Generating Multimode Quantum Correlation By Using Spatial Multiplexing In Four-wave Mixing

In recent years,with the rapid development of quantum communication and quantum information processing,it has led to more and more in-depth research on the correlation in quantum systems.Quantum correlation and entanglement are nonlocal correlation and can exist between systems that are far apart and do not interact with each other.This makes quantum correlation and entanglement a non-classical important resource,which is of great significance in quantum communication and quantum information processing.This thesis will introduce the following four work about the generation of multi-mode quantum correlation in four-wave mixing process by using spatial multiplexing.Firstly,generation of multipartite entanglement and correlated beams is of great significance to quantum communication and quantum network.We use a semiconductor laser as our light source,and generate the quadruple quantum correlated beams from four-wave mixing process in rubidium atomic vapor cell by using spatial multiplexing.According to our proposed scheme,not only can the number of generated quantum correlated beams increases exponentially(2n,n is the number of rubidium vapor cell),but also the quantum correlation increases as the number of quantum-correlated beams increases.We experimentally verify that when n = 2 by using the spatial multiplexing in four-wave mixing(FWM)process we produce quadruple quantum correlated beams and measure the quantum correlation(intensity difference compression)from a single FWM process at-5.6 dB and-6.5 dB increased to-8.2 dB from cascaded FWM process.Secondly,the strength of quantum correlation between multipartite quantum correlated beams directly affects its application in quantum communication and quantum information processing.The strength of quantum correlation generated from our system is affected by different parameters.We adjust the main parameters in the system,such as changing single photon detuning,two-photon detuning,rubidium cell temperature,pump power and gains,to study the quantum correlation between the quadruple beams and either pair of beams by changing the parameters,so that we find the optimal parameters range to produce the quantum correlation.Thirdly,the multi-mode quantum correlation has important applications in quantum information processing and quantum communication.We use the "conical pump beam + Gaussian mode probe beam" optical system in FWM process to produce a conical conjugate beam.We experimentally measured the quantum correlation between the probe and conical conjugate beam and the intensity difference-squeezing is about-3.8 dB.The multimode nature of quantum correlations and the dependent of quantum correlation on different parameters are also studied.Fourthly,we produce the conical probe beam and conical conjugate beam from FWM process by using the spatial multiplexing and the "conical pump beam + conical probe beam" optical system.We experimentally measured the quantum correlation between the conical probe and conical conjugate beam and the intensity-difference squeezing is about-2.6 dB.The multimode nature of quantum correlations and the dependent of quantum correlation on different parameters are also studied.