Research On Pump Space Mode And Generation Of Continuous-Variable Multimode Entanglement

Continuous variable quantum entanglement is one of the important resources in quantum optics.It has the quantum correlation property that classical light field does not have.And now It has been widely used in many fields,such as quantum communication,quantum metrology and quantum computing.The spatial modes of the light field,such as the Hermite mode and the Laguerre mode,have a complex spatial distribution.Therefore,the continuous variable multimode entangled state based on this spatial mode has attracted a lot of research interest.By using this spatial multimode entangled state as a quantum channel,parallel transmission and processing of information can be realized,and channel capacity and quantum computing speed can be improved.In addition,this multimode entangled state can be applied to the field of super-resolution quantum imaging to improve the image imaging quality,as well as the measurement accuracy in the field of quantum precision measurement such as displacement tilt angle.It has important application value.In this thesis,we theoretically and experimentally study entangle enhancement of continuous variables multimode entanglement based on pump space manipulation.The main contents are as follows:1?we theoretically analyzed the relationship of the pump and the two down-conversion modes and the effect of different pump modes on the inseparability.And we find that the optimal pump mode is the superposition ofLG₀⁰ andLG₁⁰ mode.However,the optimal pump mode is rather complicated and difficult to experimentally generate,the alternative scheme is using LG₁⁰ mode as the pump field to obtain the optimal entanglement.In the experiment,the LG₀⁰ mode or LG₁⁰ mode was used as the pump field to drive the non-degenerate optical parametric amplifier operating in spatial multimode.Then the hyperentanglement in orbital angular momentum and spin angular momentum was produced.The experimental results show that the enhancement for the inseparability of orbital angular momentum and spin angular momentum entanglement respectively was achieved usingLG₁⁰ mode.2?We theoretically analyzed how to produce quadripartite cluster states using a single multimode resonant optical parametric amplifier.Experimentally we also verify and measure for four-partite cluster states.In addition,the entanglement of the cluster states is improved by optimizing the pump mode.Compared with the preparation of multipartite entanglement by coupling the several squeezed state light field in the beam splitting,this device is more concise.