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arXiv · 2609.34389

Experimental Realization and Phase-Space Winding of a Topological Defect State in the Quantum Rabi Model

Kyungmin Lee·Jiyong Kang·Sunkyu Yu·Jaehun You·Wonhyeong Choi·Taehyun Kim
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Abstract

We experimentally realize a topological defect state of the quantum Rabi model in a single trapped $^{171}\mathrm{Yb}^{+}$ ion. The state is supported by a tunable interface arising from the oscillator's intrinsic number-dependent coupling in the Fock-state-lattice representation. We independently prepare the state at each sideband-phase setting and reconstruct its motional phase-space distribution using characteristic-function tomography. The resulting Wigner-centroid trajectories exhibit winding numbers of one and zero in the two coupling regimes. Changing the carrier amplitude rescales the trajectories while preserving their windings. Carrier-amplitude modulation provides a complementary dynamical probe, yielding a spin response consistent with the excitation gaps and accessible transition channels from the defect state. The experiment connects topological defect-state physics in a nonuniform synthetic lattice to the measurable phase-space geometry of a hybrid spin-boson system.

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Kyungmin Lee, Jiyong Kang, Sunkyu Yu, Jaehun You, Wonhyeong Choi, Taehyun Kim. 2026-09-28. Experimental Realization and Phase-Space Winding of a Topological Defect State in the Quantum Rabi Model. https://arxiv.org/abs/2609.34389

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