Research And Design Of Ion Trap And Fiber Microcavity Coupling System

Mature and reliable quantum networks enable functions such as efficient quantum computing and secure quantum communication.Quantum networks are usually composed of optical transmission links and quantum nodes.Optical transmission links can transmit photonic qubits,and quantum nodes can store,operate,and read qubits.The system with cold ions trapped in ion traps and interacting with optical resonators is one of the important means to realize reliable quantum nodes.The ion trap system can not only stably trap cold ions with long coherence time for a long time but also realize various complex quantum logic gates.The optical resonator provides a strong coupling between cold ions and cavity photons,and the photons radiated by the cold ions can be efficiently collected into the modes of the optical resonator by the Purcell effect.The microcavity structure with high fineness and small mode volume can support stronger coupling,but the resonator formed by the optical lens is difficult to achieve the optimal microcavity due to the influence of its size.In recent years,the optical Fabry-Perot microcavity has provided a novel scheme to achieve high fineness and small mode volume.It is challenging to construct a stable coupling system of the ion trap and the fiber microcavity.The ion trap size limits the fiber microcavity’s minimum cavity length.Therefore,it is necessary to design the structure of the fiber microcavity to achieve the optimal coupling between cold ions and cavity photons.In addition,the highly reflective dielectric film on the surface of the fiber microcavity will also affect the electrical potential of the ion trap.When the microcavity is too close to the ions,the ions cannot be stably bound in the cavity.The main purpose of this thesis is to design a novel coupling system of the ion trap and the fiber microcavity.The whole system needs to include a fiber cavity trap,an electric drive device,a mechanical support structure,and so on.The integration scheme of the ion trap and the fiber microcavity is realized by fabricating the fiber cavity by the process of photolithography and gold plating on the side and the end face of the fiber(fiber cavity mirror).The metal-coated fiber microcavity can transmit light and electric charge,and at the same time,the metal layer on the fiber end face can shield the electric charge on the highly reflective dielectric film.This system is designed to confine a single 138Ba+ ion and realize the coupling between the fiber microcavity and the ion energy level transition with the corresponding 493 nmwavelength.To efficiently collect photons,we perform a theoretical analysis of the overall system to achieve optimal coupling of individual parts.The optimized cavity-ion coupling parameters are(g,κ,γ)/2π=(65,167,20)MHz.The cavity length of the fiber microcavity is designed to be 250 μm.To improve the stability of the system,we also simulate and analyze the vibration,performance of the ion trap,thermal stability,etc.The main part of the system is composed of materials with similar thermal expansion coefficients,which increases thermal stability.The system’s isolation of internal and external vibration is realized using a spring connection.We solve the difficulties of manufacturing coupled systems at the theoretical level and have completed the verification of key technologies with the help of our team.The whole system can be expanded into a complex quantum network system to realize quantum computation and quantum communication.