中性原子里德堡阻塞效应在量子信息中的应用

Neutral atoms trapped in optical lattice or optical tweezers and separated by few micrometers to tens of micrometers can interact with each other while they are excited to the Rydberg states with high principal quantum numbers. This phenomenon is named Rydberg blockade. Since the interatomic distance can be larger than the wavelength of visible light, it is able to realize individual control and readout of the quantum states for the interacting Rydberg atoms experimentally. There have been many applications of the Rydberg blockade effect in implementing quantum information processing and simulating many-body quantum dynamics in condensed matter physics. Recently, experimental demonstrations of the maximally entangled states and the quantum controlled NOT gate have been successfully completed with two neutral atoms via Rydberg blockade, however, the fidelity of the demonstrations are currently limited by many kinds of dissipation sources. Therefore, it is scientifically important to study the coherent coupling between Rydberg atoms and quantized light fields under the influence of dissipation and to study the applications of Rydberg blockade induced nonlinear optical effect. In this project, the nonlinear optical effects induced by Rydberg blockade will be studied and used for optical quantum computation. The hybrid system consists of interacting cold Rydberg atoms and cavity quantum electrodynamics will be studied as well, we aim to reveal the connections between photonic dynamics and Rydberg blockade effect and to propose experimentally feasible schemes for quantum information processing with dissipation being well suppressed. The results will be generalized to the hybrid system where Rydberg atoms and microwave photons in superconducting circuit are directly coupled.

囚禁在光晶格或光镊内的中性原子被激发到主量子数较高的里德堡能级后可以在几微米到十几微米距离范围内发生相互作用，即里德堡阻塞效应。由于原子间距大于可见光波长，因而实验上可以利用激光对单个里德堡原子进行独立控制并读取其量子态。里德堡阻塞效应在量子信息和凝聚态物理多体动力学的量子模拟中都有广泛应用。最近，人们利用该效应在实验上成功制备了两原子最大纠缠态和构建了两比特量子受控非门，但是在多种退相干机制的影响下，保真度仍然不高。因此，我们对在耗散影响下里德堡原子与量子化光场的相干耦合及里德堡阻塞诱导的非线性光学效应的应用展开研究具有重要的科学意义。我们将研究利用里德堡阻塞效应诱导的非线性光学效应实现光量子计算；研究里德堡原子和腔量子电动力学系统衔接的复合体系，阐述光子动力学与里德堡阻塞效应之间的联系，提出能有效抑制耗散的量子信息处理方案，为里德堡原子与超导电路微波光子直接耦合系统的研究提供理论参考。

高激发里德堡态具有寿命长、偶极矩大和电极化率大等优点，这使得里德堡原子可以在几微米到十几微米距离范围内发生偶极－偶极或范德瓦尔斯长距离相互作用，这种效应在量子信息和凝聚态物理多体动力学的量子模拟中都有广泛应用。在本项目中，基于冷原子间的里德堡－里德堡相互作用，我们研究了囚禁在耦合腔中的里德堡原子与光场相互作用后的量子动力学，该物理系统还可以用于实现量子非线性吸收滤波器；提出了囚禁在光晶格中的里德堡原子的量子隐型传态，其优点在于：量子比特的纠缠态容易制备；贝尔基矢态的测量只需通过单比特操作实现，且无需精确控制里德堡相互作用强度，该方案有望用于实现可扩展量子计算；研究了激光独立操控的两个四能级里德堡原子在范德瓦尔斯相互作用影响下的电磁诱导透明（EIT）现象；提出利用非线性极化模型模拟激光弱驱动下均匀耦合里德堡原子系统的激发动力学，该模型可以在保留原子间关联的条件下解析计算系统处于稳态时的激发数统计特性，为在实验上测量该驱动－耗散系统的量子关联特征提供有效依据。此外，在交叉领域，我们研究了两个弱相互作用谐振子在耦合强度随时间变化条件下的纠缠动力学；研究了量子比特－谐振子超强耦合系统在绝热近似条件下的量子动力学以及反转对称性破缺对基态特性的影响；我们还提出在超导磁通比特与微波共面波导谐振腔的耦合系统中，通过操纵量子热库制备相位可控的任意轨道态等。