Abstract
The thesis is to study the quantum properties of optical fields, squeezing and entanglement, based on the electromagnetically induced transparency (EIT) schemes. Under the low-intensity approximation, we study the quantum entanglement between two fields after travelling through a Lambda-type EIT medium, and find that some particular conditions satisfies non-separable criterion. Extending the single-Lambda EIT system to multi-Lambda EIT system, one has more degree freedom to study quantum properties of light. By controlling the relative strengths among coupling fields, we find that the quantum properties of output fields can be changed if the input fields are non-classical light. Besides, the quantum nature of interacting fields can be thoroughly changed via cross phase modulation (XPM) nonlinear interactions, which depends on some controllable physical quantities. EIT is a quantum interference phenomenon that is caused by the interaction between light field and atomic levels. Some novel effects such as reduction of absorption and slow light can be arisen due to the atomic coherence induced by the interacting fields. Accordingly, based on the common atomic coherence in multi-Lambda EIT systems (double- and triple-Lambda EIT system), the non-classical effects of fields can be generated and manipulated by means of some classical manners. The interacting time between two light pulses can be greatly increased by the slow light effect in EIT system, and therefore the nonlinear interaction by the XPM term could be enhanced so that the quantum properties of individual fields or that between two fields can be generated from initial input classical fields. By investigating the quantum properties of interacting fields in these EIT-based systems theoretically, we obtain some results quantitatively, providing a further understanding about atom-field interaction processes. Furthermore, we expect that the results of the thesis can contribute to the field of quantum information science.