arXiv subjects

Ze-Guo Chen

Publications and source records attributed to Ze-Guo Chen.

15 recordsLinked to original sources

arXiv2025

Direct Measurement of Zak Phase and Higher Winding Numbers in an Electroacoustic Cavity System

Topological phases are states of matter defined by global topological invariants that remain invariant under adiabatic parameter variations, provided no topological phase transition occurs. This endows them with intrinsic robustness against local perturbations. Experimentally, these phases are often identified indirectly by observing robust boundary states, protected by the bulk-boundary correspondence. Here, we propose an experimental method for the direct measurement of topological invariants via adiabatic state evolution in electroacoustic coupled resonators, where time-dependent cavity modes effectively emulate the bulk wavefunction of a periodic system. Under varying external driving fields, specially prepared initial states evolve along distinct parameter-space paths. By tracking the relative phase differences among states along these trajectories, we successfully observe the quantized Zak phase in both the conventional Su-Schrieffer-Heeger (SSH) model and its extension incorporating with next-nearest-neighbor coupling. This approach provides compelling experimental evidence for the precise identification of topological invariants and can be extended to more complex topological systems.

quant-ph↗

arXiv2025

Realizing Bloch Dynamics in a Low-Cost Electrically Driven Acoustic Two-Level System

Unlike classical bits that can only occupy one of two discrete states, quantum bits (qubits) can exist in arbitrary coherent superpositions of the ground and excited states. This fundamental distinction grants qubits enhanced capabilities for information storage and processing. The Bloch sphere provides an intuitive and powerful geometric framework for visualizing, characterizing, and controlling the dynamical evolution of a qubit under external driving fields. By mapping the state evolution onto the Bloch sphere, processes such as spin flips and phase accumulation can be vividly represented as trajectories, enabling direct insight into coherent control mechanisms. Here, we implement Bloch dynamics in a classical platform by constructing a tunable acoustic two-level system based on high-quality-factor electro-acoustic coupled cavities. Using programmable spatiotemporal external field modulation, we demonstrate full Bloch sphere control through classical analogs of quantum phenomena, including Rabi oscillations, Floquet dynamics, Ramsey interference, and spin echo sequences. Our results bridge coherent Bloch dynamics with classical wave control, revealing a versatile experimental platform for exploring quantum-inspired physics. Furthermore, the system exhibits exceptional capabilities for precision transient acoustic field shaping, enabled by high-fidelity pulse-driven modulation.

quant-ph↗

arXiv2025

Zeno Freezing and Anti-Zeno Acceleration of the Dynamic Evolution of Acoustic Topological Boundary States

Quantum measurements severely disrupt the dynamic evolution of a quantum system by collapsing the probabilistic wavefunction. This principle can be leveraged to control quantum states by effectively freezing the system's dynamics or enhancing transitions between states. These are known as the quantum Zeno effect (ZE) and anti-Zeno effect (AZE), respectively. However, it remains elusive how quantum measurements affect topological states, which are famous for their robustness against disorder and perturbations. Here, we theoretically and experimentally show that the dynamic evolution of topological boundary states (TBSs) can be controlled by quantum-like measurement (QLM). Our work is based on spatially modulated topological acoustic waveguide systems with varying parameters that adiabatically pump the TBS across the bulk to the opposite boundary. Therein, the QLM is emulated using a perturbation to the Hamiltonian known as the Zeno subspace. With the help of quantum metrics, we identify the general conditions for ZE and AZE, and experimentally demonstrate their effects in freezing and accelerating the tunneling of the TBS. Furthermore, we discover a tunneling mechanism by varying the strength of the QLM. These results highlight QLM as a versatile tool for manipulating topological states and wave propagation.

quant-ph↗

arXiv2023

Transient logic operations in acoustics through dynamic modulation

In quantum logic operations, information is carried by the wavefunction rather than the energy distribution. Therefore, the relative phase is essential. Abelian and non-Abelian phases can be emulated in classical waves using passive coupled waveguides with geometric modulation. However, the dynamic phases interference induced by waveguide structure variation is inevitable.To overcome the challenges, we introduce an electroacoustic coupled system that enables the precise control of phase distribution through dynamic modulation of hopping. Such effective hopping is electronically controlled and is utilized to construct various paths in parameter space. These paths lead to state evolution with matrix-valued geometric phases, which correspond to logic operations. We report experimental realizations of several logic operations, including $Y$ gate, $Z$ gate, Hadamard gate and non-Abelian braiding. Our work introduces a temporal process to manipulate transient modes in a compact structure, providing a versatile experimental testbed for exploring other logic gates and exotic topological phenomena.

