We study the one-dimensional frustrated J1-J2 Heisenberg spin-1/2 model under periodic boundary conditions, focusing on quantum criticality induced by competing interactions and parity-dependent frustration. Using quantum discord (QD) and global quantum discord (GQD), we analyze phase transitions in mixed and first excited states, revealing clear parity effects: even-length chains show a single energy level crossing and a sharp derivative anomaly near the singular point, which extrapolates to the thermodynamic infinite-order Berezinskii-Kosterlitz-Thouless phase transition point lambda c(infinity)approximate to 0.241 ( lambda=J2/J1 ) marking the Luttinger liquid to dimerized phase transition; odd-length chains exhibit two crossings but no abrupt transition. This smoothing effect is physically rooted in the true geometric frustration inherent to a periodic ring with an odd number of sites, which prohibits perfect dimerization and drives a comprehensive spectral reorganization and state hybridization among the low-lying excited states under low-energy state truncation. The resulting thermal stability of QD and GQD in odd-length chains, valid within the low-temperature regime, offers insights for the design of quantum memory platforms in frustrated systems. Our results highlight QD and GQD as effective probes of parity-resolved quantum phase transitions in frustrated low-dimensional systems.
We investigate the dynamics of quantum coherence and extractable work for a qubit interacting with a squeezed thermal reservoir within the pure dephasing model. Since the system undergoes decoherence without energy dissipation, the evolution provides a suitable framework for analyzing the direct connection between quantum coherence and ergotropy. Using the exact dephasing dynamics, we study the effects of the reservoir temperature, spectral properties, and squeezing parameters on the coherent and incoherent contributions to ergotropy. Our results show that the decay of quantum coherence is accompanied by a reduction in extractable work, demonstrating the fundamental role of coherence as a thermodynamic resource. In particular, increasing temperature and squeezing strength enhance decoherence and suppress ergotropy, while non-Markovian regimes may partially preserve coherence and work extraction capability. These findings provide insight into the interplay between open-system dynamics and quantum thermodynamic resources in structured squeezed environments.
Topological phases are widely expected to protect quantum information through symmetry-enforced degeneracies, yet the operational mechanisms underlying coherence protection are rarely resolved. We perform a mechanism-resolved study of a logical qubit encoded in the edge modes of the Su–Schrieffer–Heeger (SSH) model, using Lindblad master equation simulations to disentangle two independent protective effects: spatial localization of the edge-state wavefunctions and chiral symmetry pinning of the edge-state degeneracy. By continuously interpolating between chiral symmetry-breaking (on-site) and chiral symmetry-preserving (bond) noise, we find that the topological encoding shows a larger dynamical coherence advantage under on-site noise than under bond noise (protection factors 3.15 versus 2.12). Because the two channels carry different effective dephasing power, we normalize them to equal dissipation power and to equal trivial-encoding decay rate; the on-site advantage persists ( 1.6× ) whenever the dissipation rate exceeds the finite-size edge splitting, so it is not a channel power artifact. The on-site protection factor grows with chain length (from 1.4 to 3.5) and saturates; the saturation value is γ -independent below the bulk gap while the saturation length follows N_sat≃ 2+ln (1.68 w/γ )/ln (w/v) . We derive the logical dephasing rate analytically from the Lindbladian and show that it reproduces the simulated coherence floor with no free parameters. The mechanism is subtle: Chiral symmetry contributes through an exact cancellation of the pure dephasing channel between the two edge states—which we confirm by a chiral-breaking control—while the length dependence is set by the edge hybridization splitting Δ∼ w(v/w)^N , whose scale is the localization length. Neither localization nor symmetry alone is the sole driver; symmetry fixes the height of the coherence floor while localization sets its length dependence. As a hardware benchmark, we execute the Trotterized dynamics on the IBM ibm_kingston superconducting processor: The qualitative dynamical contrast between encodings—monotonic edge population decay versus ballistic bulk oscillation—survives device noise up to a transpiled depth of 222, and a device-calibrated noise simulation with no fitted parameters reproduces the trivial-encoding loss and the depth dependence of the topological loss. This is a proof of execution of the dynamical signature, not a measurement of logical coherence.
The rapid development of quantum communication networks has highlighted the urgent need for physical-layer protection mechanisms that complement cryptographic protocols. While photonic systems provide low-loss transmission and high-fidelity quantum state manipulation, they remain vulnerable to side-channel leakage and electromagnetic probing. Plasmonic nanostructures, on the other hand, offer extreme field confinement and tunable resonance properties, enabling adaptive shielding against external interrogation. In this work, we propose a hybrid plasmonic–photonic cloaking framework designed to enhance the security of quantum communication channels. The architecture integrates metamaterial-based plasmonic layers with photonic waveguides to dynamically suppress scattering signatures, minimize information leakage, and preserve quantum coherence. Analytical modeling and numerical simulations demonstrate that the hybrid cloak achieves attenuation exceeding 40 dB in targeted probing bands while maintaining entanglement visibility above 90
We investigate the Dirac oscillator in the spacetime of a spinning cosmic string in the presence of a uniform magnetic field and an Aharonov–Bohm flux, obtaining exact analytical solutions for the relativistic spectrum and wave functions. The combined effects of curvature, rotation, and electromagnetic flux produce controllable shifts in the effective angular momentum and in the localization properties of the states. We compute the Shannon entropies in coordinate and momentum spaces and show that the geometric and topological parameters act as tunable resources for manipulating quantum uncertainty and information distribution in relativistic systems. Our results reveal how nontrivial spacetime backgrounds can be exploited to engineer quantum–information-relevant features, offering new pathways for relativistic quantum control and entropy-based quantum diagnostics.
