超级里德伯原子间的稳态关联集体激发与量子纠缠

Correlated collective excitation and quantum entanglement between two Rydberg superatoms in steady state

处于同一偶极阻塞区域的里德伯原子系综可以看作一个超级原子,如果它们被捕获在两个不同的光偶极阱中,那么每一个光偶极阱中的子原子系综可以看作为一个亚超级原子.由于这两个亚超级原子共享不超过一个激发的里德伯原子,所以它们会强烈地关联起来.本文研究这两个里德伯亚超级原子的稳态关联集体激发特性和量子纠缠行为.结果表明原子数目带来的影响非常明显:里德伯亚超级原子越大(包含原子数目越多),集体激发概率越大;最大纠缠只发生在等大的两个里德伯亚超级原子之间.通过增加原子数目,可以实现介观领域的量子纠缠,对量子-经典对应的研究以及量子信息处理有着重要的作用.

Owing to the unique physical characteristics of Rydberg atoms,which play an important role in quantum information and quantum computation,the theoretical and applied research of Rydberg atoms have become the hot spots of scientific research in recent years.With the large polarizability of Rydberg atoms,even a small electric field could cause a considerable electric dipole moment,resulting in a strong dipole-dipole interaction between Rydberg atoms.The multiple excitations of the Rydberg states are strongly inhibited because of the strong dipole interaction between atoms within a mesoscopic interaction(blockade)region.We call this phenomenon the dipole blockade effect.The dipole blockade effect makes it possible to build single-photon quantum devices,implement quantum gates,generate quantum entanglement,and simulate many-body quantum problems,etc.A Rydberg atomic ensemble in the same blockade region can be regarded as a superatom.In the same way,if these atoms trapped in two optical dipole traps,each sub-ensemble can be considered as a sub-superatom which is closely related to the superatom.According to the fact that two Rydberg sub-superatoms can be strongly correlated due to sharing no more than one excited Rydberg atom,we study correlated collective excitation and quantum entanglement between two Rydberg sub-superatoms in a steady state.With the superatom model,the problem of exponentially increasing system size with the number of atoms can be circumvented to a certain extent in studying many-body physics.By solving the two-body Lindblad’s master equation accurately,we obtain the analytical expressions for the collective excitation probabilities of the two sub-superatoms,and the concurrence measuring the bipartite entanglement between them.Our results show that they are all sensitive to the number of atoms in each Rydberg superatom:the bigger(including more atoms)the Rydberg superatom,the higher the collective Rydberg excitation probability is.And that the maximally entangled state can only be obtained with two equal-sized Rydberg superatoms.When this condition is fulfilled,the mesoscopic entanglement can be generated by adding the number of atoms in each Rydberg superatom.This may provide an attractive platform for studying the quantum-classical correspondence and have potential promising applications in quantum information processing.