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A quantum-bit encoding converter

Nature Photonics volume 17, pages 165–170 (2023)Cite this article

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Abstract

From telecommunications to computing architectures, the realm of classical information hinges on converter technology to enable the exchange of data between digital and analogue formats, a process now routinely performed across a variety of electronic devices. A similar exigency also exists in quantum information technology, where different frameworks are being developed for quantum computing, communication and sensing. Thus, efficient quantum interconnects are a major need to bring these parallel approaches together and scale up quantum information systems. So far, however, the conversion between different optical quantum-bit encodings has remained challenging due to the difficulty of preserving fragile quantum superpositions and the demanding requirements for postselection-free implementations. Here we demonstrate such a conversion of quantum information between the two main paradigms, namely discrete- and continuous-variable qubits. We certify the protocol on a complete set of single-photon qubits, successfully converting them to cat-state qubits with fidelities exceeding the classical limit. Our result demonstrates an essential tool for enabling interconnected quantum devices and architectures with enhanced versatility and scalability.

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Fig. 1: An optical encoding converter for quantum interconnects.
Fig. 2: Experimental set-up.
Fig. 3: Qubit characterization before and after conversion.
Fig. 4: Characterization of the conversion process.

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Data availability

The data supporting the findings of this study are available from the corresponding author on reasonable request.

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Acknowledgements

This work was supported by the QuantERA grant ShoQC, by the French National Research Agency (HyLight project ANR-17-CE30-0006, ShoQC project 19-QUAN-0005-05) and by the Horizon 2020 Research and Innovation Programme via the Twinning project NonGauss (951737). G.G. was supported by the European Union (Marie Curie Fellowship HELIOS IF-749213) and T.D. by Region Ile-de-France in the framework of DIM SIRTEQ. J.L. is a member of the Institut Universitaire de France.

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Author notes

  1. Hanna Le Jeannic

    Present address: Laboratoire Kastler Brossel, Sorbonne Université, CNRS, ENS-Université PSL, Collège de France, Paris, France

  2. Giovanni Guccione

    Present address: Centre for Quantum Computation and Communication Technology, Department of Quantum Science and Technology, Research School of Physics, The Australian National University, Canberra, Australian Capital Territory, Australia

  3. Adrien Cavaillès

    Present address: LightOn, Paris, France

Authors and Affiliations

  1. Laboratoire Kastler Brossel, Sorbonne Université, CNRS, ENS-Université PSL, Collège de France, Paris, France

    Tom Darras, Beate Elisabeth Asenbeck, Giovanni Guccione, Adrien Cavaillès & Julien Laurat

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  1. Tom Darras
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  2. Beate Elisabeth Asenbeck
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  3. Giovanni Guccione
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Contributions

T.D. and B.E.A. performed the experiment, developed the implementation techniques and analysed the data. G.G., A.C. and H.L.J. contributed to the preparation of the setup. J.L. designed the research and supervised the project. All authors discussed the results and contributed to the writing of the manuscript.

Corresponding author

Correspondence to Julien Laurat.

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Competing interests

T.D. and J.L. are co-founders and shareholders of Welinq. A patent (FR2114170) is pending for the present invention, with T.D., B.E.A., G.G., A.C. and J.L. as inventors. H.L.J. declares no competing interests.

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Nature Photonics thanks Hyunseok Jeong and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Information

Supplementary Discussion, Figs. 1–4 and Tables 1–4.

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Darras, T., Asenbeck, B.E., Guccione, G. et al. A quantum-bit encoding converter. Nat. Photon. 17, 165–170 (2023). https://doi.org/10.1038/s41566-022-01117-5

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