arXiv subjects

Hongzheng Wu

Publications and source records attributed to Hongzheng Wu.

8 recordsLinked to original sources

arXiv2026

Tunable Statistics-Induced Caging in the Anyon-Hubbard Model

We study the quantum dynamics of two interacting anyons in the Anyon-Hubbard model on a four-site plaquette, a system that is exactly mappable to a Bose-Hubbard model. We reveal that static Aharonov-Bohm (AB) caging, induced by only specific statistical phases, emerges in the strongly interacting limit but breaks down under weak interparticle interactions. To address this, we demonstrate that statistical-factor-induced AB caging can be dynamically restored via Floquet engineering. This dynamical mechanism, governed by the synthetic Floquet flux and the anyonic statistical phase, extends the caging effect into the weakly interacting regime across the full spectrum of statistical phases. Furthermore, we show that the external drive enables the selective caging of anyons, providing an efficient approach for manipulating anyons and identifying statistical phases.

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arXiv2026

Chiral Quantum Transport with Perfect Circulation: From Floquet Engineering toAnyonic Dynamics

Perfect chiral circulation-the sequential transfer of a quantum state around a closed loop with unit fidelity-has been achieved in specific few-site systems, yet the universal physical conditions underlying this phenomenon remain unclear. We prove that discrete translational invariance and an equidistant energy spectrum together constitute the necessary and sufficient conditions for perfect chiral circulation. With this criterion established, an exact closed-form Hamiltonian valid for arbitrary $N$-site rings naturally follows. In the minimal three-site ring, we demonstrate two physically distinct realizations: Floquet engineering of a driven open chain that restores translational invariance by equalizing the couplings, and correlated doublon dynamics in an anyon-Hubbard model where fractional statistics intrinsically provide the chiral flux that renders the spectrum equidistant. Our results establish unified physical criteria for perfect chiral circulation and demonstrate their applicability across diverse platforms such as superconducting circuits, cold atoms, classical electrical circuits, and photonic synthetic dimensions.

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arXiv2025

Resonator-assisted single-photon frequency convertion in a conventional waveguide with a giant V-type atom

We propose a scheme to achieve efficient frequency conversion for a single photon propagating in a 1D conventional waveguide by exploiting the quantum interference induced by the scale of a V-type giant atom (GA) characterized by the distance between the two coupling points as well as single-photon transition pathways originated from the coupling between the GA and the resonator. The presence of photons in the resonator triggers the frequency conversion of photons. The scattering spectra and the conversion contrast are studied in both the Markovian and the non-Markovian regimes. The disappearance of frequency conversion is rooted in the complete suppression of the emission from the excited state to either of lower states in the $n+1$ subspace where $n$ is the photon number of the resonator, and the non-Markovicity-induced nonreciprocity is found under specific conditions. Altering the photon number $n$ induces the non-reciprocal transmission of single photons in the waveguide, hence, enhance the conversion probability.

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arXiv2025

Tunable single-photon frequency converter in a waveguide with a giant V-type atom

We study the single-photon scattering in a one-dimensional (1D) waveguide coupled to one transition of a $V$-type giant atom (GA), whose other transition is coherently driven by an classical field. The inelastic scattering of single photons by the GA realizes the single-photon frequency conversion. By applying the Lippmann-Schwinger equation, the scattering coefficients for single photons incident from different directions are obtained, which present different scattering spectra in the Markovian and the non-Markovian regimes. The conversion contrast characterizing the nonreciprocity is also analyzed in both regimes. It is found that the probability of the frequency up- or down-conversion vanishes as long as the emission from either transition pathways for single photons is suppressed, but it is enhanced and even reach unity by introducing the nonreciprocity. It is the quantum self-interference induced by the scale of this two-legged GA and the phase difference between the GA-waveguide couplings that tune the probability of the frequency up- or down-conversion.

