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Ultra-large-scale continuous-variable cluster states multiplexed in the time domain


Quantum computers promise ultrafast performance for certain tasks1. Experimentally appealing, measurement-based quantum computation2 requires an entangled resource called a cluster state3, with long computations requiring large cluster states. Previously, the largest cluster state consisted of eight photonic qubits4 or light modes5, and the largest multipartite entangled state of any sort involved 14 trapped ions6. These implementations involve quantum entities separated in space and, in general, each experimental apparatus is used only once. Here, we circumvent this inherent inefficiency by multiplexing light modes in the time domain. We deterministically generate and fully characterize a continuous-variable cluster state7,8 containing more than 10,000 entangled modes. This is, by three orders of magnitude, the largest entangled state created to date. The entangled modes are individually addressable wave packets of light in two beams. Furthermore, we present an efficient scheme for measurement-based quantum computation on this cluster state based on sequential applications of quantum teleportation.

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Figure 1: Schematic of the experimental set-up and ultra-large-scale XEPR state.
Figure 2: XEPR states for sequential quantum teleportation.
Figure 3: Measured quantum correlations of the first fifty wave packets.
Figure 4: Quantum correlations of the XEPR state for the first 30,000 wave packets.

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This work was partly supported by the Project for Developing Innovation Systems (PDIS), Grants-in-Aid for Scientific Research (GIA), the Global Center of Excellence (G-COE) and the Advanced Photon Science Alliance (APSA) commissioned by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan, the Funding Program for World-Leading Innovative R&D on Science and Technology (FIRST) initiated by the Council for Science and Technology Policy (CSTP) of Japan, and the Australian Research Council (ARC) Centre of Excellence for Quantum Computation & Communication Technology (CQC2T; project number CE110001027). S.Y. acknowledges financial support from Advanced Leading Graduate Course for Photon Science (ALPS). R.U. acknowledges support from the Japan Society for the Promotion of Science (JSPS). S.A. acknowledges financial support from the Prime Minister's Australia Asia Award. N.C.M. was supported by the ARC (grant no. DE120102204).

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Authors and Affiliations



S.Y., R.U. and S.A. planned and designed the experiment under the supervision of J.Y., H.Y. and A.F., based on the proposal by N.C.M. The experimental set-up were designed by S.Y., and the optical set-up was constructed by C.S., T.K. and S.Y. The fibre alignment system was built by S.S. The theory was formulated by R.U., S.A., N.C.M. and J.Y. R.U. designed and constructed the data acquisition system. S.A. designed and constructed the digital control system. R.U., S.A., T.K. and S.Y. conducted the data analysis. H.Y. assisted in noise analysis. S.Y. and S.A. wrote the manuscript with assistance from the team.

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Correspondence to Akira Furusawa.

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The authors declare no competing financial interests.

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Yokoyama, S., Ukai, R., Armstrong, S. et al. Ultra-large-scale continuous-variable cluster states multiplexed in the time domain. Nature Photon 7, 982–986 (2013).

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