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Observation of eight-photon entanglement


The creation of increasingly large multipartite entangled states is not only a fundamental scientific endeavour in itself1,2,3, but is also the enabling technology for quantum information4,5. Tremendous experimental effort has been devoted to generating multiparticle entanglement with a growing number of qubits6,7,8,9,10,11,12,13,14,15,16. So far, up to six spatially separated single photons10,11,12,13,14 have been entangled based on parametric downconversion17. Multiple degrees of freedom of a single photon have been exploited to generate forms of hyper-entangled states18,19. Here, using new ultra-bright sources of entangled photon pairs20, an eight-photon interferometer and post-selection detection, we demonstrate for the first time the creation of an eight-photon Schrödinger cat state1 with genuine multipartite entanglement. The ability to control eight individual photons represents a step towards optical quantum computation, and will enable new experiments on, for example, quantum simulation21,22, topological error correction23 and testing entanglement dynamics under decoherence24.

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Figure 1: Experimental scheme for generating eight-photon Schrödinger cat states.
Figure 2: Experimental set-up.
Figure 3: Experimental results for the eight-photon Schrödinger cat state.


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The authors thank M. Cramer for useful discussions. This work was supported by the National Natural Science Foundation of China, the Chinese Academy of Sciences and the National Fundamental Research Program (grant no. 2011CB921300).

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Authors and Affiliations



X.-C.Y., X.-H.B., Y.-A.C. and J.-W.P. conceived and designed the research. X.-C.Y., T.-X.W., P.X., H.L., G.-S.P. and C.-Z.P. carried out the experiment. X.-H.B. programmed the FPGA logic. C.-Y.L. contributed theoretical analysis tools. X.-C.Y. and Y.-A.C. analysed the data. X.-C.Y., C.-Y.L., Y.-A.C. and J.-W.P. wrote the manuscript. C.-Y.L., Y.-A.C. and J.-W.P. supervised the project.

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Correspondence to Chao-Yang Lu or Jian-Wei Pan.

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The authors declare no competing financial interests.

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Yao, XC., Wang, TX., Xu, P. et al. Observation of eight-photon entanglement. Nature Photon 6, 225–228 (2012).

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