Atomic Coherent States And Applications In Quantum Metrology

With the rapidly development of quantum information in recent years, people have a higher demand for the accuracy of measurement. In the usual classical setting, because of the limitation of classical light, the accuracy of the phase estimation can only meet the shot-noise limit which cannot meet the degree that people expected today. For this reason, the theory of quantum metrology based on quantum mechanics has been introduced. Quantum metrology is a subject about measurement and statistical inference, it has been widely used in gravitational wave detection, quantum lithography, biological sensing and many other related aspects because of its advanced accuracy.In this thesis, we main discuss the accuracy of phase measurements in the quantum metrology.With the atomic coherent states and particle number states as the input states of the MZI for the first time, we do some research including the photon number distribution and the average of the parity operator. The contents of this paper are listed below:In the first chapter, we mainly give the related introduction about quantum metrology. In the second chapter, we give the detailed introduction on MZI that commonly be used for quantum metrology, including its structure and operating principle. What’s more, in this chapter, we also give the probable factors influencing the accuracy of measurements in the quantum metrology, and give some explanation on phase detection method.In the third chapter, we firstly make a brief introduction of the origin and development of atomic coherent states, providing the HPR form. At the same time, we discuss the joint photon-number distribution after the input state entering the beam splitter, when taking the atomic coherent state and the quantum number state as the input states of the beam splitter. By analyzing the relationship between the photon-number distribution and the parameters of the quantum states,we inform that the increasing particle number or the increasing total angular momentum quantum number can lead to enhanced resolution and the improvement of precision of the phase measurements.In the fourth chapter, we detect output states through the measurement of parity operator detection on just one of the output beams of the MZI. Calculate the average ?? ?b?? of the parity operator, and then give the graphs on the change of ?? ?b?? with the varying parameter in the quantum states. Through the analysis of the graphs, we draw the conclusion: the injection of photon-number states along with atomic coherent states into the MZI apparently leads to enhanced resolution and the improvement of precision of the phase measurements with the increasing particlenumber or the increasing total angular momentum quantum number.