Griffith Rufo | Searcharxiv

arXiv2025

Domain Wall Control of Topological Qubits in the Kitaev SSH Chain

Zero energy states in one dimensional SSH Kitaev hybrid systems have emerged as promising candidates for topological qubits. In our work, we show that introducing a domain wall into a chain with anisotropic superconducting correlations provides a powerful way to control both the number and the nature of these boundary modes. The defect acts as a digital knob: its presence or absence flips the parity of zero modes and thus decides whether an isolated Majorana exists at the chain ends. This on/off mechanism is significantly more robust and simpler than fine-tuning global parameters such as chemical potential or hopping amplitudes. Moreover, anisotropy provides an additional lever to calibrate the effect of the defect, opening a pathway to architectures where topological qubits can be locally addressed by domain walls. This proposal reframes defects not as imperfections, but as useful resources for quantum information and computation.

cond-mat.mes-hall↗

arXiv2025

Quantum and Semi-Classical Signatures of Dissipative Chaos in the Steady State

We investigate the quantum-classical correspondence in open quantum many-body systems using the SU(3) Bose-Hubbard trimer as a minimal model. Combining exact diagonalization with semiclassical Langevin dynamics, we establish a direct connection between classical trajectories characterized by fixed-point attractors, limit cycles, or chaos and the spectral and structural properties of the quantum steady state. We show that classical dynamical behavior, as quantified by the sign of the Lyapunov exponent, governs the level statistics of the steady-state density matrix: non-positive exponents associated with regular dynamics yield Poissonian statistics, while positive exponents arising from chaotic dynamics lead to Wigner-Dyson statistics. Strong symmetries constrain the system to lower-dimensional manifolds, suppressing chaos and enforcing localization, while weak symmetries preserve the global structure of the phase space and allow chaotic behavior to persist. To characterize phase-space localization, we introduce the phase-space inverse participation ratio IPR, which defines an effective dimension D of the Husimi distribution's support. We find that the entropy scales as $S \propto \ln N^D$, consistently capturing the classical nature of the underlying dynamics. This semiclassical framework, based on stochastic mixtures of coherent states, successfully reproduces not only observable averages but also finer features such as spectral correlations and localization properties. Our results demonstrate that dissipative quantum chaos is imprinted in the steady-state density matrix, much like in closed systems, and that the interplay between dynamical regimes and symmetry constraints can be systematically probed using spectral and phase-space diagnostics. These tools offer a robust foundation for studying ergodicity, localization, and non-equilibrium phases of open quantum systems.

cond-mat.stat-mech↗