Observation of a topological defect state in the quantum Rabi model
Abstract
Synthetic lattices built from hybrid qubit-oscillator systems provide a platform for exploring topology, with multiple physical degrees of freedom enabling control over lattice geometry. A single spin-oscillator pair, described by the quantum Rabi model, provides a minimal system supporting a topological defect state on a lattice formed from the oscillator's infinite ladder of number states. However, the realization of the defect state and its robustness remain experimentally unexplored. Here we realize a topological defect state of the quantum Rabi model in a single trapped 171Yb+ ion. As a coupling phase varies, reconstructed phase-space distributions yield centroid trajectories with windings of one and zero in two regimes, linking discrete-lattice topology to the geometry of the oscillator's continuous position-momentum space. The measured spin response to drive-amplitude modulation relates the stability of spin polarization to energy gaps and allowed transitions. Together, these results establish a minimal quantum system for realizing and probing topological defect states.
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BibTeX
@misc{lee2026observation,
title = {{Observation of a topological defect state in the quantum Rabi model}},
author = {Kyungmin Lee and Jiyong Kang and Sunkyu Yu and Jaehun You and Wonhyeong Choi and Taehyun Kim},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2609.34389},
eprint = {2609.34389},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.34389},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Observation of a topological defect state in the quantum Rabi model
AU - Kyungmin Lee
AU - Jiyong Kang
AU - Sunkyu Yu
AU - Jaehun You
AU - Wonhyeong Choi
AU - Taehyun Kim
PY - 2026
DA - 2026/10/05
PB - arXiv
DO - 10.48550/arxiv.2609.34389
UR - https://arxiv.org/abs/2609.34389
AB - Synthetic lattices built from hybrid qubit-oscillator systems provide a platform for exploring topology, with multiple physical degrees of freedom enabling control over lattice geometry. A single spin-oscillator pair, described by the quantum Rabi model, provides a minimal system supporting a topological defect state on a lattice formed from the oscillator's infinite ladder of number states. However, the realization of the defect state and its robustness remain experimentally unexplored. Here we realize a topological defect state of the quantum Rabi model in a single trapped ^171Yb^+ ion. As a coupling phase varies, reconstructed phase-space distributions yield centroid trajectories with windings of one and zero in two regimes, linking discrete-lattice topology to the geometry of the oscillator's continuous position-momentum space. The measured spin response to drive-amplitude modulation relates the stability of spin polarization to energy gaps and allowed transitions. Together, these results establish a minimal quantum system for realizing and probing topological defect states.
ER -