High-performance Single-photon Sources And Its Quantum Optical Properties

In this Thesis,based on self-assembled semiconductor quantum dot embedded in a micropillar cavity,we have studied and discussed high performance single-photon sources,and near Fourier transform limited single photons,quantum interference be-tween sunlight and quantum dot resonance fluorescence.Based on quantum dot embedded in a micropillar cavity,we have realized single-photon sources with the optimal overall performance around the world.An ideal single-photon source must be on-demand and simultaneously meet three crucial requirements:high extraction efficiency,high single-photon purity,and high indistinguishability.So far,these three quantities have never been achieved simultaneously in a single device.Here,by combining molecular beam epitaxy with lithography processes,we have ob-tained high-quality,tunable optical microcavities resonant with quantum dots' frequen-cies.With pulsed resonant fluorescence and Purcell enhancement techniques,we exper-imentally realized the "all-around" single-photon source with a Purcell factor of 6.2(1),extraction efficiency of-66%,single-photon purity of 99.1(1)%,and indistinguishabil?ity of 98.5(4)%.Immediately after achieving high performance single-photon sources,we further demonstrated that our device can generate near Fourier transform limited single photons.The high indistinguishability between single photons could maintain more than 14.73 ?s,which supports the studies of quantum information processing with>1 000 photons.Compared with the best single-photon sources based on spon-taneous parametric down-conversion,single-photon sources based on quantum dots are?10 times brighter,and the power of pump lasers they required are only at the level of nanowatts.We demonstrated Hong-Ou-Mandel interference,post-selective entanglement gen-eration,and quantum beat between sunlight and quantum dot resonance fluorescence.As we know,sunlight and quantum dot resonance fluorescence come from dissimilar sources,they are different in polarizations,spatial modes,spectral properties,tempo-ral properties,and also photon statistics.Previous works on quantum interference with dissimilar sources mostly concentrate on artificial sources at laboratorial scale.Here,we report an experiment on quantum interference with a natural source at astronomical scale.With techniques making the otherwise vastly different photons indistinguishable in all degrees of freedom,we observed two-photon Hong-Ou-Mandel interference with a raw visibility of 80(7)%.Then,by initialing two photons into orthogonal polarization,a post-selective two-photon entanglement can be generated.The fidelity of entangle-ment is 83(2)%,and the state violates the Bell inequality with the standard deviation of 3.13 times.Finally,with time-resolved measurement,a quantum beat at the detuning of 4 GHz has been achieved.The visibility still exceeds the classical limit even at the detuning?4 times of the linewidth,and decreases from unity as the detuning increases.All three aspects of the interferences violate the classical limit revealing the quantum nature of our experiment on two-photon interference between sunlight and quantum dot resonance fluorescence.Based on the state-of-the-art single-photon source,we have performed several quantum information processing experiments with linear optics.To this today,most of the existing works employ photonic qubits generated from spontaneous parametric down-conversion.An intrinsic noise of this kind of sources,however,is multiphoton emission.One must be set to low efficiency for detectors to overcome this problem,which imposes a large limit on its applications.Here,by actively demultiplexing single photons from high-performance quantum dot,we have prepared two important exam-ples of graph states-four-photon Greenberger-Home-Zeilinger state and cluster state with fidelities of 78.9(20)%and 75.8(7)%.Besides the preparation of graph states,we also perform a proof-of-principle demonstration of Shor's algorithm for factoring 15.The compiling technique used in this work reduces the resource requirement that enables to match four-photon cluster state,and the method used to extract the answers makes the quantum circuit to be more robust to noise.The successes of these novel works re-veal the quantum character of our experimental platforms,and open new routes towards quantum information processing with deterministic single-photon sources.