| Quantum technology provides the possibility of breaking through the classical limit for communication,computing,imaging,metrology and other information processing,which is conducive to improve the information security,processing speed and measurement sensitivity.However,the quantum information processing is still in the principle demonstration stage up to now.In order to really apply the quantum technology in information processing,there are many technical bottlenecks and difficulties need to overcome.For example,further improving the quality of quantum source,improving the measurement system,and developing the novel information processing technology to satisfy the different requirements are all important.In this thesis,we propose a scheme based on cascaded optical parametric amplifier a nd s tudy o n both theoretical and experimental aspects to solve the problems of improving the quality of quantum source and overcoming the adverse effects of detection loss on quantum enhanced precise measurement.Firstly,the quantum characteristics of high-gain cascaded parametric amplifiers and their applications in quantum enhanced precision measurement and continuous variable entanglement measurement are studied.Then the output properties of low-gain cascaded parametric amplifiers and their applications in engineering the joint spectral function of photon pairs are analyzed.We also gener-ate the high-purity heralded single photon source and analyze the factors affecting the efficiency and purity of single photon.The major contents and innovations are as follows:?)We propose a cascaded parametric amplifier(nonlinear interferometer,NLI)to realize the measurement of multiple observables beyond the standard quantum limit for the first time.The dual-beam sensing NLI can further improve the signal-to-noise ratio of phase measurement,and has been experimentally verified by using fiber-based cascaded parametric amplifiers.We find the principle of quantum resource allocation– the resource can be allocated to a certain component to achieve optimal but not both together,and it is strictly proved according to Fisher information theory,which provides a basis for designing the optimal measurement scheme.?)For the current problems of measuring the continuous variable entangled state,the phase sensitive amplifier(PSA-)assisted balanced homodyne detectors is proposed.The advantages of this scheme include: the entanglement between two different types of entangled fields can be obtained by measuring any output field;it is insensitive to detection loss;it also has significant advantages under multi-temporal-mode conditions.So,this method is helpful for the development of practical quantum technology.We also make a verified experiment based on fiber system,and the measured inseparability of the entangled source is 4.6 d B,which is the best result in fiber system.?)We deeply study the method of engineering the joint spectral function of correlated photon pairs by cascaded parametric amplifier,including two-stage system and multi-stage system.A high-quality polarization entangled light source is produced by a two-stage scheme,and a heralded single-photon source(HSPS)is produced by a threestage scheme.The heralded efficiency is > 90%,the modal purity is over 0.95,and the center wavelength was flexibly adjustable.In addition,we also theoretically analyze the influence of inter-stage loss on spectrum engineering of cascaded amplifier,which provides a basis for the selection of nonlinear experimental systems and the parameter optimization. |
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