Research On Ingaas Based Single Photon Detector And Bragg-Reflection-Waveguide Entangled Photon Sources

As the great development of quantum information technology,China has built a quantum network over 2000 kilometers and launched a quantum satellite.In the early of this year 2018,Google announced that they have successfully developed a 72-qubit quantum computer.This is not the end of the quantum information technology,but it is a start.Quantum communication integrated on the cell phone is still not achieved,quantum supremacy is still on the way and there is still a lot of work to do to make the quantum computer widely access to the public people.The poor performance of devices is one of the many reasons.The entangled photon sources and single photon detectors are the two key devices among many others.Single photon detectors are necessary to quantum communication and optic quantum computer,while entangled photon sources are necessary to quantum repeater and optic quantum computer.The performance of the individual devices would directly affect the system's performance.Integrated entangled photon sources promise many advantages,including scalable,easily reconfigurable architectures,small system footprint and the interfacing with CMOS electronics.In this thesis,our work mainly contains two parts,i.e.research of integrated entangled photon sources and research of single photon detectors.Our contributions are list as below:1,We designed an optimized Bragg-reflection waveguides(BRWs)and simulated it's performance on two quantum optic tasks.A semi-automatic algorism is used to solve the eigenmode of the simplified one dimensional BRWs.By this the type of the phasematching processes,the mode profiles at the phasematching wavelengths,their dispersion characteristics or the overlap integrals are achieved.The random optimization and simulated annealing method are used to optimize the parameter of the BRWs.After the one dimensional design,we used a two dimensional solver(COMSOL)to simulate the BRWs in two dimension and then we analyzed the performance of the designed BRWs in some quantum optic tasks.2,We designed and accomplished an experiment of time-bin entanglement.We tested the performance of the parametric down conversion of the BRWs.By taking advantage of pulsed state preparation and efficient free-running single-photon detection we drive our source at low pump powers,which results in a strong photon-pair correlation.It shows that the coincidence to accident ratio(CAR)reaches as high as 9260 ± 150.Then we conducted the time-bin experiment using the photons created from parametric down conversion.The tomographic reconstruction of the state's density matrix reveals that our source exhibits a high degree of entanglement.We extract a concurrence of 88.9 ± 1.8%and a fidelity of 94.2 ± 0.9% with respect to a Bell state.3,We designed a InGaAs/InP single photon detector with tunable gate frequency.Instead of restricting the spike noise by self-differencing or filtering method,we use an analog-to-digital converter(ADC)to sample the output voltage of the APD.Through the sampled voltage we can discriminate an avalanche signal from the noise.This method makes the continuous tuning of the gate frequency possible.We did experiment in both room temperature and low temperature conditions.The results show that the performance of our detector is comparable to the one using self-differencing or filtering method.The continuous tuning of the gate frequency would make it suitable for practice using and commercialize.