Squeezing In Quantum Optics

Quantum optics is a subject in studying the coherence and the quantum statistical properties of radiation field, as well as the quantum characters of light interacting with matter. The research has showed that some quantum efFects have appeared in the interaction of light with atoms, especially in the nonlinear process. There are three main non-classical features for quantum field, i.e. photon anti-bunching effect, sub-Poissonian statistics distribution, and squeezing effects. These features not only benefit our further understanding of nature of light, but also have significant applications in the optical field. In particular, squeezing effects, due to the quantum fluctuation of one quadrature phase smaller than that in coherent state, can be used in optical communication and other fields. Therefore, the study on squeezing phenomena is an important topic in quantum optics.The theoretical development and experimental realization of atomic squeezing is one of the greatest progresses in optical and atomic optics. Squeezing efFects of the atom, one very important quantum effect in its interaction with light have also attracted much attention due to its significance in decreasing the quantum noise caused by atomic movement.In this thesis, we have studied the field and atomic squeezing, and proposed some new kinds of squeezing and investigated their effects. The other quantum properties of the field and atom have also been discussed. The major content ofthis thesis is displayed as follows:1. We first introduced the development and the theory of the squeezed state in the field and the atom.2. On the basis of single mode superposition states, the squeezing and quantum statistical properties in the two-mode superposition states have been studied. The influences of the photon number, photon number difference, coefficients in the states and their relative phase on these non-classical properties have also been discussed. We have compared the results in the two-mode superposition states with those in the single-mode case.3. By investigating the two-atom dipole amplitude-squared squeezing and two-mode second-power :H -squeezing in a system of a two-mode vacuum field interacting with two coupled atoms, the influences of the initial atomic coherence and dipole-dipole interaction on the two types of squeezing have been discussed. The relation between the two types of squeezing has also been revealed.4. The dipole squeezing of a A-type three-level atom interacting with a strong coherent field in a high-Q Kerr Cavity is investigated. The effects of the Kerr medium, the field-atom coupling coefficient and the detuning on the atomic dipole squeezing are discussed by numerical calculation.5. Based on the group-theoretical structure for the density-dependent multi-photon Jaynes-Cummings model, we have constructed the dressed SU(2) coherent state. The atom and field squeezing and the anti-bunching effect for the system evolving from the dressed SU(2) coherent state have been studied.In conclusion, we have discovered some new field and atomic squeezing in different systems, proposed a new kind of quantum state and discussed photon anti-bunching effect, sub-Poissonian statistics distribution.