Quantum Clock Synchronization And Quantum Coherent Control

The process of spontaneous parametric down-conversion involves sending a pump laser beam into a nonlinear material. Occasionally, the nonlinear interaction inside the crystal leads to the annihilation of a high frequency pump photon and the creation of two lower frequency photons named as signal and idler. The two photons are entangled. People just take advantage of entangled photo pairs whose quantum correlation characteristic achieves the high accuracy measurement for space-time. Based on second-order correlation principle, we describe a measurement method of the distant clock synchronization analytically, which is achieved by the entangled photon pairs produced with spontaneous-Ⅱparametric down-conversion. This method can not only be used in studding the distant clock synchronization and the quantum positioning, but is useful in measuring the time difference of a pair of entangled photon passing the nonlinear crystal. The results show that the shorter the time difference is, the better the coherence and synchronization of the two probed events are.The entangled photon pairs propagation in space is studied by spontaneous parametric down-conversion, which is closely correlative with second-order correlation function. This is a two-photon process. In the study of the interaction process of light and atom, physical process of the two-photon excitation is also involved. Therefore, action process of controllable chirped pulse light field and two-photon process in two levels atomic system is studied in this paper. In term of Fresnel Zone Plate theory, how to carry out focusing effect of excited-state population and focusing effect of sum frequency would be discussed. The results show that two-photon process in under action of the chirped pulse light field; the focusing effect in two-photon transitions process and sum frequency process is achieved by cutting light field. We mainly use square pulse as the example to discuss physical method in this process. Focusing effect can be realized by this method for Gaussian pulse under two-photon absorption and nonlinear optical effect in the parametric process. The paper could be divided into five parts.Part oneIn this part, it mainly introduces the fundamental theories, including the concept and mathematical reasoning of full Quantization theory, second-order correlation function, spontaneous parametric down conversion and two-photon transition principle. It is the theoretical foundation of this paper. Part twoIn this part, it mainly describes specific principles and mathematical reasoning of theⅡtype optical parametric down conversion, which help the understanding of physics meaning of each expression.Part threeIn this part, it proposes a method of quantum entangled and squeezed light. Comparing with classic methods, the application of quantum method can improve the accuracy and the specific improved numerical value can be deduced.Part fourIn this part, the quantum measurement of the distant clock synchronization would be studied. The usage of quantum characteristic of entangled photon pairs enables the researcher to gain the higher accuracy than that of Classic measurement. The time difference is femtosecond order, which improve the accuracy. Based on the quantum feature of the entangled photon pairs produced with the spontaneous parametric down-conversion and the quantum coherent principle, the method of the distant clock synchronization is studied. The results show that the core method of the distant clock synchronization described in this paper is also the same with quantum positioning and measurement the time difference of a pair of entangled photon passing the nonlinear crystal. The results show that the shorter the time difference is, the better the cohence and synchronization of the two events probed are.Part fiveIn this part, it gives two-photon transition phenomenon in the process of the interaction of the chirped pulse and two-level system. Analytic representations of excited-state position probability would be obtained by using second-order perturbation theory. In term of Fresnel Zone Plate theory, how to carry out focusing effect of excited-state population would be discussed, as well as the second-order nonlinear optical sum frequency problems.