Based on our recently published work [Front. Phys. 21, 093201 (2026)], we extend the analysis to the density-operator evolution of a two-mode entangled quantum system subject to amplitude decay and show that the output state retains the same functional structure as the initial density operator throughout the decay. We further examine the evolutions of several quantum statistical distributions and the von Neumann entropy used to quantify entanglement during the process. This work offers a systematic approach to studying two-mode entangled open systems and yields results on the von Neumann entropy that may help facilitate entanglement measurement.

Quantum secure direct communication (QSDC) enables the direct transmission of confidential information without pre-shared keys. However, device imperfections in practical systems can lead to information leakage. The Trojan-horse attack (THA), a stealthy side-channel threat, steals information by injecting photons into encoding devices and analyzing the reflected light. This paper focuses on the single-photon-based (DL04) protocol, establishing for the first time a comprehensive THA model against it. By combining weak coherent pulse (WCP) sources with the decoy-state method, we systematically analyze the security under THA during both the first and second rounds of transmission, derive analytical expressions for the secrecy message capacity, and quantitatively evaluate the impact of attack strength on system performance through numerical simulations. Our results demonstrate that the system’s security is highly sensitive to the average number of reflected Trojan photons, {\mu }_{\mathrm{o}\mathrm{u}\mathrm{t}}. For a first-round attack, the secrecy message capacity remains nearly identical to the attack-free case when {\mu }_{\mathrm{o}\mathrm{u}\mathrm{t}}\le {10}^{-8}, but drops to zero when {\mu }_{\mathrm{o}\mathrm{u}\mathrm{t}} increases to {10}^{-3}. In contrast, the second round of attacks had a weaker impact. Even at the strongest attack intensity ({\mu }_{\mathrm{o}\mathrm{u}\mathrm{t}}={10}^{-2}), the system could still maintain a certain level of secrecy message capacity. When THA simultaneously targets both the first and second rounds, the overall security of the system is predominantly governed by the more sensitive first-round attack, whose security boundary remains largely comparable to that observed in a single first-round attack scenario. Furthermore, We perform parameter optimization to achieve the optimal secrecy message capacity for each channel attenuation. Our study provides the first quantitative security bound for THA on DL04 protocol, offering practical guidance for encoder isolation requirements in future implementations.

Nonlayered two-dimensional (2D) β-In₂S₃ nanostructures have demonstrated outstanding electronic and optoelectronic properties, which requires its large-scale single-crystalline films to suppress carrier scattering. However, the weak energy for In−S chemical bonds and inherent nonlayered structure with three dimensional bonds make it highly challenging to achieve large area 2D β-In₂S₃ nanoflakes, which is still limited by the high nucleation density and three-dimensional isotropic growth tendency. Herein, we propose a universal strategy of suppressing nucleation and slow-kinetic epitaxial growth of large domain 2D nonlayered β-In₂S₃ nanoflakes via water molecules for the optoelectronic applications. The water molecules acted as the function of partially oxidized In₂S₃ nucleus via mild oxidation, which reduced the nucleation density by approximately three orders of magnitude and enabled the formation of large-area single-crystal with an average domain size of 120 μm and a maximum size approaching 270 μm. The structural characteristics and electronic structures of our β-In₂S₃ samples characterized by various characterization techniques showed unique single-crystalline nature and modified Fermi level properties. Furthermore, the diverse nanostructures of β-In₂S₃ could be precisely tuned from triangular nanosheets to nanowires by controlling the growth conditions. The two-terminal β-In₂S₃ photodetectors exhibited excellent performance with a high photoresponsivity of 44 A·W⁻¹ and a fast response speed with rise and decay times of 6 and 7 ms, respectively, revealing the superior physical properties of large domain 2D β-In₂S₃. This work provides a universal water-assisted strategy for synthesizing large-area 2D non-layered materials and paves the way for significant potential of high-quality large-scale single-crystalline β-In₂S₃ for advanced optoelectronic devices applications.

In nanoscale metal-oxide-semiconductor field-effect transistors (MOSFETs), excess noise has been experimentally observed as the channel length is scaled down. Theoretical analyses indicate that as the channel length decreases, the dominant component of excess noise gradually changes from modified thermal noise to suppressed shot noise. However, no clear quantitative analysis has been provided regarding the specific conditions for this transition. In this paper, based on a device current model, we analyze the transition conditions under which shot noise replaces thermal noise as the dominant component of excess noise. In the modeling process, we comprehensively consider short-channel effects, including the electric field distribution, mobility reduction caused by electron temperature gradients, and the hot-carrier effect. Meanwhile, we use 3D Monte Carlo simulations to analyze the channel current noise components in MOSFETs with different channel lengths, and we simulate the effects of drain–source voltage, gate voltage, temperature, and substrate doping density on the transition of excess noise components. The simulation results show that the transition trend of excess noise components is consistent with predictions from the physical model: the critical channel length for the transition from thermal noise to shot noise in nanoscale MOSFETs is approximately 20 nm. The model and simulation results presented in this paper agree with reported experimental measurements and provide a theoretical foundation for the quantitative analysis of excess noise components in nanoscale MOSFETs.

We investigated the gate-tunable spin transistor structured as a ferromagnet–topological insulator–ferromagnet junction implemented on a zigzag phosphorene nanoribbon. By applying a gate voltage to the device region, the wave vector of the channel can be effectively modulated, thereby shifting the resonance condition of the junction and enabling efficient tuning of the spin-dependent conductance. The conductance of the junction can be switched between e^2/h and 0, corresponding to the ON and OFF states, respectively. Our work demonstrates a feasible strategy for realizing spin transistors and highlights the potential of such systems for future spintronic applications.

We investigate a one-dimensional system featuring simultaneous off-diagonal and diagonal quasiperiodic modulations. By analyzing the fractal dimension, we map out the delocalization−localization phase diagram. We demonstrate that delocalized and localized states can be distinguished via the Wigner distribution, while extended, critical, and localized phases are separated using the Wigner entropy. Furthermore, we explore the quantum thermodynamic properties, revealing that localized states facilitate the emergence of a quantum heater mode, alongside the appearance of a refrigerator mode. In addition, the efficiency of the quantum engine and the coefficient of performance of the quantum refrigerator are analyzed and discussed. These findings enhance our understanding of localization phenomena and expand the thermodynamic applications of quasiperiodic systems.