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  • Open Access

Interferometric detection of continuous-variable entanglement using two states

Elena Callus1,*, Martin Gärttner1,†, and Tobias Haas2,‡

  • *Contact author: elena.callus@uni-jena.de
  • †Contact author: martin.gaerttner@uni-jena.de
  • ‡Contact author: tobias.haas@ulb.be
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Phys. Rev. A 112, 033704 – Published 5 September, 2025

DOI: https://doi.org/10.1103/4wzg-fc7b

Abstract

The efficient witnessing and certification of entanglement is necessitated by its ubiquitous use in various aspects of quantum technologies. In the case of continuous-variable bipartite systems, the Shchukin-Vogel hierarchy gives necessary conditions for separability in terms of moments of the mode operators. In this work we derive mode-operator-based witnesses for continuous-variable bipartite entanglement relying on the interference of two states. Specifically, we show how one can access higher moments of the mode operators, crucial for detecting entanglement of non-Gaussian states, using a single beamsplitter with variable phase and photon-number-resolving detectors. We demonstrate that the use of an entangled state paired with a suitable reference state is sufficient to detect entanglement in, e.g., two-mode squeezed vacuum, NOON states, and mixed entangled cat states. We also take into account experimental noise, including photon loss and detection inefficiency, as well as finite measurement statistics.

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Phys. Rev. A 112, 033704– Published 5 September, 2025
  • Received 12 May 2025
  • Accepted 21 August 2025
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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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