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  • Open Access

Witnessing quantum non-Gaussianity from intensity moments

Éva Rácz*, László Ruppert, and Radim Filip

  • Department of Optics, Palacky University, 17. listopadu 12, 771 46 Olomouc, Czech Republic

  • *Contact author: racz@optics.upol.cz
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Phys. Rev. Research 8, 033192 – Published 17 August, 2026

DOI: https://doi.org/10.1103/g4xr-6sw9

Abstract

Direct measurement of quantum non-Gaussianity requires some variant of a discrete photon-resolving detection, which is feasible only for low mean photon numbers. For a large mean photon number, intensity detection by linear photodiodes provides a continuous signal; therefore, the Fock probabilities of the unknown input state are not directly available. On the other hand, intensity moments can be measured directly, and photon-number moments can be estimated. Therefore, we derive and analyze a quantum non-Gaussianity witness based solely on the photon-number mean and variance (or alternatively, the second-order correlation g(2)) of an unknown state. Due to the simplicity of the used photon-number moments, the measurement results are easy to correct for losses and additive noise. We provide examples of simple amplification-based measurement schemes where our witness can be applied directly, thereby opening pathways to proof-of-principle tests and applications.

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Phys. Rev. Research 8, 033192– Published 17 August, 2026
  • Received 19 December 2025
  • Accepted 2 June 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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