| Optical superlattice (OSL) is an important functional micro-structure material, which is known as quasi-phase-matching material (QPM) or nonlinear photonic crystal (NPC). It has already been widely applied in the field of nonlinear optics such as the frequency conversion of the laser. Nowadays people turn to explore the applications of optical superlattice in the field of quantum optics. Via micro-structure modulation, OSLs exhibit multiple novel functions in the engineering of quantum light sources. The inherent integration function of OSL materials fit the requirements of the practical applications in quantum information processing. We can obtain entangled photons from an OSL quantum chip, which becomes a new hotspot in the field of quantum optics. In this thesis, we comprehensively studied the compact manipulation of entangled photons by different ferroelectric domain modulation structures in the one-dimensional (1D) and two-dimensional (2D) OSL materials. Based on the principle of multiple QPM, photonic frequency, polarization, path entanglement and even hyper-entanglement can be directly generated under multiple concurrent spontaneous parametric down-conversion (SPDC) processes in OSLs. We study the entanglement properties of the compact photon pairs generated from OSL and their applications in quantum information processing. The main contributions are listed as follows:1. We proposed a scheme for the preparation of an integrated "beam-like" polarization entangled two-photon state by using2D OSL materials. By using an external polarizing beam splitter, degenerate and non-degenerate polarization entangled photon pairs with well-defined spatial mode can be directly obtained by a pair of mirror-symmetrical non-collinear QPM SPDC processes from2D OSL. Furthermore, considering the SPDC processes pumped by ultra-short femtosecond pulse, we can effectively obtain multiphoton polarization-entangled GHZ state and cluster state. Such photonic polarization entangled states have many advantages such as high efficiency, easy to collect, integrated, stable and portable since multiple QPM processes can effectively reduce the external discrete optical elements.2. We proposed a scheme for the preparation of the heralded single-photon multipartite entangled W state by using multiple QPM based on OSLs. OSLs act like natural coherent beam-splitters. When multiple QPM processes share the same mode of idler photon, it is possible to design the corresponding signal photon to locate coherently in different spatial modes. By triggering idler photon, the single-photon multipartite entangled W state is heralded and directly obtained. The arbitrary N-mode entangled W state can be produced via arranging domain structures in series. We calculated the concurrence and theoretically characterized the single-photon entanglement. We also discussed the experimental feasibility for the preparation of the single-photon multipartite entangled W state. Although the single-photon multipartite entanglement can be generated equivalently by multiple beamsplitters, our integrated realization of single-photon multipartite entanglement has many advantages, such as stability, high degree of entanglement, miniaturization, scalability. It has many important applications in quantum information processing, such as realizing entanglement distribution among different quantum memories in the quantum internet.3. We designed OSLs to enable the photon pairs from SPDC processes to be entangled over several degrees of freedom, achieving the hyper-entanglement. We proposed a compact generation of polarization-frequency hyperentangled photon-pair source by engineering a multi-stripe dual-periodic poled OSL. Each stripe is designed for the generation of a non-degenerate cross-polarization entanglement. The frequency of photon pair from each stripe differs, thus resulting in a high dimensional frequency-entanglement. We analyzed the temperature detuning character, the generation rate and the entanglement degree of the hyper-entangled state. Furthermore, we proposed another feasible experimental realization of such hyper-entangled source based on guided-wave optics which improves the performance with high brightness, miniaturization and stabilization. It is a very effective method for integrated engineering of hyper-entanglement with QPM technique based on OSL.4. We adopt the new types of entangled photon sources generated from OSLs to be applied in the fields of quantum information. We proposed a scheme for quantum assisted cloning based on single-photon entangled states. We can realize entanglement distribution of the quantum memories by using the single-photon multipartite mode-entangled W state in quantum networks. We proposed two protocols about quantum secure direct communication based on three-dimensional hyper-entangled states, which provided as the theoretical basis for the realization of a more efficient and safer quantum cryptography communication. Both single-photon multipartite mode-entangled state and two-photon hyper-entangled state can carry more quantum information and complete the task of multi-photon entanglement in quantum information processing, which will find very important applications in the future practical quantum information processing and quantum communications. |
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