基于原子与原子和原子与光子相互作用体系的单量子态实验研究

The preparation, storage, manipulation, and detection of single quantum states constitutes the most fundamental aspects of quantum information applications, where each of the above aspects encompasses many basics physics and technological problems. Due to their exceptional coherence properties and demonstrated controllability, atoms are widely considered as among the most competitive qubit candidates, with photons naturally take the role of qubit state messengers. Within atomic systems, quantum degenerate ultracold atoms, cold atoms, and even room temperature atoms, can all be used in close connection with single quantum state research. In this proposal, we will study the generation of single excitation atomic quantum states and entangled photon pairs from cold atomic gas ensembles. We will characterize their properties, and develop appropriate applications. To enhance the efficiency and quality of single photon and single excitation atomic quantum states, we will explore highly excited Rydberg atoms, which even at room temperature can induce large electric dipole moment when placed inside crossed electric and magnetic fields. The increased dipolar interaction can aid in the conversion between photonic single quantum states as well as their manipulations. To further scale up multiparticle entanglement, we plan to study lattice systems loaded with ultracold atoms. We will control their ground state collisions and excited state Rydberg dipolar interactions to entangle atoms from different lattice sites. Our study will cover a wide temperature regime, employing a variety of atomic gas ensembles with interactions of different strength, to collectively understand their common features and analogous physical mechanisms governing single excitation atomic states and photonic states, to demonstrate and to further explore their applications to quantum information science.

单量子态的制备、存储、操控与探测是量子信息应用的基础，包含诸多基本物理问题和技术。原子拥有很好的相干性和易操控性，被认为是量子比特的最好载体之一，而光子由于其独有的特性则扮演量子信使的角色。与单量子态研究密切相关的原子体系包含了量子简并的超冷原子、冷原子和室温下的原子。我们拟研究冷原子系综的单激发量子态及纠缠光子对的产生、特性和应用；为提升单光子和单激发量子态的产生效率和质量，我们探索室温下外场中的高激发里德堡大偶极态，增强原子原子偶极相互作用强度，并利用原子原子偶极相互作用实现光子光子之间的相互作用转化与控制；为进一步提升多粒子纠缠态的可升级性，我们基于光晶格中的超冷原子，利用可控的碰撞相互作用和高激发里德堡原子的偶极相互作用，实现不同晶格点原子的纠缠。这些研究将从不同温度、不同相互作用强度以及不同原子系综揭示原子和光子单量子态的共同或类似物理机制，演示并拓展其在量子信息技术上的应用。

高效的量子信息处理和量子计算需要不同物理载体上单量子态之间的信息转移和传输。我们通过在不同的温度区间、不同的相互作用强度下，演示了基于原子和光子体系的单量子态的产生与调控。在实验上我们首次实现了利用波色凝聚体中原子自旋交换相互作用制备双数态，并利用磁场调控的 Feshbach 共振技术能够有效地、甚至任意地改变原子间的相互作用性质和强度。 这使得冷原子量子气体成为研究量子模拟最广泛的实验平台之一。理论上研究了里德堡原子的偶极特性，并在实验上实现了里德堡原子偶极量子态的动力学调控与检测。在实验上实现了冷原子超流到Mott绝缘态的相变，在光晶格体系中制备和测量了600对超冷原子纠缠对，并进一步实现了二维四体环交换相互作用及于此相关的任意子激发特性，这是量子计算和量子模拟领域重要的研究进展。