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Experimental randomness amplification

Nature volume 653, pages 1033–1038 (2026) Cite this article

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Abstract

Realistic quantum information processing devices are inherently imperfect, leading to computational errors that require quantum error correction. Likewise, random bits generated by such devices are flawed and must be enhanced to be usable for applications such as generating cryptographic keys. This enhancement of randomness quality is achieved through a protocol known as randomness amplification1. Here we report on an experiment that implements such a protocol. Randomness amplification is device-independent, making no assumptions about the internal workings of the quantum devices. It requires executing a loophole-free Bell test2,3,4 within a specific parameter regime that involves both a high Bell violation and a high repetition rate. The experimental demonstration is made possible by a combination of theoretical advances, which allow for protocols with an experimentally realistic parameter regime, and experimental progress that achieves this regime with superconducting circuits. Crucially, randomness amplification has been proven to be impossible by purely classical means5. This experiment therefore demonstrates a definitive quantum advantage—leveraging quantum technology to accomplish a task unattainable by classical information processing.

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Fig. 1: Schematic diagram of the randomness amplification protocol.
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Fig. 2: Comparative performance of a selection of Bell-test-based experiments for device-independent randomness amplification.
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Fig. 3: Comparison of traditional quantum random number generation with device-independent randomness amplification.
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Fig. 4: Full experimental protocol.
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Fig. 5: Bell violation versus number of trials.
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Data availability

The data that support the findings of this study have been deposited in the ETH Zurich Research Collection and are publicly available at https://doi.org/10.3929/ethz-c-000797430.

Code availability

The code used for randomness extraction and data analysis has been deposited in the ETH Zurich Research Collection and is publicly available at https://doi.org/10.3929/ethz-c-000797430.

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Acknowledgements

We thank R. Conchello Vendrell for contributions to the software framework; R. Schlatter for support with the operation of the cryogenic set-up; A. Efimova for assistance with the synchronization of the electronic instruments; and N. Gisin and M. Fadel for comments on the paper. The work was funded by the European Union’s Horizon 2020 FET-Open project SuperQuLAN (899354) and by ETH Zurich. M.S., R.W. and R.R. were supported by the Air Force Office of Scientific Research (AFOSR), grant number FA9550-19-1-0202, the QuantERA project eDICT, the SNSF project number 20QU-1_225171, and the National Centre of Competence in Research SwissMAP. R.W. acknowledges support from the Ministry of Culture and Science of North Rhine-Westphalia via the NRW-Rückkehrprogramm.

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Authors and Affiliations

  1. Department of Physics, ETH Zurich, Zurich, Switzerland

    Anatoly Kulikov, Simon Storz, Josua D. Schär, Martin Sandfuchs, Ramona Wolf, Florence Berterottière, Christoph Hellings, Andreas Wallraff & Renato Renner

  2. Quantum Center, ETH Zurich, Zurich, Switzerland

    Anatoly Kulikov, Simon Storz, Josua D. Schär, Martin Sandfuchs, Ramona Wolf, Florence Berterottière, Christoph Hellings, Andreas Wallraff & Renato Renner

  3. Naturwissenschaftlich-Technische Fakultät, Universität Siegen, Siegen, Germany

    Ramona Wolf

  4. Universität Innsbruck, Institut für Theoretische Physik, Innsbruck, Austria

    Ramona Wolf

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Contributions

A.K., S.S. and J.D.S. assembled the experimental set-up, performed the measurements and analysed the data. A.K., S.S., F.B., C.H. and J.D.S. developed the control software. M.S. and R.W. performed the theoretical analysis, randomness extraction and developed the security proofs. A.K., S.S., R.W., M.S., J.D.S. and R.R. wrote the paper with input from all authors. R.R. and A.W. supervised the project.

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Correspondence to Anatoly Kulikov.

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Kulikov, A., Storz, S., Schär, J.D. et al. Experimental randomness amplification. Nature 653, 1033–1038 (2026). https://doi.org/10.1038/s41586-026-10521-8

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