Preparation Of Entangled Photon Source And Its Application In Quantum Information

Quantum information science,as an emerging and cross-cutting subject,has developed a lot since its birth.It has effectively combined quantum mechanics and classical information science to achieve information beyond the classic coding,transmission,and calculation capabilities.Among them,the photon entangled state not only provides it with valuable resources as a core element,but also shows its unique advantages over other systems,including:the stability and ease of preparation of entangled photon sources;the use of photons as carriers to encode is difficult to interact with the environment,It has strong coherence;photons have good applicability,and most experimental operations can be completed at room temperature.Optical information processing is also one of the earliest physical experimental systems used for quantum communication and quantum computation.Based on this,this thesis mainly introduce the preparation of entangled photon pairs with high brightness through the parameter down conversion process experimentally using a linear optical platform,and introduces several commonly used experimental systems for preparing entangled photon states.Then using these entangled photon states to complete some research topics in quantum information and in quantum computing,the research results of this thesis are as follows:1.Demonstrates the use of error-rejection coding to achieve high-fidelity transmission of single photon qubit.we experimentally demonstrate a faithful single-photon qubits transmission using error-rejecting coding,resorting to neither ancillary photons nor entangled photon resources.Using unbalanced polarization interferometer,the polarization qubits are transferred into the state on time-bin degree of freedom.Additionally,the deterministic transmission of single photon quantum states can be achieved with high fidelity.The immunity of time-bin encoded qubits against collective noise paves the way to practical quantum error-correction and error-rejection in quantum information science.2.Experimental investigation of the quantum simulation in general PT-symmetric dynamics using a single-photon system.Various theoretical and experimental progress achieved in parity-time symmetry in modern quantum physics regime is the most important accomplishment and stimulates many new applications.Although parity-time symmetry has been explored in many quantum systems,its demonstration for quantum simulating in single-photon system remains elusive.Here,we experimentally demonstrate a general parity-time symmetric two-level dynamical evolution in a quantum computation frame using a single-photon system,with enlarging the system using ancillary qubits and encoding the subsystem under the non-Hermitian Hamiltonian with post-selection.The single-photon state(qubit)dynamic evolutions can be observed with a high fidelity when the successfully parity-time symmetrically evolved subspace is solely considered.Owing to the effectively operation of the dilation method,our work provides a route for further exploiting the exotic properties of parity-time symmetric Hamiltonian for quantum simulating and quantum computing.3.Utilizing the non-reciprocity of the microcavity-quantum dot system complete entanglement purification and concentration,and to achieve long-distance quantum repeater.Distribution of maximal entanglement is a key technique in long-distance quantum communication.In particular,the entanglement distribution with high fidelity relies on the efficient entanglement purification and concentration.Here in this study,we present a feasible approach to complete the entanglement purification and entanglement concentration for A-type three-level entangled quantum dots by using the whispering-gallery-mode microcavity and the quantum dot coupled system.Exploiting the input-output process of the probe light,we design a parity check gate which allows the quantum non-demolition measurement on the remote entangled quantum dots.Moreover,one can distill a high-fidelity entangled solid-state ensemble from a mixed entangled state or less entangled state ensemble non-locally.The proposed protocol exhibits the advantages of high fidelity which could be further applied to quantum repeaters and quantum information processing with the current experimental technologies.4.Two-dimensional quantum walk with infinite steps using cross-Kerr nonlinearity.A quantum walk is the quantum analog of the classical random walk,which provides a powerful tool for quantum computation and quantum simulation.However,the current experimental realization of the quantum walk based on photonic systems has been restricted to evolution in one dimension or small scale in two dimensions so far,and the growing demands cannot be fulfilled for further application of certain quantum computation tasks.Here,we theoretically propose a feasible scheme of a two-dimensional quantum walk with infinite steps by exploiting the orbital angular momentum of the photons and the phase information of the auxiliary coherent state induced by cross-Kerr nonlinearity.The numerical simulation shows that a proper parameter setting guarantees the walking for infinite steps in a two-dimensional grid with nearly 100%success probability.