Continuous-variable entanglement on a chip

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Abstract

Encoding quantum information in continuous variables, as the quadrature of electromagnetic fields, is a powerful approach to quantum information science and technology1. Continuous-variable entanglement (light beams in Einstein–Podolsky–Rosen, or EPR2, states) is a key resource for quantum information protocols3 and enables hybridization between continuous-variable and single-photon discrete-variable qubit systems4. However, continuous-variable systems are currently limited by their implementation in free-space optical networks, and the demand for increased complexity, low loss, high-precision alignment and stability, as well as hybridization, require an alternative approach. Here we present an integrated photonic implementation of the key capabilities for continuous-variable quantum technologies—the generation and characterization of EPR beams in a photonic chip. When combined with integrated squeezing and non-Gaussian operations, these results will open the way to universal quantum information processing with light.

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Figure 1: Experimental set-up.
Figure 2: On-chip homodyne detection of squeezing.
Figure 3: EPR entanglement verification.

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Acknowledgements

The authors thank H. Bachor for advice. This work was partly supported by the Project for Developing Innovation Systems (PDIS), Grants-in-Aid for Scientific Research (GIA) and the Advanced Photon Science Alliance (APSA) commissioned by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan, the Nippon Telegraph and Telephone Corporation (NTT), the Engineering and Physical Sciences Research Council (EPSRC), the European Research Council (ERC), Photonic Integrated Compound Quantum Encoding (PICQUE), Breaking the Barriers of Optical Integration (BBOI), the US Army Research Office (ARO; grant no. W911NF-14-1-0133) and the US Air Force Office of Scientific Research (AFOSR). J.L.O. acknowledges a Royal Society Wolfson Merit Award and a Royal Academy of Engineering Chair in Emerging Technologies.

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Contributions

A.F. and J.L.O. planned the project. A.F. supervised the project. G.M. and K.M. conducted the experiment and data analysis. J.L.O. and A.P. developed the waveguide chip. T.H. provided experimental information. G.M., A.P., J.L.O. and A.F. wrote the manuscript with assistance from T.H. and K.M.

Corresponding author

Correspondence to Akira Furusawa.

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The authors declare no competing financial interests.

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Masada, G., Miyata, K., Politi, A. et al. Continuous-variable entanglement on a chip. Nature Photon 9, 316–319 (2015). https://doi.org/10.1038/nphoton.2015.42

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