Experimental Investigation Of Quantum Correlation And Conical Emission Based On Four-wave Mixing In Atomic Ensembles

This thesis presents the experimental demonstration of an atomic source of narrowband non-classical states of light. Employing four-wave mixing in hot atomic rubidium vapor, the twin beams produced are naturally compatible with atomic transitions and may be employed in atom-based quantum communication protocols.We demonstrate the production of twin beam and analyze their quantum correlations between the two produced light beams. Using detector in each mode, we verify the production of twin beam light, achieving a reduction in intensity difference variance of7dB below the standard quantum limit. We get a series of pictures of conical emission and we experimentally study the spatial relationship between the quantum correlation and conical emission from FWM process in a rubidium atomic vapor. We measure the squeezing between the probe and the conjugate at different angle of the probe and the pump. Four-wave mixing(FWM) has long been known to have promising applications in quantum information and quantum communication.In conclusion, the production of twin beam light through four-wave mixing in an atomic vapor is a straightforward and powerful technique. The observation of strong squeezing in this system demonstrates its capability to push measurement boundaries. The near-resonant beams it produces combined with its inherently multi-mode nature makes it ideally suited for quantum imaging and quantum-information processing. It therefore provides an extremely versatile experimental technique for performing measurements beyond the shot noise level.This thesis is mainly divided into the following chapters: In the first chapter, the squeezed state is introduced. and it’s application prospect is stated.In the second chapter, we introduce the model of four-wave mixing process. And we deduce about the model of Kerr effect and self-focusing..In the third chapter, we introduce the design of our experiment and the devices.In the fourth chapter, we give the experimental results and analysis.In the last chapter, we give a conclusion of my thesis.