quant-ph↗

arXiv2022

Non-Abelian braiding on photonic chips

Non-Abelian braiding has attracted significant attention because of its pivotal role in describing the exchange behaviors of anyons--a candidate for realizing quantum logics. The input and outcome of non-Abelian braiding are connected by a unitary matrix which can also physically emerge as a geometric-phase matrix in classical systems. Hence it is predicted that non-Abelian braiding should have analogues in photonics, but a feasible platform and the experimental realization remain out of reach. Here, we propose and experimentally realize an on-chip photonic system that achieves the non-Abelian braiding of up to five photonic modes. The braiding is realized by controlling the multi-mode geometric-phase matrix in judiciously designed photonic waveguide arrays. The quintessential effect of braiding--sequence-dependent swapping of photon dwell sites is observed in both classical-light and single-photon experiments. Our photonic chips are a versatile and expandable platform for studying non-Abelian physics, and we expect the results to motivate next-gen non-Abelian photonic devices.

physics.optics↗

arXiv2021

Observation of degenerate zero-energy topological states at disclinations in an acoustic lattice

Building upon the bulk-boundary correspondence in topological phases of matter, disclinations have recently been harnessed to trap fractionally quantized density of states (DoS) in classical wave systems. While these fractional DoS have associated states localized to the disclination's core, such states are not protected from deconfinement due to the breaking of chiral symmetry, generally leading to resonances which, even in principle, have finite lifetimes and suboptimal confinement. Here, we devise and experimentally validate in acoustic lattices a paradigm by which topological states bind to disclinations without a fractional DoS but which preserve chiral symmetry. The preservation of chiral symmetry pins the states at the mid-gap, resulting in their protected maximal confinement. The integer DoS at the defect results in two-fold degenerate states that, due to symmetry constraints, do not gap out. Our study provides a fresh perspective on the interplay between symmetry-protection in topological phases and topological defects, with possible applications in classical and quantum systems alike.

cond-mat.mes-hall↗

arXiv2021

Experimental Realization of Weyl Exceptional Rings in a Synthetic Three-Dimensional Non-Hermitian Phononic Crystal

Weyl points (WPs) are isolated degeneracies carrying quantized topological charges, and are therefore robust against Hermitian perturbations. WPs are predicted to spread to the Weyl exceptional rings (WERs) in the presence of non-Hermiticity. Here, we use a one-dimensional (1D) Aubry-Andre-Harper (AAH) model to construct a Weyl semimetal in a 3D parameter space comprised of one reciprocal dimension and two synthetic dimensions. The inclusion of non-Hermiticity in the form of gain and loss produces a WER. The topology of the WER is characterized by both its topological charge and non-Hermitian winding numbers. The WER is experimentally observed in a 1D phononic crystal with the non-Hermiticity introduced by active acoustic components. In addition, Fermi arcs are observed to survive the presence of non-Hermitian effect. We envision our findings to pave the way for studying the high-dimensional non-Hermitian topological physics in acoustics.

cond-mat.mes-hall↗

arXiv2021

Relaying Topological Interface States for Negative Refraction of Bulk Waves

Topological notions in physics have become a powerful perspective that leads to the discoveries of topological interface states (TISs). In this work, we present a scheme to achieve negative refraction by leveraging the properties of TISs in a valley photonic crystal (VPC). Due to the chiral characteristics, one type of the TISs deterministically possesses negative dispersion relation, which can cause an obliquely incident wave to undergo a negative lateral shift. By stacking multiple VPC interfaces, the TIS-induced lateral shifts can relay in the transmitted wave towards the far side of incidence. The resultant outgoing wave appears to have undergone negative refraction. This finding is verified in microwave experiments. Our scheme opens new application scenarios for topological systems in bulk wave manipulations.

physics.optics↗

arXiv2020

Four-Dimensional Higher-Order Chern Insulator and Its Acoustic Realization

We present a theoretical study and experimental realization of a system that is simultaneously a four-dimensional (4D) Chern insulator and a higher-order topological insulator (HOTI). The system sustains the coexistence of (4-1)-dimensional chiral topological hypersurface modes (THMs) and (4-2)-dimensional chiral topological surface modes (TSMs). Our study reveals that the THMs are protected by second Chern numbers, and the TSMs are protected by a topological invariant composed of two first Chern numbers, each belonging a Chern insulator existing in sub-dimensions. With the synthetic coordinates fixed, the THMs and TSMs respectively manifest as topological edge modes (TEMs) and topological corner modes (TCMs) in the real space, which are experimentally observed in a 2D acoustic lattice. These TCMs are not related to quantized polarizations, making them fundamentally distinctive from existing examples. We further show that our 4D topological system offers an effective way for the manipulation of the frequency, location, and the number of the TCMs, which is highly desirable for applications.

