Generation Of Tripartite Polarization Entangled States Of Light And Establishing Of Deterministic Quantum Entanglement Among Three Atomic Ensembles

Quantum networks have become an advanced topic in quantum information,recently.A practical quantum network usually includes quantum information transmission channels and quantum nodes.Light is an ideal carrier for the transmission of quantum information among quantum nodes.Thus the generation of non-classical states of light,which are able to interact with atoms,is a basic requirement for constructing quantum networks.Both the polarization of light and atomic spin are described by Stokes operators,and fluctuations of polarization variables can be easily mapped onto collective fluctuations of an atomic ensemble,thus the quantum states transfer between CV polarization states of light and spin states of atomic ensembles can be conveniently realized.Quantum repeaters are effective systems to extend quantum networks,in which stable and efficient quantum memories play key role.During my Ph D's study two research subjects are accomplished: the first,polarization squeezed and polarization entangled states of light were experimentally prepared,which provide efficient quantum resources for realizing interaction between light and atomic ensembles;the second,we demonstrated quantum mapping of entanglement between off-line prepared optical entangled states and three distant atomic ensembles and established entanglement of atomic spin-waves via electromagnetically-induced-transparency(EIT)light-matter interaction.Then the stored atomic entanglement was controllably transferred into a tripartite quadrature entangled states of light,which was space-separated and was dynamically allocated into three quantum channels for conveying quantum information.The main accomplished research works are as follows:1.The laser at 398 nm is generated by a cavity-enhanced frequency doubler,which is used as the pump source for preparing non-classical states of light at Rubidium atomic transition.The radial heat diffusion model is used to quantify the role of residual thermal effects firstly and 380 mW second harmonic light at 398 nm is obtained when the mode-matched input fundamental wave light power is 1W.2.A pair of quadrature amplitude squeezed optical fields are prepared from two degenerate optical parameter amplifiers,then the polarization squeezed state of light and bipartite polarization entangled state of light are generated by via linearly optical transformation on the polarizing beamsplitter networks,during which the phase differences between input beams have to be controlled very well.3.One quadrature phase squeezed state of light and two quadrature amplitude squeezed states of light are used to generate the tripartite quadrature entangled states of light at the frequency resonant with D1 line of Rubidium atoms.Then,the obtained tripartite quadrature entangled states are transformed into tripartite polarization entangled states by means of coupling their submodes with three strong coherent beams on an optical beam splitter network.4.A tripartite optical entangled state is transferred into three atomic ensembles located 2.6 meters apart from each other via EIT light-matter interaction and entanglement among three atomic ensembles are experimentally proved by measuring the released beams.The creative works are as follows:1.For the first time,we prepared the bright polarization squeezed states of light resonating with D1 Rubidium line,which is relatively convenient for directly homodyne detection,and thushas potential applications in the future quantum networks.2.We experimentally generated bipartite and tripartite polarization entangled states of light resonating with D1 Rubidium line,which provide effective resources for developing continuous variable quantum information networks.3.The off-line prepared multipartite entanglement of optical modes is mapped into three distant atomic ensembles to establish entanglement of atomic spin waves via EIT light-matter interaction,firstly.The existence of entanglement among released three optical modes verifies that the system has capacity of preserving multipartite entanglement.The presented protocol can be directly extended to larger quantum networks with more nodes.