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arXiv2025

Controlling the $\mathcal{PT}$ Symmetry Breaking Threshold in Bipartite Lattice Systems with Floquet Topological Edge States

We investigate the control of the parity-time ($\mathcal{PT}$)-symmetry breaking threshold in a periodically driven one-dimensional dimerized lattice with spatially symmetric gain and loss defects. We elucidate the contrasting roles played by Floquet topological edge states in determining the $\mathcal{PT}$ symmetry breaking threshold within the high- and low-frequency driving regimes. In the high-frequency regime, the participation of topological edge states in $\mathcal{PT}$ symmetry breaking is contingent upon the position of the $\mathcal{PT}$-symmetric defect pairs, whereas in the low-frequency regime, their participation is unconditional and independent of the defect pairs placement, resulting in a universal zero threshold. We establish a direct link between the symmetry-breaking threshold and how the spatial profile of the Floquet topological edge states evolves over one driving period. We further demonstrate that lattices with an odd number of sites exhibit unique threshold patterns, in contrast to even-sized systems. Moreover, applying co-frequency periodic driving to the defect pairs, which preserves time-reversal symmetry, can significantly enhance the $\mathcal{PT}$ symmetry-breaking threshold.

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arXiv2025

Generation and Stabilization of Bound States in the Continuum in Dissipative Floquet Optical Lattices

This paper investigates the generation and stabilization of bound states in the continuum (BICs) in a one-dimensional dissipative Floquet lattice. We find a different mechanism for the generation of stable BICs in the open one-dimensional lattice system, which stems from a peculiar dark Floquet state, a state with zero quasi-energy and negligible population on the lossy sites. Our results reveal that the evolutionary stability of BICs resulting from the dark Floquet state can be significantly enhanced, as evidenced by their very low decay rate, by increasing the driving frequency or, counterintuitively, increasing the dissipation strength. We further demonstrate that stable dark Floquet BICs can robustly persist even in nonlinear regimes. The existence of these stable dark Floquet BICs can be attributed to the role of higher-order correction terms in the effective Floquet Hamiltonian derived via the high-frequency expansion (HFE) method. Furthermore, we demonstrate that incorporating non-Hermitian dissipation can extend the parameter regime for the existence of BICs, and the dissipation-induced BICs can lead to complete reflection of wave packets. Our findings provide theoretical support for the experimental realization of stable BICs in dissipative quantum systems.

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arXiv2024

Quantum-classical correspondence of non-Hermitian spin-orbit coupled bosonic junction

We investigate the classical-quantum correspondence of non-Hermitian Spin-orbit (SO)-coupled bosonic junctions, where an effective decay term is introduced in one of the two wells. Starting from the normalized two-point functions, we analytically demonstrate that the mean-field system has a classical Hamiltonian structure, and we successfully derive a non-Hermitian discrete nonlinear Schrödinger (Gross-Pitaevskii) equation. We discover that near the symmetry-breaking phase transition point, the correspondence between classical (mean-field) and quantum dynamics is more likely to break down. When the effective spin-orbit coupling (SOC) strength assumes half-integer values, atomic self-trapping in the non-lossy well definitely occurs, regardless of the system parameters, and the quantum dynamics is insensitive to the number of particles. Additionally, we reveal that in both the mean-field and many-particle models, the SOC effects can greatly promote the synchronous periodic oscillations between the spin-up and spin-down components, and this synchronization dynamics is protected by a symmetry mechanism.

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arXiv2024

Spin-orbit coupling mediated photon-like resonance for a single atom trapped in a symmetric double well

We employ a method involving coherent periodic modulation of Raman laser intensity to induce resonance transitions between energy levels of a spin-orbit coupled atom in a symmetric double-well trap. By integrating photon-assisted tunneling (PAT) technique with spin-orbit coupling (SOC), we achieve resonance transitions between the predefined energy levels of the atom, thereby enabling further precise control of the atom's dynamics. We observe that such photon-like resonance can induce a transition from a localized state to atomic Rabi oscillation between two wells, or effectively reduce tunneling as manifested by a quantum beating phenomenon. Moreover, such resonance transitions have the potential to induce spin flipping in a spin-orbit coupled atom. Additionally, the SOC-mediated transition from multiphoton resonance to fundamental resonance and the SOC-induced resonance suppression are also discovered. In these cases, the analytical results of the effective coupling coefficients of the resonance transition derived from a four-level model can account for the entire dynamics, demonstrating surprisingly good agreement with the numerically exact results based on the realistic continuous model.

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