| Quantum entanglement is one of the most fundamental properties of quantum mechanics and the most important resources in quantum communications and quantum information. Thanks to a well-established quantum entanglement source, quantum information processing and quantum communication have been rapidly developing in recent years and many quantum protocols, such as quantum teleportation, quantum dense coding, or quantum cryptography, have been successfully implemented in lab tests. For long-distance quantum communication and quantum information processing network, quantum information needs to be transferred among quantum nodes and quantum channels with different characteristic frequencies. To realize a high fidelity teleportation between the nodes and faithful storing and retrieval of quantum states on demand, entangled states with balanced quantum correlation in both amplitude and phase quadratures are desired.In this thesis, the core objective of the job is to prepare a two-color continuous-variable entanglement states at 0.8 ?m (Rb-87 D1 line) and 1.5?m (lowest loss band of telecom optical fibers) wavelength, which will be an ideal candidate for the development of quantum communication and quantum information processing.The thesis is organized as follows:a. A full solid laser with output wavelength at 526.5 nm was devised and prepared, quantum noise characteristics of whose down-converted fields are measured. To realize continuous tuning of the frequency, a LiTaO3 electronic optical crystal is inserted in the laser cavity and the cavity length is adjusted. The laser frequency has been continuously tuned over 12 GHz at last.b. An above-threshold OPO based on PPKTP nonlinear crystal is pumped by the homemade 526.5 nm laser and generates two color continuous-variable entanglement states at 0.8 ?m and 1.5 ?m. The effect of the detuned narrow bandwidth analysis cavity on rotation of noise ellipse of optical fields is analyzed theoretically. Analysis cavities are designed and built to measure the phase quadrature noise characteristics of the down-converted fields. At the same time, accurate control of DROPO output wavelength is realized by adjusting several parameters of the OPO.c. A model of dual-end pumped OPO/OPA is proposed, which comebines the best characteristics of OPO and OPA. The generated intense down-converted fields by the OPO afford the injected seed beams of the OPA and local oscillators for the homodyne detection of OPA down-converted fields.d. The classical output characteristics and the down-converted fields quantum correlation properties of the OPA with injected signal are analyzed theoretically. And intense two color entangled beams with balanced quadrature correlations are generated by a combined OPO/phase-insensitive OPA device. Saturated absorption spectrum of hyperfine level transition for Rb D1 line is observed by using the 795 nm idler field. Meanwhile, long distance entanglement distribution was fulfilled via a 5 km optical fibre.Innovations in this thesis are:a. An all-solid Nd:YLF/LBO laser is developed. Output power of 770mW has been achieved at 526.5 nm.b. Using the homemade laser at 526.5 nm, we pump second order nonlinear process and generate intense two color continuous variable entanglement states at 1560 nm and 795 nm.c. Dual-end pumped OPO/OPA device is proposed which combines the advantages of OPO and OPA and can be used to generate entangled beams with large frequency difference and balanced quantum correlation for both quadratures.d. Phase-insensitive OPA/OPO combined device is developed, and this scheme effectively enhances the stability of the entanglement source and offers a method to prepare compact, efficient and stable two color entanglement resource.e. Continuous frequency tuning of the entanglement resource output is attained and the wavelength of the idler field has been precisely controlled to Rb-87 D1 line. At the same time, long distance continuous variable entanglement distribution has been realized via a 5 km optical fiber. |
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