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arXiv:2608.14206

Synthesizing In-Bulk Topological Corner States via Giant Atoms

Zhao-Min Gao, Xin Wang

quant-phSubmitted Aug 14, 2026• Announced Aug 17, 2026
arXivHTMLPDF

Abstract

Corner states in higher-order topological insulators are typically confined to geometric corners, limiting their flexibility for scalable quantum information processing. We propose a scheme to synthesize topological corner states at arbitrary positions within the bulk of a two-dimensional Su-Schrieffer-Heeger (SSH) lattice by coupling it to giant atoms. By engineering an L-shaped multi-point coupling that satisfies the vacancy-like dressed state (VDS) condition, where the photonic wavefunction vanishes at the coupling sites to form an artificial bulk boundary, we derive the conditions for synthesizing a zero-energy corner state at any target position. We demonstrate that the engineered corner state exhibits high fidelity and spatial localization, remaining robust against realistic disorder. Extending to multi-atom networks, we realize a versatile quantum switch via a giant superatom, enabling multi-channel control over 0D corner states and 1D edge states through the dual-resonance condition. Furthermore, we demonstrate the coherent interactions between two giant atoms mediated by VDS-engineered corner states. Governed by a sublattice selection rule, the coupling activates exclusively in intersecting configurations and decays exponentially with distance. Our work establishes a highly reconfigurable platform for embedding topological boundary modes within the bulk, offering a robust pathway for scalable topological quantum networks.

