![]() The atom-atom CV entanglement has been generated by means of QND interaction and dissipative mechanism28,29, respectively. Another approach of generating atom-atom entanglement is DLCZ (Duan, Lukin, Cirac and Zoller) scheme, which is based on entanglement between light and atoms as well as single photon probabilistic counting26'27. BS: beam splitter BHD1 (2): balanced homodyne detector RF Coil: radio frequency coil.Ītom-atom entanglement has been realized by mapping entangled photons into two sets of trapped atomic ensembles25. Schematic of atom-atom entanglement generation system. Correspondence and requests for materials should beįigure 1. University, Taiyuan, 030006, People's Republic of China. 2Collaborative Innovation Center of Extreme Optics, Shanxi In DV regimeġState Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan, 030006, People's Republic of China. Quantum nodes play the role of quantum repeater, and the entanglement among different nodes has to be required for constructing large-scale quantum networks and transferring quantum states. ![]() et al.24 have introduced the concept of quantum repeater to overcome this problem24. In practical applications of quantum information, the inevitable transmission loss limits the communication distance. The information transfer from one atomic node to another node has been realized as well19,23. With the help of entanglement of light and atoms, the teleportation from photonic quantum bits and optical quantum modes to atomic spin wave states have been experimentally achieved, respectively18,22. The schemes of producing CV entanglement between light and atoms via three-wave or four-wave mixing have been proposed20,21. The CV entanglement of light and atomic ensembles has also been obtained by means of quantum non-demolition (QND) interaction18,19. The Spontaneous Raman Scattering (SRS) process has been used to generate DV entanglement between single photons and atoms15-17. Besides cavity quantum electromagnetic dynamics system in which the interaction of light and atoms is enhanced by optical cavity, atomic ensembles are the proper quantum nodes as a result of high optical density13,14. The entanglement of light and atoms is utilized to transfer quantum information between different quantum systems. Meanwhile atomic ensembles are one of the promising candidates for quantum nodes to process and memory quantum information1. Light is the best quantum information carrier and is used as quantum channels in quantum networks, usually. With the development of quantum information, quantum network consisting of quantum channels and quantum nodes have attracted more and more attentions. Entanglement swapping can entangle two quantum systems that have never directly interacted with each other, and thus is a significant protocol in quantum communication6-8. The discrete-variable (DV) entanglement of single photons and the continuous-variable (CV) entanglement of optical modes have been deeply studied2'3 and applied in a variety of quantum information protocols, such as quantum teleportation, quantum entanglement swapping, quantum secret sharing, quantum computing, and so on4-12. It is crucial to establish entanglement between remote nodes with stationary quantum systems in a quantum network1. Finally, the established entanglement between two macroscopic atomic ensembles is verified by the inseparability criterion of correlation variances between two anti-Stokes optical beams respectively coming from the two atomic ensembles. Then, the entanglement swapping is unconditionally implemented between the two prepared quantum systems by means of the balanced homodyne detection of light and the feedback of the measured results. Each of two stationary atomic ensembles placed at two remote nodes in a quantum network is prepared to a mixed entangled state of light and atoms respectively. Here we propose a scheme of deterministically entangling two remote atomic ensembles via continuous-variable entanglement swapping between two independent quantum systems involving light and atoms. Entanglement swapping can entangle two spatially separated quantum systems without direct interaction. Yanhong Liu1, Zhihui Yan1,2, Xiaojun Jia1,2 & Changde Xie1,2Įntanglement of two distant macroscopic objects is a key element for implementing large-scale quantum networks consisting of quantum channels and quantum nodes. Received: 05 March 2016 Accepted: 21 April 2016 Published: ĭeterministically Entangling Two Remote Atomic Ensembles via Light-Atom Mixed Entanglement Swapping ![]()
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