Near Optimal Single Photon Source Based On Self-assembled Quantum Dot In A Micro Cavity

Self-assembled semiconductor quantum dots are artificial nano-particles made by molecular beam epitaxy technique,which can form discrete energy level structures just like a natural atom.Quantum dot is considered to be a promising single photon source for quantum information and optical quantum computing,because it relies on rapidly developing semiconductor fabrecation technologies.Quantum dots have been provid-ing the most state-of-the-art single photon source between all the quantum systems.Scalable photonic quantum technologies require single photon source with high levels of purity,indistinguishability,and efficiency simultaneously.Though the de-mands of purity and indistinguishability have been achieved through s-shell pulsed res-onant excitation,the efficiency reminds as low as few percent.For the further improve-ment of extraction efficiency,the coupling between QD and micro-cavity is strongly desired.Here we experimentally demonstrate a single quantum dot resonant with a micro-pillar cavity.With the enhancement of Purcell effect,the generatation of reso-nance fluorescence single photons have an extraction efficiency of 66%,single-photon purity of 99.1%,and photon indistinguishability of 98.5%.This is the first time that QD single photon source satisfied the high efficiency and near-perfect levels of purity and indistinguishabilty simultaneously and thus open the way to multi-photon experiments with QD single photon source.As for optical quantum computing,we successfully demonstrate boson sampling experiment with QD single photon source.Boson sampling is believed as a complex tasks that can be difficult for classical computers.Two completely different technical routes is applied.Firstly,a programmable time-bin encoded boson sampling machine is achieved with a loop-based architecture.This is the first time that QD single photon source served in boson sampling experiment,The observed sampling rates are more than 100 times faster than previous experiments based on parametric down-conversion source.Secondly,with the development of a 3D ultralow-loss optical circuits and high-speed active optical switches,We perform experiments with 20 single photons fed into a 60-mode interferometer.The corresponding sample spaces have a size up to 3.7×1014.Our experimental approach points out a way to the noisy intermediate-scale quantum regime through boson sampling.