Measurement Of High-order Moments And Variances For Light Field

Quantum measurement is one of fundamental problems in quantum mechanics.It plays an very important role on studies of quantum theory and their applications such as quantum computation and quantum communication.Usually,one concerns with quantum nondemolition (QND)measurements which are complicated since a complete measurement needs to reconstruct quantum states of the measured system.Typically,a complete state reconstruction with standard techniques demand great experimental efforts,is strongly affected by decoherence mechanisms,and,frequently,the obtained information exceeds our requirements.However,in some cases we need not know the complete information of the system under consideration,and one only wants to extract partial information of the considered system.In these cases,techniques for extracting efficiently the required partial information are most welcomed and even necessary.The problem is even harder when the field is not directly accessible and a quantum probe has to be used for the purposes of an indirect measurement. Therefore,in recent years much attention has been paid to non-complete quantum measurement which is also regarded as instantaneous measurement.In this thesis,An instantaneous measurement scheme is proposed to measure indirectly higher-order moments and variances for light field.In this scheme,two-level atoms are used to act as quantum probes,and we make use of multi-photon Jaynes-Cummings type interactions between light field and probe atoms.The mean values of the field operators connect with observables of the probe atoms through integral transformations.All relevant information of the higher-order moments and variances for light field is contained in derivatives of the probe atoms at the initial time.The thesis is divided into six chapters.Chapter 1 is devoted to an introduction.Chapter 2 is intended as an overview of the basic concepts and techniques used in the remainder of this thesis.In Chapter 3,measurement of theκth-power amplitude squeezing of a cavity field is investigated.It is shown that theκth-power amplitude squeezing of the cavity field can be obtained by detecting population of atoms in terms of aκ-photon and a 2κ-photon Jaynes-Cummings models.In Chapter 4,we investigate measurement of higher-order photon number and its fluctuation using two-level probe atoms.In chapter 5,we show how to detect higher-order correlation functions of the light field.A summary and an outlook of this thesis are given in the last chapter.