Comments
12 pages, 12 figures

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Corner states in higher-order topological insulators are typically confined to geometric corners, limiting their flexibility for scalable quantum information processing. We propose a scheme to synthesize topological corner states at arbitrary positions within the bulk of a two-dimensional Su-Schrieffer-Heeger (SSH) lattice by coupling it to giant atoms. By engineering an L-shaped multi-point coupling that satisfies the vacancy-like dressed state (VDS) condition, where the photonic wavefunction vanishes at the coupling sites to form an artificial bulk boundary, we derive the conditions for synthesizing a zero-energy corner state at any target position. We demonstrate that the engineered corner state exhibits high fidelity and spatial localization, remaining robust against realistic disorder. Extending to multi-atom networks, we realize a versatile quantum switch via a giant superatom, enabling multi-channel control over 0D corner states and 1D edge states through the dual-resonance condition. Furthermore, we demonstrate the coherent interactions between two giant atoms mediated by VDS-engineered corner states. Governed by a sublattice selection rule, the coupling activates exclusively in intersecting configurations and decays exponentially with distance. Our work establishes a highly reconfigurable platform for embedding topological boundary modes within the bulk, offering a robust pathway for scalable topological quantum networks.
Photonic state engineering in waveguide QED is typically based on local light-matter interactions. This limits its control over the spatial structure of bound photonic states. Here, we demonstrate a distinct mechanism arising from the interplay between nonlocal giant-atom coupling and topological band structure. Specifically, we consider giant atoms coupled to a Su-Schrieffer-Heeger waveguide and show that this configuration enables a controllable energy-level crossing protected by the topological gap. Adiabatically sweeping the atomic detuning across the crossing leads to a controlled exchange between distinct photonic bound states. In a two-giant-atom configuration, this mechanism achieves high-fidelity conversion of a spatially splitting state into a combining state. Extending this scheme to three-giant atoms, we further realize robust, shape-preserving photon transfer mediated by sequential in-gap crossings. Our results demonstrate how topology and nonlocal light-matter coupling can be combined to achieve programmable control of bound photonic states in waveguide QED platforms.
The active manipulation of topologically protected states represents a pivotal frontier for quantum technologies, offering a unique confluence of topological robustness and precise quantum control. We propose an adiabatic pumping scheme for the long-range transfer of topological corner states in a two-dimensional Su-Schrieffer-Heeger model. The protocol utilizes a modular lattice architecture composed of four topologically distinct subblocks, enabling the modulation of a topological dark state by precise tuning of lattice couplings. This approach is based on coherent tunneling by adiabatic passage among topological corner and interface states. We establish a multi-level model for the adiabatic pumping that provides an accurate description of the underlying mechanism. In comparison with a sequential two-stage Thouless pumping, our protocol offers superior performance in both transfer fidelity and efficiency.
Simulating higher-order topological materials in synthetic quantum matter is an active research frontier for its theoretical significance in fundamental physics and promising applications in quantum technologies. Here we experimentally implement two-dimensional (2D) momentum lattices with highly programmable ability using ultracold 87Rb atoms. Through precise control of experimental parameters, we simulate a 2D Su-Schrieffer-Heeger model with this technique, and observe the characteristic dynamics of corner and edge-bound states, where the corner state is identified as a higher-order topological bound state in the continuum. We further study the adiabatic preparation of the corner state by engineering evolutions with time-dependent Hamiltonians. We also demonstrate the higher-order topological phase transition by measuring both the bulk topological invariant and the topological corner state. Our new platform opens the avenue for exploring the exotic dynamics and topology in higher synthetic dimensions, making use of the rich degrees of freedom of cold atoms systems.
We study an adiabatic topological passage of two Su-Schrieffer-Heeger (SSH) chains mediated by a giant atom. When two finite SSH chains are in the topological phase and the frequency of the giant atom is equal to the center frequency of the SSH chains, the system is reduced to a subsystem that describes the coupling of a giant atom to the edge states of two SSH chains. In this case, we can find dark states that act as adiabatic topological passages. This allows us to adiabatically transfer excitations of the giant atom to either one end of two SSH chains in a fully controllable way. In addition, we show good robustness of the adiabatic topological passages to both giant atom frequency mismatch and the coupling disorders in two SSH chains. Our study provides a method to realize quantum information processing and fabricate quantum optical devices based on the coupling of the giant atom to topological matter.
Simulating higher-order topological materials in synthetic quantum matter is an active research frontier for its theoretical significance in fundamental physics and promising applications in quantum technologies. Here we experimentally implement two-dimensional (2D) momentum lattices with highly programmable ability using ultracold 87Rb atoms. Through precise control of experimental parameters, we simulate a 2D Su-Schrieffer-Heeger model with this technique, and observe the characteristic dynamics of corner and edge-bound states, where the corner state is identified as a higher-order topological bound state in the continuum. We further study the adiabatic preparation of the corner state by engineering evolutions with time-dependent Hamiltonians. We also demonstrate the higher-order topological phase transition by measuring both the bulk topological invariant and the topological corner state. Our new platform opens the avenue for exploring the exotic dynamics and topology in higher synthetic dimensions, making use of the rich degrees of freedom of cold atoms systems.
The giant-atom topological-waveguide-QED systems have recently emerged as a promising platform for manipulating light-matter interactions. The combination of the multiple-point couplings and topological phase effect could lead to rich physical phenomena and effects. Here, we study single-photon scattering in a Su-Schrieffer-Heeger (SSH) waveguide coupled to either one or two two-level giant atoms. We assume that each giant atom is coupled to the waveguide via two coupling points and hence there exist four and sixteen coupling configurations for the single-giant-atom case and two-giant-atom separate coupling case, respectively. By solving the single-photon scattering problem in the real space, we obtain the exact expressions of the single-photon scattering amplitudes. It is found that a single photon in the SSH waveguide can be completely reflected or transmitted by choosing proper coupling configurations, coupling-point distances, atomic resonance frequency, and dimerization parameter. In addition, under proper parameter conditions, the scattering spectra are periodically modulated by the coupling-point distances. We also find that the collective behavior of the two giant atoms can be adjusted by quantum interference effect and topological effect and that the single-photon scattering spectra can exhibit the Lorentzian, super-Gaussian, electromagnetically induced transparencylike, and asymmetric Fano line shapes for some coupling configurations. This work will inspire the development of controllable single-photon devices based on the giant-atom topological-waveguide-QED systems.