physics.app-ph↗

arXiv2020

Landau-Zener Transition in Topological Acoustic Pumping

Quantized charge pumping is a robust adiabatic phenomenon uniquely existing in topologically nontrivial systems. Such topological pumping not only brings fundamental insights to the evolution of states under the protection of topology but also provides a vital approach for the study of higher-dimensional topological phases. In this work, we demonstrate topological pumping in an acoustic waveguide system by showing the successful pumping of topological boundary states (TBSs) across the bulk to the opposite edge. By exploring the finite-size induced mini-gap between two TBS bands, we unveil the quantitative condition for the breakdown of adiabaticity in the system by demonstrating the Landau-Zener transition with both theory and experiments. Our results not only open a new route for future investigations of topological acoustics but also establish non-adiabatic transitions as a new degree of freedom for manipulating topological states.

physics.app-ph↗

arXiv2019

Three-dimensional acoustic double-zero-index medium with a Dirac-like point

We report a design and experimental realization of a three-dimensional (3D) acoustic double-zero-index medium (DZIM), whose effective mass density and compressibility are nearly zero simultaneously. The DZIM is constructed from a cubic lattice of three orthogonally-aligned metal rods in air. The combination of lattice symmetry and accidental degeneracy yields a four-fold degenerate point with conical dispersion at the Brillouin zone center, where the material becomes a 3D DZIM. Though occupying a finite volume, the 3D DZIM maintains the wave properties of a "void space," and enables rich applications. For demonstration, we fabricate an acoustic "periscope" by placing the designed 3D DZIM inside a 3D bending waveguide, and observe the unusual wave tunneling effect through this waveguide with undisturbed planar wavefront. Our findings establish a practical route to realize 3D DZIM as an effective acoustic "void space," which offers unprecedented opportunities for advanced sound manipulation.

physics.app-ph↗

arXiv2017

Acoustic frequency filter based on anisotropic topological phononic crystals

There are growing efforts in constructing topological edge states in classical wave system. However, most of the work study the existence, creation and properties of the edge states, and the demonstration of application is highly desirable. Here, we present our design of a two-dimensional anisotropic phononic crystal that exhibits tunable topological phases. We further explore the contribution of anisotropy and show that the bandgap topology is also related to particular directions and frequency. Such frequency dependent behavior can be utilized as a frequency filter.

physics.app-ph↗

arXiv2016

Pseudo-time-reversal symmetry and topological edge states in two-dimensional acoustic crystals

We propose a simple two-dimensional acoustic crystal to realize topologically protected edge states for acoustic waves. The acoustic crystal is composed of a triangular array of core-shell cylinders embedded in a water host. By utilizing the point group symmetry of two doubly degenerate eigenstates at the Γpoint, we can construct pseudo-time-reversal symmetry as well as pseudo-spin states in this classical system. We develop an effective Hamiltonian model for the associated dispersion bands around the Brillouin zone center, and find the inherent link between the band inversion and the topological phase transition. With numerical simulations, we unambiguously demonstrate the unidirectional propagation of acoustic edge states along the interface between a topologically nontrivial acoustic crystal and a trivial one, and the robustness of the edge states against defects with sharp bends. Our work provides a new design paradigm for manipulating and transporting acoustic waves in a topologically protected manner. Technological applications and devices based on our design are expected in various frequency ranges of interest, spanning from infrasound to ultrasound.

cond-mat.mtrl-sci↗

arXiv2015

Tunable topological phononic crystals

Topological insulators, first observed in electronic systems, have inspired many analogues in photonic and phononic crystals in which remarkable one-way propagation edge states are supported by topologically nontrivial bandgaps. Such bandgaps can be achieved by breaking the time-reversal symmetry to lift the degeneracy associated with Dirac cones at the corners of the Brillouin zone. Here, we report on our construction of a phononic crystal exhibiting a Dirac-like cone in the Brillouin zone center. We demonstrate that simultaneously breaking the time-reversal symmetry and altering the geometric size of the unit cell result in a topological transition that is verified by the Chern number calculation and edge mode analysis. The topology of the bandgap is tunable by varying both the velocity field and the geometric size; such tunability may dramatically enrich the design and use of acoustic topological insulators.

cond-mat.mes-hall↗

arXiv2014

Accidental degeneracy of double Dirac cones in a phononic crystal

Artificial honeycomb lattices with Dirac cone dispersion provide a macroscopic platform to study the massless Dirac quasiparticles and their novel geometric phases. In this paper, a quadruple-degenerate state is achieved at the center of Brillouin zone (BZ) in a two-dimensional honeycomb lattice phononic crystal, which is a result of accidental degeneracy of two double-degenerate states. In the vicinity of the quadruple-degenerate state, the dispersion relation is linear. Such quadruple degeneracy is analyzed by rigorous representation theory of groups. Using method, a reduced Hamiltonian is obtained to describe the linear Dirac dispersion relations of such quadruple-degenerate state, which is well consistent with the simulation results. Near such accidental degeneracy, we observe some unique wave propagating properties, such as defect insensitive propagating character and Talbot effect.

cond-mat.mes-hall↗