Theoretical Investigation On Linear Quantum Manipulation Of Four-wave Mixing Process In Rubidium Vapor

Quantum states of optical field,such as squeezing state and entangled state,are essential resources in fundamental research of quantum science and applications range from quantum information to quantum metrology.With the advancement of quantum science,it is necessary to realize the manipulation of quantum states in order to complete more complex research work.Based on four-wave mixing(FWM)process in rubidium vapor,we construct different system by introducing the linear beam splitter and theoretically study the quantum states manipulation under various parameters.There are four main parts included in this thesis:(1).A coherent feedback control on four-wave mixing process system is constructed by introducing a beam splitter.With different transmittance of beam splitter,gain of FWM process and feedback phases,we investigate how these parameters will influence the intensity squeezing of the output beams.Besides,we also study how these parameters will influence the bipartite entanglement of the system by applying two kinds of criteria,Duan-Giedke-Cirac-Zoller(DGCZ)criterion and the positivity under partial transposition(PPT)criterion.(2).We apply the coherent feedback control structure to the nonlinear SU(1,1)interferometer based on four-wave mixing processes.With the conservation of photon number in the interferometer,we investigate how will the feedback parameters will influence the phase sensitivity of the coherent feedback controlled SU(1,1)interferometer.We find that the phase sensitivity can be manipulate by adjusting feedback parameters and the phase sensitivity of the interferometer can be enhanced under certain condition.(3).Based on the theoretical study of the multipartite entanglement generated by the cascaded four-wave mixing processes,we simulate the unavoidable optical losses in real experimental implementation by using beam splitter introducing vacuum fluctuation.Then by changing the transmittance of beam splitters,we can manipulate the losses on the system and study how different loss rates will affect the entangled range and entanglement degree in tripartite entanglement and quadripartite entanglement in cascaded four-wave mixing processes.In addition,we study the subsystems' entanglement of tripartite and quadripartite entanglement at different loss rates.