Theoretical And Experimental Investigation For Production Of Multiple Quantum Correlated Beams And Realization Of Phase Locking Using Four-wave Mixing Process Based On Atomic Ensembles

Multiple correlated beams,even multipartite entangled states are important not only for fun-damental tests of quantum effects but also for their numerous possible applications in quantum technologies.They are important research topics in quantum optics as well as atomic and molec-ular physics,at the same time,they are also indispensable investigation tools for studying these fields.Some quantum phenomenon,such as quantum nonlocality,and quantum entanglement both need multipartite entangled states.Consequently,the generation of multipartite entangled states has become an important topic in the field of quantum optics.This thesis includes the following four projects:(1)We investigate the experimental implementation of phase locking of the relative phase in a nonlinear interferometer using coherent modulation locking technique.We have two main nov-elties compared to the previous phase locking technique:(A)lock the relative phase between the three beams instead of two beams;(B)lock the internal phase of a nonlinear interferometer.(2)We investigate the possibility of an experimentally feasible cascaded four-wave mixing(FWM)system to generate tripartite entanglement.We verify that genuine tripartite entanglement is present in this system by calculating the covariances of three output beams and then considering the violations of the inequalities of the three-mode entanglement criteria,such as two-condition criterion,single-condition criterion,optimal single-condition criterion and the positivity under partial transposition(PPT)criterion.We also consider the possibilities of the bipartite entangle-ment of any pair of the three output beams using the Duan-Giedke-Cirac-Zoller criterion and PPT criterion.We find that the tripartite entanglement and the bipartite entanglement for the two pairs are present in the whole gain region.The entanglement characteristics under different entangle-ment criteria are also considered.Our results pave the way for the realization and application of multipartite entanglement based on the cascaded FWM processes..(3)We theoretically characterize the performance of the pairwise correlations(PCs)from mul-tiple quantum correlated beams based on the cascaded four-wave mixing(FWM)processes.The presence of the PCs with quantum correlation in these systems can be verified by calculating the degree of intensity difference squeezing for any pair of all the output fields.The quantum corre-lation characteristics of all the PCs under different cascaded schemes are also discussed in detail and the repulsion effect between PCs in these cascaded FWM processes is theoretically predicted.We also apply the theoretical predictions to the experimental data and find that the theoretical predictions agree with the measured results.Our results open the way for the classification and application of quantum states generated from the cascaded FWM processes.(4)we demonstrate the single-step fabrication of a multimode quantum resource from four-wave mixing(FWM)process in hot Rb vapor using for a spatially structured pump,which consists of a coherent combination of two tilted pump beams.During this FWM process,one probe beam is amplified,three conjugate and two new probe beams are generated.The measured degrees of the intensity squeezing for the four-beam case and six-beam case are around-4.1±0.1 dB and-4.7±0.1 dB,respectively.The generated multiple quantum correlated beams are naturally sepa-rated with distinct directions,which is crucial for sending them out to quantum nodes at different locations in quantum communication.Our scheme is compact,simple,phase insensitive,and easily scalable to larger number of quantum-correlated modes.