基于里德伯超级原子快速制备三粒子单重态

Fast generation of three-atom singlet state with Rydberg superatom

量子纠缠是量子信息处理和量子计算的基本资源,简单而高效地制备纠缠态始终是学者们研究的热点问题之一.作为量子信息编码理想载体之一的中性里德伯原子,以其独特的优势在纠缠态制备领域占有一席之地.本文将四能级倒“Y”型结构的里德伯原子系综放置于里德伯阻塞球内部使之形成超级原子,在弱腔场近似下将量子信息编码在超级原子的有效能级上,结合量子Zeno动力学和绝热捷径的方法,简单有效地制备了三粒子单重态.此外,本方案考虑了退相干因素(包括腔的衰减和超级原子的自发辐射)对单重态保真度的影响.数值模拟结果表明,本方案不需要对系统演化时间进行精确的控制就可以得到很高的保真度,并且单重态的保真度对退相干因素是比较鲁棒的.

Quantum entanglement is a basic resource of quantum information processing and quantum computation.The simple and efficient generation of entangled states is always one of the hot research topics. As one of the ideal carriers of quantum information encoding, neutral Rydberg atom occupies a place in the field of generation of entangled state with its unique advantages. For example, Rydberg atom has a large volume and is easily ionized by an external electric field, so it is very sensitive to the change in the external electric field. Therefore,the interaction strength between Rydberg atoms can be changed by altering the external electric field. Rydberg state is a highly excited state, but its radiation attenuation is very small: the radiation lifetime can reach a millisecond level or even longer. The distance between the atomic kernel and the outermost electron is relatively long, and the electric dipole moment is very large. In this paper, the four-level inverted " Y"-type Rydberg atomic system is introduced into the Rydberg blocking ball to form a superatom, and the quantum information is encoded on the effective energy level of the superatom under the condition of weak cavity field. We construct shortcuts to adiabatic passage in a three-superatom system. Combined with quantum Zeno dynamics and shortcuts to adiabatic passage, the three-particle singlet state is simply and effectively generated. In addition,the influence of decoherence factors(including cavity decay and spontaneous emission of superatoms) on the fidelity is considered in this scheme. Numerical simulation results show that the proposed scheme can obtain high fidelity without precisely controlling the evolution time, and the fidelity of singlet state is robust to decoherence factors, since no cavity-photon population is involved in the whole process because of the quantum Zeno dynamics.