冷原子量子比特体系的新型构筑和操控方法的研究

近年来，中性冷原子量子比特体系已经在量子计算和量子模拟领域取得了一系列重要成果，本项目计划深入研究该体系中的量子比特构筑、量子态的纠缠和量子门的操控技术与方案等方面的重要科学问题。目前该体系面临的瓶颈与挑战包括提高两比特量子受控非门保真度，改善其量子比特物理架构对于原子里德堡态的相容性，增强量子比特内态的读出效率和建立可靠的原子-光子量子接口等重要问题。针对这些问题，本项目将从基于里德堡阻塞效应的两比特量子逻辑门，蓝失谐魔幻波长光势阱，快速且无损的量子比特测量以及基于光学谐振腔的原子-光子量子接口等四个具体方向分别开展新方案的理论设计与计算仿真。本项目预期获得的重要结果和关键数据包括：(1) 针对双光子激发过程，设计基于里德堡阻塞效应的新型高保真度两比特量子逻辑门方案，仅需对两束激发光之一按照特定波形进行幅度调制即可实现，并且能有效压制实验中多种典型退相干因素对保真度的不利影响；(2) 根据能同时对基态和里德堡态原子进行稳定囚禁的目标，求解满足双重魔幻条件的蓝失谐光势阱的相关参数；(3) 结合光抽运、循环跃迁以及与布居数快速转移相关的量子调控方法，发展快速、无损、低加热和高保真度的冷原子量子比特内态读取技术；(4) 运用Rb-Cs混合体系，通过Rb-Rb同种原子、Rb-Cs异种原子之间的里德堡阻塞效应，结合光学腔内的单光子态与冷原子系综的相互作用，设计针对冷原子阵列的原子-光子量子接口方案。同时，本项目将注重理论与实验的结合，通过在冷原子系综和单原子等物理系统中开展相应的基础性实验工作，以验证新方案的合理性并明确其优势。本项目有望运用当前相关领域快速进步的时机获得突破性研究进展，并将为中性冷原子量子比特体系下一阶段的发展提供有力支撑。

In recent years, the neutral cold atom qubit platform has made many important achievements in the areas of quantum computation and quantum simulation, and this proposed project plans to carry out in-depth research of the construction of qubit system, the entanglement properties of quantum states, and control technologies and protocols of quantum logic gates associated with the neutral atom qubit platform. Right now, this platform faces many bottlenecks and challenges, such as increasing the fidelity of the two-qubit quantum Controlled-NOT gate, improving the coherence between ground states and Rydberg states of the atomic qubits within the physical platform of optical dipole traps, enhancing the efficiency of qubit states readout process and establishing a reliable atom-photon quantum interface. With respect to these important issues, the proposed project will design new protocols and carry out the associated theoretical analysis and numerical simulations for the following directions: two-qubit quantum logic gates based on the Rydberg blockade effect, blue-detuned magic optical traps, nearly lossless measurement of qubit states and atom-photon quantum interface based on intra-cavity Rydberg blockaded atomic ensemble. The anticipated essential progress and key data include the following: (1) Design the off-resonant modulated driving waveform with respect to the two-photon ground-Rydberg transition for two-qubit controlled-phase gate; (2) Calculate the parameters to realize stable optical confinement of both the ground and Rydberg states while satisfying the doubly magic condition; (3) Develop fast, nearly lossless, low heating and high fidelity qubit readout method; (4) Obtain atom-photon quantum interface method based on the intracavity cold atom hybrid system with the presence of Rydberg blockade, which will specifically focus on the atom-photon gate with cold atom array. Meanwhile, this proposed project will pay special attention to the harmonic integration of experiment and theory, and in particular, it will carry out fundamental experiment tests in cold single-atom and atomic ensemble systems to verify the new designs and elaborate the advantages. The research of this proposed project will utilize the chances of rapid developments in relevant scientific areas and try to make breakthroughs. It is anticipated that this proposed project will provide essential help to the development of neutral atom qubit platform.