Experimental Construction Of Quantum Network Based On Four-wave Mixing Process

Quantum is one of the important concepts in modern physics.It was first proposed by famous physicists Max Karl Ernst Ludwig Planck at the beginning of last century.In physics,a quantum is the minimum amount of any physical entity involved in an interaction,which is the foundations of bringing physics from the macro world to the micro world.Quantum mechanics and quantum optics have become important research fields of modern physics.My main research direction during my Ph.D.is to generate quantum resources such as quantum correlated beams and quantum entangled beams through nonlinear optical processes based on the atomic ensemble.Quantum resources have been widely used in quantum key distribution(QKD),quantum teleportation,quantum computation and quantum metrology.At present,the platforms that can generate quantum resources include optical,superconducting processes,ion traps and ultracold atoms.Each direction has its own unique advantages and application prospects.In recent years,quantum optical has drawn more and more attention due to its long coherent time,simple operation,good compatibility with integrated optics and good expansibility.In recent years,four-wave mixing(FWM)has been proved to be one of the effective methods to generate quantum correlated beams and quantum entangled beams.In this thesis,we mainly introduce the quantum network generated by FWM process.This thesis will introduce in details as following:1.We theoretically and experimentally characterize the performance of the pairwise correlations from triple quantum correlated beams based on the cascaded FWM processes.The pairwise correlations between any two of the beams are theoretically calculated and experimentally measured.Moreover,we also study the effects of the system parameters(the system gain)on the pairwise correlations.Our results provide a new way to analyze the internal structure of multipartite quantum correlated beams.2.We have experimentally constructed a spatially structured pump beam.Under this configuration,seven nonlinear optical processes can be integrated in the same vapor cell.Using these seven nonlinear processes,hexapartite entangled beams are generated.Because quantum entanglement is fragile and easy to interact with the external environment,we simulate three scenarios that may be encountered in practical applications,and study the influence of loss on hexapartite entanglement in detail.Our results are expected to have potential applications in the implementation of complex quantum information tasks.3.We innovatively combine spatial pump shaping(SPS)technology with optical orbital angular momentum(OAM)multiplexing technology.In the experiment,we first use SPS technology to integrate seven FWM processes in the same vapor cell,we could deterministically generate a continuous variable(CV)hexapartite entanglement.Then,in order to largely increase the scale of the prepared hexapartite entanglement,we utilize the OAM multiplexing technology.Consequently,we can deterministically implement a large-scale multipartite entanglement by simultaneously generating 11 channels of hexapartite entangled states over 66 OAM modes.At the same time,the quantum entanglement detection scheme based on Laguerre-Gauss mode is used to experimentally verify the quantum entanglement characteristics between these corresponding modes.In addition,because the optical OAM coherent superposition mode is beneficial to quantum communication in turbulent environments,we also study the multipartite entanglement characteristics of three coherent OAM superposition modes,and demonstrate the rich entanglement structure of the system in many aspects.These results suggest that our method can greatly expand the scale of multipartite entanglement and provide a new perspective and platform to construct CV quantum network.