution. This limits their use in complex algorithms where many qubits and gate operations are required. Here we show simultaneously ultra-high purity (g^(2)(0) < 0.004), high entanglement fidelity (0.81 +/- 0.02), high two-photon interference non-post selective visibilities (0.86 +/- 0.03 and 0.71 +/- 0.04) and on-demand generation of polarization-entangled photon pairs from a single semiconductor quantum dot. Through a two-photon resonant excitation scheme, the biexciton population is deterministically prepared by a Pi-pulse. Applied on a quantum dot showing no exciton fine structure splitting, this results in the deterministic generation of indistinguishable entangled photon pairs.