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QI: Fachverband Quanteninformation

QI 14: Quantum Information Poster Session

QI 14.2: Poster

Mittwoch, 11. März 2026, 18:00–21:00, P4

Entanglement with a mode observable via a tunable interaction with a qubit — •Malgorzata Strzalka^1,2, Radim Filip³, and Katarzyna Roszak¹ — ¹FZU - Institute of Physics of the Czech Academy of Sciences,. — ²Faculty of Mathematics and Physics, Charles University. — ³Department of Optics, Palacký University.

We propose a qubit-environment entanglement (QEE) detection scheme for time dependent pure dephasing Hamiltonians. We study the entanglement for a transmon qubit interacting with an environment of microwave cavity photons. The QEE detection schemes that were previously developed for interactions that lead to pure decoherence of the qubit are based on measurements and operations performed only on the qubit alone [1]. Yet they could not be used in the studied scenario because of inherent symmetries in the Hamiltonian. We show that it is possible to override this problem by using different Hamiltonias in the preparation and the measurement stage. We take advantage of the possibility of tuning of the qubit-environment coupling to detect entanglement. Qubit-oscillator entanglement is seen to play a essential role in developing bosonic quantum technology. We previously studied the evolution of QEE for the same system [2] and now we present how the developed detection scheme can signify this type of entanglement. The scheme can be also used for other systems, where the decoherence is predominantly pure dephasing.

[1] M. Strzalka and K. Roszak, Phys. Rev. A 104, 042411 (2021).

[2] M. Strzalka et al. Phys. Rev. A 109, 032412 (2024).

Keywords: qubit-environment entanglement; detection scheme; transmon qubits