Experimental Study Of Quantum Light Source And Multiphoton Interference Based On Self-assembled Semiconductor Quantum Dots

As an important physical carrier for quantum information processing today,pho-tons are also one of the first physical systems developed in the 1990s.However,the experimental studies of multiphoton interference and entanglement for more than 20 years are almost all based on the photon pair source of spontaneous parametric down-conversion(SPDC),which is essentially a probabilistic process.This kind of light sources have inevitably many pairs emission in each pulse pump,and the probabil-ity of generation is less than 10%,which greatly limits the scalability of multiphoton experiments based on them.The entanglement operation of 12 photons and 18 qubits is almost close to the upper limit number that can be achieved in reality as so far.Self-assembled semiconductor quantum dots,as a kind of "artificial atoms",have band structures similar to crystals and anharmonic discrete energy levels similar to nat-ural atoms.The internal exciton states are excited and then radiate,it is essentially a deterministic process.Deterministic single-photon source(SPS),entangled photon pair source(EPRS),multi-photon cluster state source,etc.can be achieved by deter-ministically pumping quantum dots to an excited state by light pulses and then sponta-neously radiating.Through proper pumping methods and coupling with proper micro-nano structures,the efficiency,purity,indistinguishability,and entanglement fidelity of the photons radiated by these light sources can all be close to ideal in theory.It is under this background that this paper uses pulse resonance excitation and self-assembled semiconductor quantum dots coupled with a micro-cavity to achieve a de-terministic single-photon source and entangled photon pair source with high efficiency,high purity,high indistinguishability and high fidelity.And using this single-photon source,a deterministic light source,the experimental research of multi-photon entan-glement and a heralded photon entangling gate was carried out.The details are as fol-lows:1.This article analyzes the basic principles and difficulties of using quantum dots to generate high-quality single-photon sources.It also introduces a experimental work of generation high quality SPS using resonance pulse laser to excite semiconductor quantum dots which weakly coupled with a micro-pillar cavity.When SPS's collec-tion efficiency is as high as 66%,it has 99.1%purity and 98.5%indistinguishability.And the two photons within the emission time interval of up to 14.7?s can still maintain the indistinguishability higher than 90%.This opened the way for the development of multi-photon experimental research based on deterministic single-photon sources.2.This article analyzes the basic principles and limitations of using quantum dots to generate high-quality entangled photon pairs.It also introduces a work of generation EPRS using two-photon resonance pulse to excite semiconductor quantum dots that are weakly coupled to a circular Bragg cavity(CBG).Its generation efficiency of a single photon pair reaches 0.59,and also has a fidelity of 0.9,a collection efficiency of 0.62,and a biexciton photon's indistinguishability of 0.9.3.Using the high-quality single-photon source developed in 1.,combined with fast and deterministic photonic switches,we demultiplex the SPS in a single spatial mode into multi SPSs which are identical,time synchronized and in different spatial modes.And using these SPSs,the four-photon Greenberger-Horne-Zeilinger(GHZ)state and linear cluster state multi-photon preparation experiments were carried out for the first time.The state preparation yield of?13Hz was obtained,and the fidelity of four-photon GHZ and cluster states were 0.790(0.009)and 0.763(0.004),respectively.4.Using the multiple SPSs developed in 3.,we demonstrated an experiment of two single-photon-assisted heralded two-photon C-NOT gate,and used this entangling gate to prepare heralded Bell entangled photon pairs.The obtained entangling gate operation's fidelity is 0.878(0.012),the operation rate is about 85/min,and the heralded efficiency is 0.8%.Among them,the operation rate and heralded efficiency are at least one order of magnitude higher than the similar type of experimennt.