Yang Xihua, Xiao Min
Department of Physics, Shanghai University, Shanghai 200444, China.
National Laboratory of Solid State Microstructures and School of Physics, Nanjing University, Nanjing 210093, China.
Sci Rep. 2015 Aug 28;5:13609. doi: 10.1038/srep13609.
Quantum entanglement provides an essential resource for quantum computation, quantum communication, and quantum network. How to conveniently and efficiently produce entanglement between bright light beams presents a challenging task to build realistic quantum information processing networks. Here, we present an efficient and convenient way to realize a novel quantum phenomenon, named electromagnetically induced entanglement, in the conventional Λ-type three-level atomic system driven by a strong pump field and a relatively weak probe field. Nearly perfect entanglement between the two fields can be achieved with a low coherence decay rate between the two lower levels, high pump-field intensity, and large optical depth of the atomic ensemble. The physical origin is quantum coherence between the lower doublet produced by the pump and probe fields, similar to the well-known electromagnetically induced transparency. This method would greatly facilitate the generation of nondegenerate narrow-band continuous-variable entanglement between bright light beams by using only coherent laser fields, and may find potential and broad applications in realistic quantum information processing.
量子纠缠为量子计算、量子通信和量子网络提供了一种重要资源。如何方便高效地在明亮光束之间产生纠缠，是构建实际量子信息处理网络面临的一项具有挑战性的任务。在此，我们提出了一种高效便捷的方法，在由强泵浦场和相对较弱探测场驱动的传统Λ型三能级原子系统中，实现一种名为电磁诱导纠缠的新型量子现象。通过两个较低能级之间低的相干衰减率、高泵浦场强度和原子系综的大光学深度，可以实现两个场之间近乎完美的纠缠。其物理根源是泵浦场和探测场产生的较低双重态之间的量子相干，类似于著名的电磁诱导透明。该方法仅使用相干激光场就能极大地促进明亮光束之间非简并窄带连续变量纠缠的产生，并可能在实际量子信息处理中找到潜在的广泛应用。
