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Entanglement with a mode observable via a tunable interaction with a qubit

Małgorzata Strzałka1,2, Radim Filip3, and Katarzyna Roszak1

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Phys. Rev. A 113, 062422 – Published 8 June, 2026

DOI: https://doi.org/10.1103/qdwp-8byl

Abstract

We study the possibility of detection of “spin-boson” entanglement by qubit-only measurements. Such entanglement is impossible to detect by previously proposed schemes that involve a fixed system-environment interaction because of inherent symmetries within the coupling and the initial state of the environment. We take advantage of the possibility of tuning the qubit-environment coupling, which is available in some qubit realizations. As an example, we study a superconducting transmon qubit interacting with a microwave cavity, which is one of such systems and is, furthermore, essential in the context of quantum information processing. We propose suitable Hamiltonian parameters for the preparation and measurement phases of the detection scheme that allow for an experimental test, and verify that the reported signal is still non-negligibly large at finite temperatures.

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Phys. Rev. A 113, 062422– Published 8 June, 2026
  • Received 17 December 2025
  • Accepted 21 May 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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