Generation And Measurement Of Continuous Variable Orbital Angular Momentum Entanglement

Propagating light beams carry spin angular momenta(SAM)associated with the polarizations and orbital angular momenta(OAM)related to the spatial helical phase structures.Recently,the quantum OAM states have attracted increasing attention because of added increases in dimensionality of the associated Hilbert space and their potentials for super-resolution quantum imaging,quantum metrology,and high-dimensional quantum information processing.The quantum OAM states can also be applied to measure the rotation angle of optical beams beyond the shot-noise limit(SNL).Another important application of the OAM states is their connectivity with atoms,allowing for transformation and storage of quantum information.Hyper-entanglement,simultaneously entangled with SAM and OAM,can be used to enhance channel capacity,and has great potentials in quantum super-dense coding,multi-channel quantum information transmission.In this thesis,we mainly studied on continuous variable(CV)squeezed and entangled states of orbital angular momentum.The main contents are as follows:1.We presented the model of a NOPO and studied the noise characteristics of NOPO with detunings,including bipartite and tripartite entanglement both below threshold and above threshold.2.We theoretically analysed and experimentally demonstrated the optimal pump mode for generation of the first order Hermite-Gauss mode HG10 mode entanglement by comparing with the other two pump modes,the results show that the maximum entanglement can be obtained with the optimal pump mode.3.We demonstrate experimentally a measurement scheme for the Stokes operators for the continuous-variable squeezed states of orbital angular momentum(OAM).An OAM squeezed state is generated by coupling a dim HG01-mode quadrature-squeezed light beam with a bright HG10-mode coherent light beam on a 98/2 beam splitter.Using an asymmetric Mach–Zehnder interferometer with an extra Dove prism in one arm,we measured the three orbital Stokes operators of the OAM squeezed states and finally characterized their positions and noise on the orbital Poincaré sphere.4.We experimentally generated a pair of entangled states for the first order Hermite-Gauss modes(HG10 entangled states and HG01 entangled states)using a single type-?OPO,and demonstrated that the entanglement is CV hyperentanglement which is simultaneously entangled with SAM and OAM,and finally characterized their positions and noise on both the spin Poincaré sphere and orbital Poincaré sphere.The creative works in this thesis are as follows:1.We experimentally demonstrated the optimal pump mode for generation of the first order Hermite-Gauss mode HG10 mode entanglement and show that the maximum entanglement can be obtained with the optimal pump mode.2.We demonstrate experimentally a measurement scheme for the Stokes operators for the continuous-variable squeezed states of orbital angular momentum(OAM).Using an asymmetric Mach–Zehnder interferometer with an extra Dove prism in one arm,we measured the three orbital Stokes operators of the OAM squeezed states and finally characterized their positions and noise on the orbital Poincaré sphere.3.We experimentally generated CV hyperentanglement with simultaneous entanglement of SAM and OAM using a type-?OPO and characterized their positions and noises on both spin and orbital Poincare spheres.