Entanglement with negative Wigner function of three thousand atoms heralded by one photon

8th Symposium on Frequency Standards and Metrology 2015

McConnell, Robert^1 ; Zhang, Hao^1 ; Hu, Jiazhong^1 ; uk, Senka^1,2 ; Vuleti, Vladan^1

Department of Physics, MIT-Harvard Center for Ultracold Atoms, Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge

MA

02139, United States^1

Institute of Physics, University of Belgrade, Pregrevica 118, Belgrade

11080, Serbia^2

关键词: Atomic ensemble;    Entangled atoms;    Quantum Computing;    Quantum Information;    Quantum metrology;    Spin distribution;    Technical improvement;    Wigner functions;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/723/1/012054/pdf
DOI  :  10.1088/1742-6596/723/1/012054

来源: IOP

【 摘 要 】

Quantum-mechanically correlated (entangled) states of many particles are of interest in quantum information, quantum computing and quantum metrology. Metrologically useful entangled states of large atomic ensembles have been experimentally realized [1, 2, 3, 4, 5, 6, 7, 8, 9, 10], but these states display Gaussian spin distribution functions with a non-negative Wigner function. Non-Gaussian entangled states have been produced in small ensembles of ions [11, 12], and very recently in large atomic ensembles [13, 14, 15]. Here, we generate entanglement in a large atomic ensemble via the interaction with a very weak laser pulse; remarkably, the detection of a single photon prepares several thousand atoms in an entangled state. We reconstruct a negative-valued Wigner function, an important hallmark of nonclassicality, and verify an entanglement depth (minimum number of mutually entangled atoms) of 2910 190 out of 3100 atoms. Attaining such a negative Wigner function and the mutual entanglement of virtually all atoms is unprecedented for an ensemble containing more than a few particles. While the achieved purity of the state is slightly below the threshold for entanglement-induced metrological gain, further technical improvement should allow the generation of states that surpass this threshold, and of more complex Schrödinger cat states for quantum metrology and information processing.